Accordion

All HIFI First Result Letters (Press the links below to see the papers), (Newest -> Old)

D. A. Neufeld et al., Herschel/HIFI observations of IRC+10216: water vapor in the inner envelope of a carbon-rich AGB star (HIFISTARS)

  1012.1854            HIFISTARS

David A. Neufeld (JHU), Eduardo González-Alfonso (Alcala de Henares), Gary J. Melnick (CfA), Miroslaw Schmidt, Ryszard Szczerba (N. Copernicus Astro. Cntr.), Leen Decin (K.U. Leuven), Alex de Koter (Amsterdam & Utrecht), Fredrik Schöier (Onsala), José Cernicharo (CAB)

We report the results of observations of ten rotational transitions of water vapor toward the carbon-rich AGB (asymptotic giant branch) star IRC+10216 (CW Leonis), carried out with Herschel's HIFI instrument. Each transition was securely detected by means of observations using the dual beam switch mode of HIFI. The measured line ratios imply that water vapor is present in the inner outflow at small distances (few x 1.E+14 cm) from the star, confirming recent results reported by Decin et al. from observations with Herschel's PACS and SPIRE instruments. This finding definitively rules out the hypothesis that the observed water results from the vaporization of small icy objects in circular orbits. The origin of water within the dense C-rich envelope of IRC+10216 remains poorly understood. We derive upper limits on the H2-17O/H2-16O and H2-18O/H2-16O isotopic abundance ratios of ~ 5.E-3 (3 sigma), providing additional constraints on models for the origin of the water vapor in IRC+10216.

E. De Beck et al., Snooping around the big dog: VY CMa as seen with Herschel/HIFI (HIFISTARS)

  1011.6025            HIFISTARS

E. De Beck, L. Decin, K. M. Menten, A. Marston, D. Teyssier, the HIFISTARS team

In the framework of the HIFISTARS guaranteed time key programme, we measured more than 70 molecular emission lines with high signal-to-noise ratio towards VY CMa using the high-resolution HIFI spectrometer on board the Herschel satellite. The kinematic information obtained from the measured water lines supports the hypothesis of multiple outflow components. The observed high-intensity maser lines give no indication for strong polarisation.

Ott et al., The Herschel Data Processing System - HIPE and Pipelines - Up and Running Since the Start of the Mission

  1011.1209           

Stephan Ott, Herschel Science Centre, European Space Agency

The Herschel Space Observatory is the fourth cornerstone mission in the ESA science programme and performs photometry and spectroscopy in the 55 - 672 micron range. The development of the Herschel Data Processing System started in 2002 to support the data analysis for Instrument Level Tests. The Herschel Data Processing System was used for the pre-flight characterisation of the instruments, and during various ground segment test campaigns. Following the successful launch of Herschel 14th of May 2009 the Herschel Data Processing System demonstrated its maturity when the first PACS preview observation of M51 was processed within 30 minutes of reception of the first science data after launch. Also the first HIFI observations on DR21 were successfully reduced to high quality spectra, followed by SPIRE observations on M66 and M74. A fast turn-around cycle between data retrieval and the production of science-ready products was demonstrated during the Herschel Science Demonstration Phase Initial Results Workshop held 7 months after launch, which is a clear proof that the system has reached a good level of maturity. We will summarise the scope, the management and development methodology of the Herschel Data Processing system, present some key software elements and give an overview about the current status and future development milestones.

H. Gupta et al. Detection of OH+ and H2O+ towards Orion KL (HEXOS)

  1009.1450            HEXOS

H. Gupta, P. Rimmer, J. C. Pearson, S. Yu, E. Herbst, N. Harada, E. A. Bergin, D. A. Neufeld, G. J. Melnick, R. Bachiller, W. Baechtold, T. A. Bell, G. A. Blake, E. Caux, C. Ceccarelli, J. Cernicharo, G. Chattopadhyay, C. Comito, S. Cabrit, N. R. Crockett, F. Daniel, E. Falgarone, M. C. Diez-Gonzalez, M.-L. Dubernet, N. Erickson, M. Emprechtinger, P. Encrenaz, M. Gerin, J. J. Gill, T. F. Giesen, J. R. Goicoechea, P. F. Goldsmith, C. Joblin, D. Johnstone, W. D. Langer, B. Larsson, W. B. Latter, R. H. Lin, D. C. Lis, R. Liseau, S. D. Lord, F. W. Maiwald, S. Maret, P. G. Martin, J. Martin-Pintado, K. M. Menten, P. Morris, H. S. P. MĂĽller, J. A. Murphy, L. H. Nordh, M. Olberg, V. Ossenkopf, L. Pagani, M. PĂ©rault, T. G. Phillips, R. Plume, S.-L. Qin, M. Salez, L. A. Samoska, P. Schilke, E. Schlecht, S. Schlemmer, R. Szczerba, J. Stutzki, N. Trappe, F. F. S. van der Tak, C. Vastel, S. Wang, H. W. Yorke, J. Zmuidzinas, A. Boogert, R. GĂĽsten, P. Hartogh, N. Honingh, A. Karpov, J. Kooi, J.-M. Krieg, R. Schieder, P. Zaal

We report observations of the reactive molecular ions OH$^+$, H$_2$O$^+$, and H$_3$O$^+$ towards Orion KL with Herschel/HIFI. All three $N=1-0$ fine-structure transitions of OH$^+$ at 909, 971, and 1033GHz and both fine-structure components of the doublet {\it ortho}-H$_2$O$^+$ $1_{11}-0_{00}$ transition at 1115 and 1139GHz were detected; an upper limit was obtained for H$_3$O$^+$. OH$^+$ and H$_2$O$^+$ are observed purely in absorption, showing a narrow component at the source velocity of 9 kms$^{-1}$, and a broad blueshifted absorption similar to that reported recently for HF and {\it para}-H$_{2}^{18}$O, and attributed to the low velocity outflow of Orion KL. We estimate column densities of OH$^+$ and H$_2$O$^+$ for the 9 km s$^{-1}$ component of $9 \pm 3 \times 10^{12}$cm$^{-2}$ and $7 \pm 2 \times 10^{12}$cm$^{-2}$, and those in the outflow of $1.9 \pm 0.7 \times 10^{13}$cm$^{-2}$ and $1.0 \pm 0.3 \times 10^{13}$cm$^{-2}$. Upper limits of $2.4\times 10^{12}$cm$^{-2}$ and $8.7\times 10^{12}$cm$^{-2}$ were derived for the column densities of {\it ortho} and {\it para}-H$_3$O$^+$ from transitions near 985 and 1657GHz. The column densities of the three ions are up to an order of magnitude lower than those obtained from recent observations of W31C and W49N. The comparatively low column densities may be explained by a higher gas density despite the assumption of a very high ionization rate.

P. Hily-Blant et al. Nitrogen hydrides in the cold envelope of IRAS16293-2422 (CHESS)

  1009.1119            CHESS

Pierre Hily-Blant (LAOG), Sébastien Maret (LAOG), Aurore Bacmann (LAOG), Sandrine Bottinelli (CESR), Bérengère Parise, Emmanuel Caux (CESR), Alexandre Faure (LAOG)

Nitrogen is the fifth most abundant element in the Universe, yet the gas-phase chemistry of N-bearing species remains poorly understood. Nitrogen hydrides are key molecules of nitrogen chemistry. Their abundance ratios place strong constraints on the production pathways and reaction rates of nitrogen-bearing molecules. We observed the class 0 protostar IRAS16293-2422 with the heterodyne instrument HIFI, covering most of the frequency range from 0.48 to 1.78~THz at high spectral resolution. The hyperfine structure of the amidogen radical o-NH2 is resolved and seen in absorption against the continuum of the protostar. Several transitions of ammonia from 1.2 to 1.8~THz are also seen in absorption. These lines trace the low-density envelope of the protostar. Column densities and abundances are estimated for each hydride. We find that NH:NH2:NH3=5:1:300. {Dark clouds chemical models predict steady-state abundances of NH2 and NH3 in reasonable agreement with the present observations, whilst that of NH is underpredicted by more than one order of magnitude, even using updated kinetic rates. Additional modelling of the nitrogen gas-phase chemistry in dark-cloud conditions is necessary before having recourse to heterogen processes.

M. Kama et al. The methanol lines and hot core of OMC2-FIR4, an intermediate-mass protostar, with Herschel-HIFI (CHESS)

  1008.2513            CHESS

M. Kama, C. Dominik, S. Maret, F. van der Tak, E. Caux, C. Ceccarelli, A. Fuente, N. Crimier, S. Lord, A. Bacmann, A. Baudry, T. Bell, M. Benedettini, E.A. Bergin, G.A. Blake, A. Boogert, S. Bottinelli, S. Cabrit, P. Caselli, A. Castets, J. Cernicharo, C. Codella, C. Comito, A. Coutens, K. Demyk, P. Encrenaz, E. Falgarone, M. Gerin, P.F. Goldsmith, F. Helmich, P. Hennebelle, T. Henning, E. Herbst, P. Hily-Blant, T. Jacq, C. Kahane, A. Klotz, W. Langer, B. Lefloch, D. Lis, A. Lorenzani, G. Melnick, B. Nisini, S. Pacheco, L. Pagani, B. Parise, J. Pearson, T. Phillips, M. Salez, P. Saraceno, P. Schilke, K. Schuster, A.G.G.M. Tielens, M.H.D. van der Wiel, C. Vastel, S. Viti, V. Wakelam, A. Walters, F. Wyrowski, H. Yorke, P. Cais, R. GĂĽsten, S. Philipp, T. Klein

In contrast with numerous studies on the physical and chemical structure of low- and high-mass protostars, much less is known about their intermediate-mass counterparts, a class of objects that could help to elucidate the mechanisms of star formation on both ends of the mass range. We present the first results from a rich HIFI spectral dataset on an intermediate-mass protostar, OMC2-FIR4, obtained in the CHESS (Chemical HErschel SurveyS of star forming regions) key programme. The more than 100 methanol lines detected between 554 and 961 GHz cover a range in upper level energy of 40 to 540 K. Our physical interpretation focusses on the hot core, but likely the cold envelope and shocked regions also play a role in reality, because an analysis of the line profiles suggests the presence of multiple emission components. An upper limit of 10^-6 is placed on the methanol abundance in the hot core, using a population diagram, large-scale source model and other considerations. This value is consistent with abundances previously seen in low-mass hot cores. Furthermore, the highest energy lines at the highest frequencies display asymmetric profiles, which may arise from infall around the hot core.

C.M. Persson et al., Nitrogen hydrides in interstellar gas: Herschel/HIFI observations towards G10.6-0.4 (W31C) (PRISMAS)

  1007.2550            PRISMAS

C.M. Persson, J.H. Black, J. Cernicharo, J.R. Goicoechea, G.E. Hassel, E. Herbst, M. Gerin, M. De Luca, T.A. Bell, A. Coutens, E. Falgarone, P.F. Goldsmith, H. Gupta, M. Kazmierczak, D.C. Lis, B. Mookerjea, D.A. Neufeld, J. Pearson, T.G. Phillips, P. Sonnentrucker, J. Stutzki, C. Vastel, S. Yu, F. Boulanger, E. Dartois, P. Encrenaz, T.R. Geballe, T. Giesen, B. Godard, C. Gry, P. Hennebelle, P. Hily-Blant, C. Joblin, R. Kolos, J. Krelowski, J. Martin-Pintado, K. Menten, R. Monje, M. Perault, R. Plume, M. Salez, S. Schlemmer, M. Schmidt, D. Teyssier, I. Peron, P. Cais, P. Gaufre, A. Cros, L. Ravera, P. Morris, S. Lord, P. Planesas

The HIFI instrument on board the Herschel Space Observatory has been used to observe interstellar nitrogen hydrides along the sight-line towards G10.6-0.4 in order to improve our understanding of the interstellar chemistry of nitrogen. We report observations of absorption in NH N=1-0, J=2-1 and ortho-NH2 1_1,1-0_0,0. We also observed ortho-NH3 1_0-0_0, and 2_0-1_0, para-NH3 2_1-1_1, and searched unsuccessfully for NH+. All detections show emission and absorption associated directly with the hot-core source itself as well as absorption by foreground material over a wide range of velocities. All spectra show similar, non-saturated, absorption features, which we attribute to diffuse molecular gas. Total column densities over the velocity range 11-54 km/s are estimated. The similar profiles suggest fairly uniform abundances relative to hydrogen, approximately 6*10^-9, 3*10^-9, and 3*10^-9 for NH, NH2, and NH3, respectively. These abundances are discussed with reference to models of gas-phase and surface chemistry.

J. L. Pineda et al. A Sample of [CII] Clouds Tracing Dense Clouds in Weak FUV Fields observed by Herschel (GOT C+)

  1007.5068            GOT C+

Jorge L. Pineda, Thangasamy Velusamy, William D. Langer, Paul F. Goldsmith, Di Li., Harold W. Yorke

The [CII] fine--structure line at 158um is an excellent tracer of the warm diffuse gas in the ISM and the interfaces between molecular clouds and their surrounding atomic and ionized envelopes. Here we present the initial results from Galactic Observations of Terahertz C+ (GOTC+), a Herschel Key Project devoted to study the [CII] fine structure emission in the galactic plane using the HIFI instrument. We use the [CII] emission together with observations of CO as a probe to understand the effects of newly--formed stars on their interstellar environment and characterize the physical and chemical state of the star-forming gas. We collected data along 16 lines--of--sight passing near star forming regions in the inner Galaxy near longitudes 330 degrees and 20 degrees. We identify fifty-eight [CII] components that are associated with high--column density molecular clouds as traced by 13CO emission. We combine [CII], 12CO, and 13CO observations to derive the physical conditions of the [CII]--emitting regions in our sample of high--column density clouds based on comparison with results from a grid of Photon Dominated Region (PDR) models. From this unbiased sample, our results suggest that most of [CII] emission originates from clouds with H2 volume densities between 10e3.5 and 10e5.5 cm^-3 and weak FUV strength (CHI_0=1-10). We find two regions where our analysis suggests high densities >10e5 cm^-3 and strong FUV fields (CHI=10e4-10e6), likely associated with massive star formation. We suggest that [CII] emission in conjunction with CO isotopes is a good tool to differentiate between regions of massive star formation (high densities/strong FUV fields) and regions that are distant from massive stars (lower densities/weaker FUV fields) along the line--of--sight

C. Joblin et al. Gas morphology and energetics at the surface of PDRs: new insights with Herschel observations of NGC 7023 (WADI)

  1008.1315            WADI

C. Joblin, P. Pilleri, J. Montillaud, A. Fuente, M. Gerin, O. Berné, V. Ossenkopf, J. Le Bourlot, D. Teyssier, J. R. Goicoechea, F. Le Petit, M. Röllig, M. Akyilmaz, A. O. Benz, F. Boulanger, S. Bruderer, C. Dedes, K. France, R. Güsten, A. Harris, T. Klein, C. Kramer, S. D. Lord, P. G. Martin, J. Martin-Pintado, B. Mookerjea, Y. Okada, T. G. Phillips, J. R. Rizzo, R. Simon, J. Stutzki, F. van der Tak, H. W. Yorke, E. Steinmetz, C. Jarchow, P. Hartogh, C. E. Honingh, O. Siebertz, E. Caux, B. Colin

We investigate the physics and chemistry of the gas and dust in dense photon-dominated regions (PDRs), along with their dependence on the illuminating UV field. Using Herschel-HIFI observations, we study the gas energetics in NGC 7023 in relation to the morphology of this nebula. NGC 7023 is the prototype of a PDR illuminated by a B2V star and is one of the key targets of Herschel. Our approach consists in determining the energetics of the region by combining the information carried by the mid-IR spectrum (extinction by classical grains, emission from very small dust particles) with that of the main gas coolant lines. In this letter, we discuss more specifically the intensity and line profile of the 158 micron (1901 GHz) [CII] line measured by HIFI and provide information on the emitting gas. We show that both the [CII] emission and the mid-IR emission from polycyclic aromatic hydrocarbons (PAHs) arise from the regions located in the transition zone between atomic and molecular gas. Using the Meudon PDR code and a simple transfer model, we find good agreement between the calculated and observed [CII] intensities. HIFI observations of NGC 7023 provide the opportunity to constrain the energetics at the surface of PDRs. Future work will include analysis of the main coolant line [OI] and use of a new PDR model that includes PAH-related species.

D. Johnstone et al., HERSCHEL-HIFI spectroscopy of the intermediate mass protostar NGC7129 FIRS 2 (WISH)

  1008.1254            WISH

D. Johnstone, M. Fich, C. McCoey, T.A. van Kempen, A. Fuente, L.E. Kristensen, J. Cernicharo, P. Caselli, R. Visser, R. Plume, G.J. Herczeg, E.F. van Dishoeck, S. Wampfler, R. Bachiller, A. Baudry, M. Benedettini, E. Bergin, A.O. Benz, P. Bjerkeli, G. Blake, S. Bontemps, J. Braine, S. Bruderer, C. Codella, F. Daniel, A.M. di Giorgio, C. Dominik, S.D. Doty, P. Encrenaz, T. Giannini, J.R. Goicoechea, Th. de Graauw, F. Helmich, F. Herpin, M.R. Hogerheijde, T. Jacq, J.K. Jørgensen, B. Larsson, D. Lis, R. Liseau, M. Marseille, G. Melnick, D. Neufeld, B. Nisini, M. Olberg, B. Parise, J. Pearson, C. Risacher, J. Santiago-García, P. Saraceno, R. Shipman, M. Tafalla, F. van der Tak, F. Wyrowski, U.A. Yildiz, E. Caux, N. Honingh, W. Jellema, R. Schieder, D. Teyssier, N. Whyborn

HERSCHEL-HIFI observations of water from the intermediate mass protostar NGC7129 FIRS 2 provide a powerful diagnostic of the physical conditions in this star formation environment. Six spectral settings, covering four H216O and two H218O lines, were observed and all but one H218O line were detected. The four H2 16 O lines discussed here share a similar morphology: a narrower, \approx 6 km/s, component centered slightly redward of the systemic velocity of NGC7129 FIRS 2 and a much broader, \approx 25 km/s component centered blueward and likely associated with powerful outflows. The narrower components are consistent with emission from water arising in the envelope around the intermediate mass protostar, and the abundance of H2O is constrained to \approx 10-7 for the outer envelope. Additionally, the presence of a narrow self-absorption component for the lowest energy lines is likely due to self-absorption from colder water in the outer envelope. The broader component, where the H2O/CO relative abundance is found to be \approx 0.2, appears to be tracing the same energetic region that produces strong CO emission at high J.

U.A. Yildiz et al., Herschel-HIFI observations of high-J CO lines in the NGC 1333 low-mass star-forming region (WISH)

  1008.0867            WISH

Umut A. Yildiz, Ewine F. van Dishoeck, Lars E. Kristensen, Ruud Visser, Jes K. Jørgensen, Greg J. Herczeg, T.A. van Kempen, M.R. Hogerheijde, S.D. Doty, A.O. Benz, S. Bruderer, S.F.Wampfler, E. Deul, R. Bachiller, A. Baudry, M. Benedettini, E. Bergin, P. Bjerkeli, G.A. Blake, S. Bontemps, J. Braine, P. Caselli, J. Cernicharo, C. Codella, F. Daniel, A.M. di Giorgio, C. Dominik, P. Encrenaz, M. Fich, A. Fuente, T. Giannini, J.R. Goicoechea, Th. de Graauw, F. Helmich, F. Herpin, T. Jacq, D. Johnstone, B. Larsson, D. Lis, R. Liseau, F.-C. Liu, M. Marseille, C. McCoey, G. Melnick, D. Neufeld, B. Nisini, M. Olberg, B. Parise, J.C. Pearson, R. Plume, C. Risacher, J. Santiago-Garcia, P. Saraceno, R. Shipman, M. Tafalla, A. G. G. M. Tielens, F. van der Tak, F. Wyrowski, P. Dieleman, W. Jellema, V. Ossenkopf, R. Schieder, and J. Stutzki

Herschel-HIFI observations of high-J lines (up to J_u=10) of 12CO, 13CO and C18O are presented toward three deeply embedded low-mass protostars, NGC 1333 IRAS 2A, IRAS 4A, and IRAS 4B, obtained as part of the Water In Star-forming regions with Herschel (WISH) key program. The spectrally-resolved HIFI data are complemented by ground-based observations of lower-J CO and isotopologue lines. The 12CO 10-9 profiles are dominated by broad (FWHM 25-30 km s^-1) emission. Radiative transfer models are used to constrain the temperature of this shocked gas to 100-200 K. Several CO and 13CO line profiles also reveal a medium-broad component (FWHM 5-10 km s^-1), seen prominently in H2O lines. Column densities for both components are presented, providing a reference for determining abundances of other molecules in the same gas. The narrow C18O 9\u20138 lines probe the warmer part of the quiescent envelope. Their intensities require a jump in the CO abundance at an evaporation temperature around 25 K, thus providing new direct evidence for a CO ice evaporation zone around low-mass protostars.

J. Cernicharo et al. A high resolution line survey of IRC+10216 with Herschel/HIFI, Detection of Warm Silicon Dicarbide (SiC2) (GT1)

  1008.1199            GT1

J. Cernicharo, L.B.F.M. Waters, L. Decin, P. Encrenaz, A.G.G.M. Tielens, M. Agundez, E. De Beck, H.S.P. Muller, J.R. Goicoechea, M. J. Barlow, A. Benz, N. Crimier, F. Daniel, A.M. Di Giorgio, M. Fich, T. Gaier, P. Garcia-Lario, A. De Koter, T. Khouri, R. Liseau, R. Lombaert, N. Erickson, J.R. Pardo, J.C. Pearson, R. Shipman, C. Sanchez-Contreras, D. Teyssier

We present the first results of a high-spectral-resolution survey of the carbon-rich evolved star IRC+10216 that was carried out with the HIFI spectrometer onboard Herschel. This survey covers all HIFI bands, with a spectral range from 488 to 1901GHz. In this letter we focus on the band-1b spectrum, in a spectral range 554.5-636.5GHz, where we identified 130 spectral features with intensities above 0.03 K and a signal-to-noise ratio >5. Detected lines arise from HCN, SiO, SiS, CS, CO, metal-bearing species and, surprisingly, silicon dicarbide (SiC2). We identified 55 SiC2 transitions involving energy levels between 300 and 900 K. By analysing these rotational lines, we conclude that SiC2 is produced in the inner dust formation zone, with an abundance of ~2x10^-7 relative to molecular hydrogen. These SiC2 lines have been observed for the first time in space and have been used to derive an SiC2 rotational temperature of ~204 K and a source-averaged column density of ~6.4x10^15 cm^-2. Furthermore, the high quality of the HIFI data set was used to improve the spectroscopic rotational constants of SiC2.

M. Gerin et al., Interstellar CH absorption in the diffuse interstellar medium along the sight-lines to G10.6-0.4 (W31C), W49N and W51 (PRISMAS)

  NOT IN ASTRO-PH YET!             PRISMAS

M. Gerin et al.

We report the detection of the ground state N, J = 1, 3/2 \u2192 1, 1/2 doublet of the methylidyne radical CH at \u223c 532 GHz and \u223c 536 GHz with the Herschel HIFI instrument along the sight-line to the massive star forming regions G10.6\u20130.4 (W31C), W49N and W51. While the molecular cores associated with these massive star forming regions show emission lines, clouds in the diffuse interstellar medium are detected in absorption against the strong submillimeter background. The combination of hyperfine structure with emission and absorption results in complex profiles, with overlap of the different hyperfine components. The opacities of most of the CH absorption features are linearly correlated with those of CCH, CN and HCO+ in the same velocity intervals. In specific narrow velocity intervals, the opacities of CN, HCO+ deviate from the mean trends, giving rise to more opaque absorption features. We propose that CCH can be used as another tracer of the molecular gas in the absence of better tracers, with [CCH]/[H2] \u223c 3.2 ± 1.1 × 10. The observed [CN]/[CH], [CCH]/[CH] abundance ratios suggest that the bulk of the diffuse matter along the lines of sight has gas densities nH = n(H) + 2n(H2) ranging between 100 and 1000 cm.

C. Ceccarelli et al., Herschel Spectral Surveys of Star Forming Regions - Overview of the 555-636 GHz range (CHESS)

  NOT IN ASTRO-PH YET!             CHESS

C. Ceccarelli et al.

High resolution line spectra of star forming regions are mines of information: they provide unique clues to reconstruct the chemical, dynamical and physical structure of the observed source. In this Letter, we present the first overview results from the Herschel Key Project \u201cChemical Herschel Surveys of Star Forming Regions\u201d, CHESS. We report and discuss observations towards five CHESS targets, one outflow shock spot and four protostars with luminosity from 20 to 2 Ă— 105 : L1157-B1, IRAS16293-2422, OMC2-FIR4, AFGL2591 and NGC6334I. The observations were obtained with the heterodyne spectrometer HIFI on board Herschel, with a spectral resolution of 1 MHz. They cover the frequency range 555-636 GHz, a range largely unexplored before the launch of the Herschel satellite. A comparison of the five spectra highlights spectacular differences in the five sources, for example in the density of methanol lines, or the presence/absence of lines from S-bearing molecules or deuterated species.We discuss how these differences can be attributed to the different star forming mass or evolutionary status

E. Falgarone et al. CH+ (1-0) and 13CH+ (1-0) absorption lines in the direction of massive star-forming regions (PRISMAS)

  NOT IN ASTRO-PH YET!             PRISMAS

E. Falgarone et al.

We report the detection of the ground-state rotational transition of the methylidyne cation CH+ and its isotopologue 13CH+ toward the remote massive star-forming regions W33A, W49N, and W51 with the HIFI instrument onboard the Herschel satellite. Both lines are seen only in absorption against the dust continuum emission of the star-forming regions. The CH+ absorption is saturated over almost the entire velocity ranges sampled by the lines-of-sight that include gas associated with the star-forming regions (SFR) and Galactic foreground material. The CH+ column densities are inferred from the optically thin components. A lower limit of the isotopic ratio [12CH+]/[13CH+]> 35.5 is derived from the absorptions of foreground material toward W49N. The column density ratio, N(CH+)/N(HCO+), is found to vary by at least a factor 10, between 4 and > 40, in the Galactic foreground material. Line-of-sight 12CH+ average abundances relative to total hydrogen are estimated. Their average value, N(CH+)/NH > 2.6 Ă— 10\u22128, is higher than that observed in the solar neighborhood and confirms the high abundances of CH+ in the Galactic interstellar medium. We compare this result to the predictions of turbulent dissipation regions (TDR) models and find that these high abundances can be reproduced for the inner Galaxy conditions. It is remarkable that the range of predicted N(CH+)/N(HCO+) ratios, from 1 to \u223c 50, is comparable to that observed.

G. J. Melnick et al., Herschel observations of EXtra-Ordinary Sources (HEXOS): Observations of H2O and its isotopologues towards Orion KL (HEXOS)

  1007.5470            HEXOS

G. J. Melnick, V. Tolls, D. A. Neufeld, E. A. Bergin, T. G. Phillips, S. Wang, N. R. Crockett, T. A. Bell, G.A. Blake, S. Cabrit, E. Caux, C. Ceccarelli, J. Cernicharo, C. Comito, F. Daniel, M.-L. Dubernet, M. Emprechtinger, P. Encrenaz, E. Falgarone, M. Gerin, T. F. Giesen, J. R. Goicoechea, P. F. Goldsmith, E. Herbst, C. Joblin, D. Johnstone, W. D. Langer, W.D. Latter, D. C. Lis, S. D. Lord, S. Maret, P. G. Martin, K. M. Menten, P. Morris, H. S. P. Muller, J. A. Murphy, V. Ossenkopf, L. Pagani, J. C. Pearson, M. Perault, R. Plume, S.-L. Qin, M. Salez, P. Schilke, S. Schlemmer, J. Stutzki, N. Trappe, F. F. S. van der Tak, C. Vastel, H. W. Yorke, S. Yu, J. Zmuidzinas

We report the detection of more than 48 velocity-resolved ground rotational state transitions of H2(16)O, H2(18)O, and H2(17)O - most for the first time - in both emission and absorption toward Orion KL using Herschel/HIFI. We show that a simple fit, constrained to match the known emission and absorption components along the line of sight, is in excellent agreement with the spectral profiles of all the water lines. Using the measured H2(18)O line fluxes, which are less affected by line opacity than their H2(16)O counterparts, and an escape probability method, the column densities of H2(18)O associated with each emission component are derived. We infer total water abundances of 7.4E-5, 1.0E-5, and 1.6E-5 for the plateau, hot core, and extended warm gas, respectively. In the case of the plateau, this value is consistent with previous measures of the Orion-KL water abundance as well as those of other molecular outflows. In the case of the hot core and extended warm gas, these values are somewhat higher than water abundances derived for other quiescent clouds, suggesting that these regions are likely experiencing enhanced water-ice sublimation from (and reduced freeze-out onto) grain surfaces due to the warmer dust in these sources.

R. Rolffs et al., Reversal of infall in SgrB2(M) revealed by Herschel/HIFI observations of HCN lines at THz frequencies (HEXOS)

  1007.5131            HEXOS

Rainer Rolffs, Peter Schilke, Claudia Comito, E.A. Bergin, F.F.S. van der Tak, D.C. Lis, S.-L. Qin, K.M. Menten, R. Guesten, T.A. Bell, G.A. Blake, E. Caux, C. Ceccarelli, J. Cernicharo, N.R. Crockett, F. Daniel, M.-L. Dubernet, M. Emprechtinger, P. Encrenaz, M. Gerin, T.F. Giesen, J.R. Goicoechea, P.F. Goldsmith, H. Gupta, E. Herbst, C. Joblin, D. Johnstone, W.D. Langer, W.D. Latter, S.D. Lord, S. Maret, P.G. Martin, G.J. Melnick, P. Morris, H.S.P. Mueller, J.A. Murphy, V. Ossenkopf, J.C. Pearson, M. Perault, T.G. Phillips, R. Plume, S. Schlemmer, J. Stutzki, N. Trappe, C. Vastel, S. Wang, H.W. Yorke, S. Yu, J. Zmuidzinas, M.C. Diez-Gonzalez, R. Bachiller, J. Martin-Pintado, W. Baechtold,M. Olberg, L.H. Nordh, J.J. Gill, G. Chattopadhyay

To investigate the accretion and feedback processes in massive star formation, we analyze the shapes of emission lines from hot molecular cores, whose asymmetries trace infall and expansion motions. The high-mass star forming region SgrB2(M) was observed with Herschel/HIFI (HEXOS key project) in various lines of HCN and its isotopologues, complemented by APEX data. The observations are compared to spherically symmetric, centrally heated models with density power-law gradient and different velocity fields (infall or infall+expansion), using the radiative transfer code RATRAN. The HCN line profiles are asymmetric, with the emission peak shifting from blue to red with increasing J and decreasing line opacity (HCN to H$^{13}$CN). This is most evident in the HCN 12--11 line at 1062 GHz. These line shapes are reproduced by a model whose velocity field changes from infall in the outer part to expansion in the inner part. The qualitative reproduction of the HCN lines suggests that infall dominates in the colder, outer regions, but expansion dominates in the warmer, inner regions. We are thus witnessing the onset of feedback in massive star formation, starting to reverse the infall and finally disrupting the whole molecular cloud. To obtain our result, the THz lines uniquely covered by HIFI were critically important.

C. Comito et al., Herschel observations of deuterated water towards Sgr B2(M) (HEXOS)

  1007.5128            HEXOS

Claudia Comito, Peter Schilke, Rainer Rolffs, D.C. Lis, A. Belloche, E.A. Bergin, T.G. Phillips, T.A. Bell, N.R. Crockett, S. Wang, G.A. Blake, E.Caux, C. Ceccarelli, J. Cernicharo, F. Daniel, M.-L. Dubernet, M. Emprechtinger, P. Encrenaz, M. Gerin, T.F. Giesen, J.R. Goicoechea, P.F. Goldsmith, H. Gupta, E. Herbst, C. Joblin, D. Johnstone, W.D. Langer, W.D. Latter, S.D. Lord, S. Maret, P.G. Martin, G.J. Melnick, K.M. Menten, P. Morris, H.S.P. Mueller, J.A. Murphy, D.A. Neufeld, V. Ossenkopf, J.C. Pearson, M. Perault, R. Plume, S.-L. Qin, S. Schlemmer, J. Stutzki, N. Trappe, F.F.S. van der Tak, C. Vastel, H.W. Yorke, S. Yu, M. Olberg, R. Szczerba, B. Larsson, R. Liseau, R.H. Lin, L.A. Samoska, E. Schlecht

Observations of HDO are an important complement for studies of water, because they give strong constraints on the formation processes -- grain surfaces versus energetic process in the gas phase, e.g. in shocks. The HIFI observations of multiple transitions of HDO in Sgr~B2(M) presented here allow the determination of the HDO abundance throughout the envelope, which has not been possible before with ground-based observations only. The abundance structure has been modeled with the spherical Monte Carlo radiative transfer code RATRAN, which also takes radiative pumping by continuum emission from dust into account. The modeling reveals that the abundance of HDO rises steeply with temperature from a low abundance ($2.5\times 10^{-11}$) in the outer envelope at temperatures below 100~K through a medium abundance ($1.5\times 10^{-9}$) in the inner envelope/outer core, at temperatures between 100 and 200~K, and finally a high abundance ($3.5\times 10^{-9}$) at temperatures above 200~K in the hot core.

C. Dedes et al., The origin of the [C II] emission in the S140 PDRs - new insights from HIFI (WADI)

  1007.4957            WADI

C. Dedes, M. Röllig, B. Mookerjea, Y. Okada, V. Ossenkopf, S. Bruderer, A.O. Benz, M. Melchior, C. Kramer, M. Gerin, R. Güsten, M. Akyilmaz, O. Berne, F. Boulanger, G. De Lange, L. Dubbeldam, K. France, A. Fuente, J.R. Goicoechea, A. Harris, R. Huisman, W. Jellema, C. Joblin, T. Klein, F. Le Petit, S. Lord, P. Martin, J. Martin-Pintado, D. A. Neufeld, S. Philipp, T. Phillips, P. Pilleri, J.R. Rizzo, M. Salez, R. Schieder, R. Simon, O. Siebertz, J. Stutzki, F. F. S. van der Tak, D. Teyssier, H. Yorke

Using Herschel's HIFI instrument we have observed [C II] along a cut through S140 and high-J transitions of CO and HCO+ at two positions on the cut, corresponding to the externally irradiated ionization front and the embedded massive star forming core IRS1. The HIFI data were combined with available ground-based observations and modeled using the KOSMA-tau model for photon dominated regions. Here we derive the physical conditions in S140 and in particular the origin of [C II] emission around IRS1. We identify three distinct regions of [C II] emission from the cut, one close to the embedded source IRS1, one associated with the ionization front and one further into the cloud. The line emission can be understood in terms of a clumpy model of photon-dominated regions. At the position of IRS1, we identify at least two distinct components contributing to the [C II] emission, one of them a small, hot component, which can possibly be identified with the irradiated outflow walls. This is consistent with the fact that the [C II] peak at IRS1 coincides with shocked H2 emission at the edges of the outflow cavity. We note that previously available observations of IRS1 can be well reproduced by a single-component KOSMA-tau model. Thus it is HIFI's unprecedented spatial and spectral resolution, as well as its sensitivity which has allowed us to uncover an additional hot gas component in the S140 region.

A. Bacmann et al., First detection of ND in the solar-mass protostar IRAS16293-2422 (CHESS)

  1007.4691            CHESS

A. Bacmann, E. Caux, P. Hily-Blant, B. Parise, L. Pagani, S. Bottinelli, S. Maret, C. Vastel, C. Ceccarelli, J. Cernicharo, T. Henning, A. Castets, A. Coutens, E. A. Bergin, G. A. Blake, N. Crimier, K. Demyk, C. Dominik, M. Gerin, P. Hennebelle, C. Kahane, A. Klotz, G. Melnick, P. Schilke, V. Wakelam, A. Walters, A. Baudry, T. Bell, M. Benedettini, A. Boogert, S. Cabrit, P. Caselli, C. Codella, C. Comito, P. Encrenaz, E. Falgarone, A. Fuente, P. F. Goldsmith, F. Helmich, E. Herbst, T. Jacq, M. Kama, W. Langer, B. Lefloch, D. Lis, S. Lord, A. Lorenzani, D. Neufeld, B. Nisini, S. Pacheco, J. Pearson, T. Phillips, M. Salez, P. Saraceno, K. Schuster, A. G. G. M. Tielens, F. F. S. van der Tak, M. H. D. van der Wiel, S. Viti, F. Wyrowski, H. Yorke, A. Faure, A. Benz, O. Coeur-Joly, A. Cros, R. Guesten, L. Ravera

In the past decade, much progress has been made in characterising the processes leading to the enhanced deuterium fractionation observed in the ISM and in particular in the cold, dense parts of star forming regions such as protostellar envelopes. Very high molecular D/H ratios have been found for saturated molecules and ions. However, little is known about the deuterium fractionation in radicals, even though simple radicals often represent an intermediate stage in the formation of more complex, saturated molecules. The imidogen radical NH is such an intermediate species for the ammonia synthesis in the gas phase. Herschel/HIFI represents a unique opportunity to study the deuteration and formation mechanisms of such species, which are not observable from the ground. We searched here for the deuterated radical ND in order to determine the deuterium fractionation of imidogen and constrain the deuteration mechanism of this species. We observed the solar-mass Class 0 protostar IRAS16293-2422 with the heterodyne instrument HIFI as part of the Herschel key programme CHESS (Chemical HErschel Surveys of Star forming regions). The deuterated form of the imidogen radical ND was detected and securely identified with 2 hyperfine component groups of its fundamental transition in absorption against the continuum background emitted from the nascent protostar. The 3 groups of hyperfine components of its hydrogenated counterpart NH were also detected in absorption. We derive a very high deuterium fractionation with an [ND]/[NH] ratio of between 30 and 100%. The deuterium fractionation of imidogen is of the same order of magnitude as that in other molecules, which suggests that an efficient deuterium fractionation mechanism is at play. We discuss two possible formation pathways for ND, by means of either the reaction of N+ with HD, or deuteron/proton exchange with NH.

N. R. Crockett et al., Herschel observations of EXtra-Ordinary Sources: The Terahertz spectrum of Orion KL seen at high spectral resolution (HEXOS)

  1007.4564            HEXOS

N. R. Crockett, E. A. Bergin, S. Wang, D. C. Lis, T. A. Bell, G. A. Blake, A. Boogert, B. Bumble, S. Cabrit, E. Caux, C. Ceccarelli, J. Cernicharo, C. Comito, F. Daniel, M.-L. Dubernet, M. Emprechtinger, P. Encrenaz, E. Falgarone, M. Gerin, T. F. Giesen, J. R. Goicoechea, P. F. Goldsmith, H. Gupta, R. Gusten, P. Hartogh, F. Helmich, E. Herbst, N. Honingh, C. Joblin, D. Johnstone, A. Karpov, J. H. Kawamura, J. Kooi, J.-M. Krieg, W. D. Langer, W.D. Latter, S. D. Lord, S. Maret, P. G. Martin, G. J. Melnick, K. M. Menten, P. Morris, H. S. P. Muller, J. A. Murphy, D. A. Neufeld, V. Ossenkopf, J. C. Pearson, M. Perault, T. G. Phillips, R. Plume, S.-L. Qin, P. Roelfsema, R. Schieder, P. Schilke, S. Schlemmer, J. Stutzki, F. F. S. van der Tak, A. Tielens, N. Trappe, C. Vastel, H. W. Yorke, S. Yu, J. Zmuidzinas

We present the first high spectral resolution observations of Orion KL in the frequency ranges 1573.4 - 1702.8 GHz (band 6b) and 1788.4 - 1906.8 GHz (band 7b) obtained using the HIFI instrument on board the Herschel Space Observatory. We characterize the main emission lines found in the spectrum, which primarily arise from a range of components associated with Orion KL including the hot core, but also see widespread emission from components associated with molecular outflows traced by H2O, SO2, and OH. We find that the density of observed emission lines is significantly diminished in these bands compared to lower frequency Herschel/HIFI bands.

C. Vastel et al. Ortho-to-para ratio of interstellar heavy water (CHESS)

  1007.4410            CHESS

C. Vastel, C. Ceccarelli, E. Caux, A. Coutens, J. Cernicharo, S. Bottinelli, K. Demyk, A. Faure, L. Wiesenfeld, Y. Scribano, A. Bacmann, P. Hily-Blant, S. Maret, A. Walters, E.A. Bergin, G.A. Blake, A. Castets, N. Crimier, C. Dominik, P. Encrenaz, M. GĂ©rin, P. Hennebelle, C. Kahane, A. Klotz, G. Melnick, L. Pagani, B. Parise, P. Schilke, V. Wakelam, A. Baudry, T. Bell, M. Benedettini, A. Boogert, S. Cabrit, P. Caselli, C. Codella, C. Comito, E. Falgarone, A. Fuente, P.F. Goldsmith, F. Helmich, T. Henning, E. Herbst, T. Jacq, M. Kama, W. Langer, B. Lefloch, D. Lis, S. Lord, A. Lorenzani, D. Neufeld, B. Nisini, S. Pacheco, J. Pearson, T. Phillips, M. Salez, P. Saraceno, K. Schuster, X. Tielens, F. van der Tak, M.H.D. van der Wiel, S. Viti, F. Wyrowski, H. Yorke, P. Cais, J.M. Krieg, M. Olberg, L. Ravera

Despite the low elemental deuterium abundance in the Galaxy, enhanced molecular D/H ratios have been found in the environments of low-mass star forming regions, and in particular the Class 0 protostar IRAS 16293-2422. The CHESS (Chemical HErschel Surveys of Star forming regions) Key Program aims at studying the molecular complexity of the interstellar medium. The high sensitivity and spectral resolution of the HIFI instrument provide a unique opportunity to observe the fundamental 1,1,1 - 0,0,0 transition of the ortho-D2O molecule, inaccessible from the ground, and to determine the ortho-to-para D2O ratio. We have detected the fundamental transition of the ortho-D2O molecule at 607.35 GHz towards IRAS 16293-2422. The line is seen in absorption with a line opacity of 0.62 +/- 0.11 (1 sigma). From the previous ground-based observations of the fundamental 1,1,0 - 1,0,1 transition of para-D2O seen in absorption at 316.80 GHz we estimate a line opacity of 0.26 +/- 0.05 (1 sigma). We show that the observed absorption is caused by the cold gas in the envelope of the protostar. Using these new observations, we estimate for the first time the ortho to para D2O ratio to be lower than 2.6 at a 3 sigma level of uncertainty, to be compared with the thermal equilibrium value of 2:1.

F. Wyrowski et al. Variations in H2O+/H2O ratios toward massive star-forming regions (WISH)

  1007.4370            WISH

F. Wyrowski, F. van der Tak, F. Herpin, A. Baudry, S. Bontemps, L. Chavarria, W. Frieswijk, T. Jacq, M. Marseille, R. Shipman, E.F van Dishoeck, A.O. Benz, P. Caselli, M.R. Hogerheijde, D. Johnstone, , R. Liseau, R. Bachiller, M. Benedettini, , E. Bergin, P. Bjerkeli, G. Blake, J. Braine, S. Bruderer, J. Cernicharo, C. Codella, F. Daniel, , A.M. di Giorgio, C. Dominik, S.D. Doty, P. Encrenaz, M. Fich, A. Fuente, T. Giannini, J.R. Goicoechea, Th. de Graauw, F. Helmich, G.J. Herczeg, J.K. Jørgensen, L.E. Kristensen, B. Larsson, D. Lis, C. McCoey, G. Melnick, B. Nisini, M. Olberg, B. Parise, J.C. Pearson, R. Plume, C. Risacher, J. Santiago, P. Saraceno, M. Tafalla, T.A. van Kempen, R. Visser, S. Wampfler, U.A. Yildiz, J.H. Black, E. Falgarone, M. Gerin, P. Roelfsema, P. Dieleman, D. Beintema, A. De Jonge, N. Whyborn, J. Stutzki, V. Ossenkopf

Early results from the Herschel Space Observatory revealed the water cation H2O+ to be an abundant ingredient of the interstellar medium. Here we present new observations of the H2O and H2O+ lines at 1113.3 and 1115.2 GHz using the Herschel Space Observatory toward a sample of high-mass star-forming regions to observationally study the relation between H2O and H2O+ . Nine out of ten sources show absorption from H2O+ in a range of environments: the molecular clumps surrounding the forming and newly formed massive stars, bright high-velocity outflows associated with the massive protostars, and unrelated low-density clouds along the line of sight. Column densities per velocity component of H2 O+ are found in the range of 10^12 to a few 10^13 cm-2 . The highest N(H2O+) column densities are found in the outflows of the sources. The ratios of H2O+/H2O are determined in a range from 0.01 to a few and are found to differ strongly between the observed environments with much lower ratios in the massive (proto)cluster envelopes (0.01-0.1) than in outflows and diffuse clouds. Remarkably, even for source components detected in H2O in emission, H2O+ is still seen in absorption.

M. Emprechtinger et al., The distribution of water in the high-mass star-forming region NGC 6334 I (CHESS)

  1007.4226            CHESS

M. Emprechtinger, D. C. Lis, T. Bell, T. G. Phillips, P. Schilke, C. Comito, R. Rolffs, F. van der Tak, C. Ceccarelli, H. Aarts, A. Bacmann, A. Baudry, M. Benedettini, E.A. Bergin, G. Blake, A. Boogert, S. Bottinelli, S. Cabrit, P. Caselli, A. Castets, E. Caux, J. Cernicharo, C. Codella, A. Coutens, N. Crimier, K. Demyk, C. Dominik, P. Encrenaz, E. Falgarone, A. Fuente, M. Gerin, P. Goldsmith, F. Helmich, P. Hennebelle, T. Henning, E. Herbst, P. Hily-Blant, T. Jacq, C. Kahane, M. Kama, A. Klotz, J. Kooi, W. Langer, B. Lefloch, A. Loose, S. Lord, A. Lorenzani, S. Maret, G. Melnick, D. Neufeld, B. Nisini, V. Ossenkopf, S. Pacheco, L. Pagani, B. Parise, J. Pearson, C. Risacher, M. Salez, P. Saraceno, K. Schuster, J. Stutzki, X. Tielens, M. van der Wiel, C. Vastel, S. Viti, V. Wakelam, A. Walters, F. Wyrowski, H. Yorke

We present observations of twelve rotational transitions of H2O-16, H2O-18, and H2O-17 toward the massive star-forming region NGC 6334 I, carried out with Herschel/HIFI as part of the guaranteed time key program Chemical HErschel Surveys of Star forming regions (CHESS). We analyze these observations to obtain insights into physical processes in this region. We identify three main gas components (hot core, cold foreground, and outflow) in NGC 6334 I and derive the physical conditions in these components. The hot core, identified by the emission in highly excited lines, shows a high excitation temperature of 200 K, whereas water in the foreground component is predominantly in the ortho- and para- ground states. The abundance of water varies between 4 10^-5 (outflow) and 10^-8 (cold foreground gas). This variation is most likely due to the freeze-out of water molecules onto dust grains. The H2O-18/H2O-17 abundance ratio is 3.2, which is consistent with the O-18/O-17 ratio determined from CO isotopologues. The ortho/para ratio in water appears to be relatively low 1.6(1) in the cold, quiescent gas, but close to the equilibrium value of three in the warmer outflow material (2.5(0.8)).

M.G. Marseille et al., Water abundances in high-mass protostellar envelopes: Herschel observations with HIFI (WISH)

  1007.4119            WISH

M.G. Marseille, F.F.S. van der Tak, F. Herpin, F.Wyrowski, L. Chavarría, B. Pietropaoli, A. Baudry, S. Bontemps, J. Cernicharo, T. Jacq, W. Frieswijk, R. Shipman, E.F. van Dishoeck, R. Bachiller, M. Benedettini, A.O. Benz, E. Bergin, P. Bjerkeli, G.A. Blake, J. Braine, S. Bruderer, P. Caselli, E. Caux, C. Codella, F. Daniel, P. Dieleman, A.M. di Giorgio, C. Dominik, S.D. Doty, P. Encrenaz, M. Fich, A. Fuente, T. Gaier, T. Giannini, J.R. Goicoechea, Th. de Graauw, F. Helmich, G.J. Herczeg, M.R. Hogerheijde, B. Jackson, H. Javadi, W. Jellema, D. Johnstone, J.K. Jørgensen, D. Kester, L.E. Kristensen, B. Larsson, W. Laauwen, D. Lis, R. Liseau, W. Luinge, C. McCoey, A. Megej, G. Melnick, D. Neufeld, B. Nisini, M. Olberg, B. Parise, J.C. Pearson, R. Plume, C. Risacher, P. Roelfsema, J. Santiago-García, P. Saraceno, P. Siegel, J. Stutzki, M. Tafalla, T.A. van Kempen, R. Visser, S.F.Wampfler, and U.A. Yildiz

We derive the dense core structure and the water abundance in four massive star-forming regions which may help understand the earliest stages of massive star formation. We present Herschel-HIFI observations of the para-H2O 1_11-0_00 and 2_02-1_11 and the para-H2-18O 1_11-0_00 transitions. The envelope contribution to the line profiles is separated from contributions by outflows and foreground clouds. The envelope contribution is modelled using Monte-Carlo radiative transfer codes for dust and molecular lines (MC3D and RATRAN), with the water abundance and the turbulent velocity width as free parameters. While the outflows are mostly seen in emission in high-J lines, envelopes are seen in absorption in ground-state lines, which are almost saturated. The derived water abundances range from 5E-10 to 4E-8 in the outer envelopes. We detect cold clouds surrounding the protostar envelope, thanks to the very high quality of the Herschel-HIFI data and the unique ability of water to probe them. Several foreground clouds are also detected along the line of sight. The low H2O abundances in massive dense cores are in accordance with the expectation that high densities and low temperatures lead to freeze-out of water on dust grains. The spread in abundance values is not clearly linked to physical properties of the sources.

L. Chavarria et al., Water in massive star-forming regions: HIFI observations of W3 IRS5 (WISH)

  1007.3986            WISH

L. Chavarria, F. Herpin, T. Jacq, J. Braine, S. Bontemps, A. Baudry, M. Marseille, F. van der Tak, B. Pietropaoli, F. Wyrowski, R. Shipman, W. Frieswijk, E.F. van Dishoeck, J. Cernicharo, R. Bachiller, M. Benedettini, A.O. Benz, E. Bergin, P. Bjerkeli, G.A. Blake, S. Bruderer, P. Caselli, C. Codella, F. Daniel, A.M. di Giorgio, C. Dominik, S.D. Doty, P. Encrenaz, M. Fich, A. Fuente, T. Giannini, J.R. Goicoechea, Th. de Graauw, P. Hartogh, F. Helmich, G.J. Herczeg, M.R. Hogerheijde, D. Johnstone, J.K. Jørgensen, L.E. Kristensen, B. Larsson, D. Lis, R. Liseau, C. McCoey, G. Melnick, B. Nisini, M. Olberg, B. Parise, J.C. Pearson, R. Plume, C. Risacher, J. Santiago-Garcia, P. Saraceno, J. Stutzki R. Szczerba, M. Tafalla, A. Tielens, T.A. van Kempen, R. Visser, S.F. Wampfler, J. Willem, U.A. Yildiz

We present Herschel observations of the water molecule in the massive star-forming region W3 IRS5. The o-H17O 110-101, p-H18O 111-000, p-H2O 22 202-111, p-H2O 111-000, o-H2O 221-212, and o-H2O 212-101 lines, covering a frequency range from 552 up to 1669 GHz, have been detected at high spectral resolution with HIFI. The water lines in W3 IRS5 show well-defined high-velocity wings that indicate a clear contribution by outflows. Moreover, the systematically blue-shifted absorption in the H2O lines suggests expansion, presumably driven by the outflow. No infall signatures are detected. The p-H2O 111-000 and o-H2O 212-101 lines show absorption from the cold material (T ~ 10 K) in which the high-mass protostellar envelope is embedded. One-dimensional radiative transfer models are used to estimate water abundances and to further study the kinematics of the region. We show that the emission in the rare isotopologues comes directly from the inner parts of the envelope (T > 100 K) where water ices in the dust mantles evaporate and the gas-phase abundance increases. The resulting jump in the water abundance (with a constant inner abundance of 10^{-4}) is needed to reproduce the o-H17O 110-101 and p-H18O 111-000 spectra in our models. We estimate water abundances of 10^{-8} to 10^{-9} in the outer parts of the envelope (T < 100 K). The possibility of two protostellar objects contributing to the emission is discussed.

S. Bruderer et al., Herschel-HIFI detections of hydrides towards AFGL 2591 (Envelope emission versus tenuous cloud absorption) (WISH)

  1007.3408            WISH

S. Bruderer, A.O. Benz, E.F. van Dishoeck, M. Melchior, S.D. Doty, F. van der Tak, P. Stäuber, S.F.Wampfler, C. Dedes, U.A. Yildiz, L. Pagani, T. Giannini, Th. de Graauw, N. Whyborn, D. Teyssier, W. Jellema, R. Shipman, R. Schieder, N. Honingh, E. Caux, W. Bächtold, A. Csillaghy, C. Monstein, R. Bachiller, A. Baudry, M. Benedettini, E. Bergin, P. Bjerkeli, G.A. Blake, S. Bontemps, J. Braine, P. Caselli, J. Cernicharo, C. Codella, F. Daniel, A.M. di Giorgio, C. Dominik, P. Encrenaz, M. Fich, A. Fuente, J.R. Goicoechea, F. Helmich, G.J. Herczeg, F. Herpin, M.R. Hogerheijde, T. Jacq, D. Johnstone, J.K. Jørgensen, L.E. Kristensen, B. Larsson, D. Lis, R. Liseau, M. Marseille, C. McCoey, G. Melnick, D. Neufeld, B. Nisini, M. Olberg, B. Parise, J.C. Pearson, R. Plume, C. Risacher, J. Santiago-Garcia, P. Saraceno, R. Shipman, M. Tafalla, T.A. van Kempen, R. Visser, F.Wyrowski

The Heterodyne Instrument for the Far Infrared (HIFI) onboard the Herschel Space Observatory allows the first observations of light diatomic molecules at high spectral resolution and in multiple transitions. Here, we report deep integrations using HIFI in different lines of hydrides towards the high-mass star forming region AFGL 2591. Detected are CH, CH+, NH, OH+, H2O+, while NH+ and SH+ have not been detected. All molecules except for CH and CH+ are seen in absorption with low excitation temperatures and at velocities different from the systemic velocity of the protostellar envelope. Surprisingly, the CH(JF,P = 3/2_2,- - 1/2_1,+) and CH+(J = 1 - 0, J = 2 - 1) lines are detected in emission at the systemic velocity. We can assign the absorption features to a foreground cloud and an outflow lobe, while the CH and CH+ emission stems from the envelope. The observed abundance and excitation of CH and CH+ can be explained in the scenario of FUV irradiated outflow walls, where a cavity etched out by the outflow allows protostellar FUV photons to irradiate and heat the envelope at larger distances driving the chemical reactions that produce these molecules.

A.O. Benz et al., Hydrides in Young Stellar Objects: Radiation tracers in a protostar-disk-outflow system (WISH)

  1007.3370            WISH

A.O. Benz, S. Bruderer, E.F. van Dishoeck, P. Stauber, S.F. Wampfler, M. Melchior, C. Dedes, F. Wyrowski, S.D. Doty, F. van der Tak, W. Bachtold, A. Csillaghy, A. Megej, C. Monstein, M. Soldati, R. Bachiller, A. Baudry, M. Benedettini, E. Bergin, P. Bjerkeli, G.A. Blake, S. Bontemps, J. Braine, P. Caselli, J. Cernicharo, C. Codella, F. Daniel, A.M. di Giorgio, P. Dieleman, C. Dominik, P. Encrenaz, M. Fich, A. Fuente, T. Giannini, J.R. Goicoechea, Th. de Graauw, F. Helmich, G.J. Herczeg, F. Herpin, M.R. Hogerheijde, T. Jacq, W. Jellema, D. Johnstone, J.K. Jørgensen, L.E. Kristensen, B. Larsson, D. Lis, R. Liseau, M. Marseille, C. McCoey, G. Melnick, D. Neufeld, B. Nisini, M. Olberg, V. Ossenkopf, B. Parise, J.C. Pearson, R. Plume, C. Risacher, J. Santiago-Garcia, P. Saraceno, R. Schieder, R. Shipman, J. Stutzki, M. Tafalla, A.G.G.M. Tielens, T.A. van Kempen, R. Visser, and U.A. Yildiz

Context: Hydrides of the most abundant heavier elements are fundamental molecules in cosmic chemistry. Some of them trace gas irradiated by UV or X-rays. Aims: We explore the abundances of major hydrides in W3 IRS5, a prototypical region of high-mass star formation. Methods: W3 IRS5 was observed by HIFI on the Herschel Space Observatory with deep integration (about 2500 s) in 8 spectral regions. Results: The target lines including CH, NH, H3O+, and the new molecules SH+, H2O+, and OH+ are detected. The H2O+ and OH+ J=1-0 lines are found mostly in absorption, but also appear to exhibit weak emission (P-Cyg-like). Emission requires high density, thus originates most likely near the protostar. This is corroborated by the absence of line shifts relative to the young stellar object (YSO). In addition, H2O+ and OH+ also contain strong absorption components at a velocity shifted relative to W3 IRS5, which are attributed to foreground clouds. Conclusions: The molecular column densities derived from observations correlate well with the predictions of a model that assumes the main emission region is in outflow walls, heated and irradiated by protostellar UV radiation.

W. D. Langer et al., C+ detection of warm dark gas in diffuse clouds (GOT C+)

  1007.3048            GOT C+

W. D. Langer, T. Velusamy, J. L. Pineda, P. F. Goldsmith, D. Li, H. W. Yorke

We present the first results of the Herschel open time key program, Galactic Observations of Terahertz C$^+$ (GOT C+) survey of the [CII] fine-structure line at 1.9 THz (158 microns) using the HIFI instrument on Herschel. We detected 146 interstellar clouds along sixteen lines-of-sight towards the inner Galaxy. We also acquired HI and CO isotopologue data along each line-of-sight for analysis of the physical conditions in these clouds. Here we analyze 29 diffuse clouds (A$_{V}$ < 1.3 mag.) in this sample characterized by having [CII] and HI emission, but no detectable CO. We find that [CII] emission is generally stronger than expected for diffuse atomic clouds, and in a number of sources is much stronger than anticipated based on their HI column density. We show that excess [CII] emission in these clouds is best explained by the presence of a significant diffuse warm H$_2$, dark gas, component. This first [CII] 158 micron detection of warm dark gas demonstrates the value of this tracer for mapping this gas throughout the Milky Way and in galaxies.

T. Velusamy et al., [CII] observations of H2 molecular layers in transition clouds (GOT C+)

  1007.3338            GOT C+

T. Velusamy, W. D. Langer, J. L. Pineda, P. F. Goldsmith, D. Li., H. W. Yorke

We present the first results on the diffuse transition clouds observed in [CII] line emission at 158 microns (1.9 THz) towards Galactic longitudes near 340deg (5 LOSs) and 20deg (11 LOSs) as part of the GOT C+ survey. Out of the total 146 [CII] velocity components detected by profile fitting we identify 53 as diffuse molecular clouds with associated $^{12}$CO emission but without $^{13}$CO emission and characterized by A$_V$ < 5 mag. We estimate the fraction of the [CII] emission in the diffuse HI layer in each cloud and then determine the [CII] emitted from the molecular layers in the cloud. We show that the excess [CII] intensities detected in a few clouds is indicative of a thick H$_2$ layer around the CO core. The wide range of clouds in our sample with thin to thick H$_2$ layers suggests that these are at various evolutionary states characterized by the formation of H$_2$ and CO layers from HI and C$^+$, respectively. In about 30% of the clouds the H$_2$ column densities (''dark gas'') traced by the [CII] is 50% or more than that traced by $^{12}$CO emission. On the average about 25% of the total H$_2$ in these clouds is in an H$_2$ layer which is not traced by CO. We use the HI, [CII], and $^{12}$CO intensities in each cloud along with simple chemical models to obtain constraints on the FUV fields and cosmic ray ionization rates.

L.E. Kristensen et al., Water in low-mass star-forming regions with Herschel: HIFI spectroscopy of NGC1333 (WISH)

  1007.3031            WISH

L.E. Kristensen, R. Visser, E.F. van Dishoeck, U.A. Yildiz, S.D. Doty, G.J. Herczeg, F.-C. Liu, B. Parise, J.K. Jørgensen, T.A. van Kempen, C. Brinch, S.F. Wampfler, S. Bruderer, A.O. Benz, M.R. Hogerheijde, E. Deul, R. Bachiller, A. Baudry, M. Benedettini, E.A. Bergin, P. Bjerkeli, G.A. Blake, S. Bontemps, J. Braine, P. Caselli, J. Cernicharo, C. Codella, F. Daniel, Th. de Graauw, A.M. di Giorgio, C. Dominik, P. Encrenaz, M. Fich, A. Fuente, T. Giannini, J.R. Goicoechea, F. Helmich, F. Herpin, T. Jacq, D. Johnstone, M.J. Kaufman, B. Larsson, D. Lis, R. Liseau, M. Marseille, C. McCoey, G. Melnick, D. Neufeld, B. Nisini, M. Olberg, J.C. Pearson, R. Plume, C. Risacher, J. Santiago-Garcia, P. Saraceno, R. Shipman, M. Tafalla, A.G.G.M. Tielens, F. van der Tak, F. Wyrowski, D. Beintema, de Jonge, P. Dieleman, V. Ossenkopf, P. Roelfsema, J. Stutzki, N. Whyborn

'Water In Star-forming regions with Herschel' (WISH) is a key programme dedicated to studying the role of water and related species during the star-formation process and constraining the physical and chemical properties of young stellar objects. The Heterodyne Instrument for the Far-Infrared (HIFI) on the Herschel Space Observatory observed three deeply embedded protostars in the low-mass star-forming region NGC1333 in several H2-16O, H2-18O, and CO transitions. Line profiles are resolved for five H16O transitions in each source, revealing them to be surprisingly complex. The line profiles are decomposed into broad (>20 km/s), medium-broad (~5-10 km/s), and narrow (<5 km/s) components. The H2-18O emission is only detected in broad 1_10-1_01 lines (>20 km/s), indicating that its physical origin is the same as for the broad H2-16O component. In one of the sources, IRAS4A, an inverse P Cygni profile is observed, a clear sign of infall in the envelope. From the line profiles alone, it is clear that the bulk of emission arises from shocks, both on small (<1000 AU) and large scales along the outflow cavity walls (~10 000 AU). The H2O line profiles are compared to CO line profiles to constrain the H2O abundance as a function of velocity within these shocked regions. The H2O/CO abundance ratios are measured to be in the range of ~0.1-1, corresponding to H2O abundances of ~10-5-10-4 with respect to H2. Approximately 5-10% of the gas is hot enough for all oxygen to be driven into water in warm post-shock gas, mostly at high velocities.

C.M. Persson et al., Nitrogen hydrides in interstellar gas: Herschel/HIFI observations towards G10.6-0.4 (W31C) (PRISMAS)

  1007.2550            PRISMAS

C.M. Persson, J.H. Black, J. Cernicharo, J.R. Goicoechea, G.E. Hassel, E. Herbst, M. Gerin, M. De Luca, T.A. Bell, A. Coutens, E. Falgarone, P.F. Goldsmith, H. Gupta, M. Kazmierczak, D.C. Lis, B. Mookerjea, D.A. Neufeld, J. Pearson, T.G. Phillips, P. Sonnentrucker, J. Stutzki, C. Vastel, S. Yu, F. Boulanger, E. Dartois, P. Encrenaz, T.R. Geballe, T. Giesen, B. Godard, C. Gry, P. Hennebelle, P. Hily-Blant, C. Joblin, R. Kolos, J. Krelowski, J. Martin-Pintado, K. Menten, R. Monje, M. Perault, R. Plume, M. Salez, S. Schlemmer, M. Schmidt, D. Teyssier, I. Peron, P. Cais, P. Gaufre, A. Cros, L. Ravera, P. Morris, S. Lord, P. Planesas

The HIFI instrument on board the Herschel Space Observatory has been used to observe interstellar nitrogen hydrides along the sight-line towards G10.6-0.4 in order to improve our understanding of the interstellar chemistry of nitrogen. We report observations of absorption in NH N=1-0, J=2-1 and ortho-NH2 1_1,1-0_0,0. We also observed ortho-NH3 1_0-0_0, and 2_0-1_0, para-NH3 2_1-1_1, and searched unsuccessfully for NH+. All detections show emission and absorption associated directly with the hot-core source itself as well as absorption by foreground material over a wide range of velocities. All spectra show similar, non-saturated, absorption features, which we attribute to diffuse molecular gas. Total column densities over the velocity range 11-54 km/s are estimated. The similar profiles suggest fairly uniform abundances relative to hydrogen, approximately 6*10^-9, 3*10^-9, and 3*10^-9 for NH, NH2, and NH3, respectively. These abundances are discussed with reference to models of gas-phase and surface chemistry.

S.F. Wampfler et al., Herschel observations of the hydroxyl radical (OH) in young stellar objects (WISH)

  1007.2198            WISH

S.F. Wampfler , G.J. Herczeg, S. Bruderer, A.O. Benz, E.F. van Dishoeck, L.E. Kristensen, R. Visser, S.D. Doty, M. Melchior, T.A. van Kempen, U.A. Yildiz, C. Dedes, J.R. Goicoechea, A. Baudry, G. Melnick, R. Bachiller, M. Benedettini, E. Bergin, P. Bjerkeli, G.A. Blake, S. Bontemps, J. Braine, P. Caselli, J. Cernicharo, C. Codella, F. Daniel, A.M. di Giorgio, C. Dominik, P. Encrenaz, M. Fich, A. Fuente, T. Giannini, Th. de Graauw, F. Helmich, F. Herpin, M.R. Hogerheijde, T. Jacq, D. Johnstone, J.K. Jørgensen, B. Larsson, D. Lis, R. Liseau, M. Marseille, C. Mc Coey, D. Neufeld, B. Nisini, M. Olberg, B. Parise, J.C. Pearson, R. Plume, C. Risacher, J. Santiago-Garcia, P. Saraceno, R. Shipman, M. Tafalla, F.F.S. van der Tak, F. Wyrowski, P. Roelfsema, W. Jellema, P. Dieleman, E. Caux, and J. Stutzki

Water in Star-forming regions with Herschel (WISH) is a Herschel Key Program investigating the water chemistry in young stellar objects (YSOs) during protostellar evolution. Hydroxyl (OH) is one of the reactants in the chemical network most closely linked to the formation and destruction of H2O. High-temperature chemistry connects OH and H2O through the OH + H2 <-> H2O + H reactions. Formation of H2O from OH is efficient in the high-temperature regime found in shocks and the innermost part of protostellar envelopes. Moreover, in the presence of UV photons, OH can be produced from the photo-dissociation of H2O. High-resolution spectroscopy of the OH 163.12 micron triplet towards HH 46 and NGC 1333 IRAS 2A was carried out with the Heterodyne Instrument for the Far Infrared (HIFI) on board Herschel. The low- and intermediate-mass YSOs HH 46, TMR 1, IRAS 15398-3359, DK Cha, NGC 7129 FIRS 2, and NGC 1333 IRAS 2A were observed with the Photodetector Array Camera and Spectrometer (PACS) in four transitions of OH and two [OI] lines. The OH transitions at 79, 84, 119, and 163 micron and [OI] emission at 63 and 145 micron were detected with PACS towards the class I low-mass YSOs as well as the intermediate-mass and class I Herbig Ae sources. No OH emission was detected from the class 0 YSO NGC 1333 IRAS 2A, though the 119 micron was detected in absorption. With HIFI, the 163.12 micron was not detected from HH 46 and only tentatively detected from NGC 1333 IRAS 2A. The combination of the PACS and HIFI results for HH 46 constrains the line width (FWHM > 11 km/s) and indicates that the OH emission likely originates from shocked gas. This scenario is supported by trends of the OH flux increasing with the [OI] flux and the bolometric luminosity. Similar OH line ratios for most sources suggest that OH has comparable excitation temperatures despite the different physical properties of the sources.

E. A. Bergin et al., Herschel observations of Extra-Ordinary Sources: The Present and Future of Spectral Surveys with Herschel/HIFI (HEXOS)

  1007.2172            HEXOS

E. A. Bergin, T. G. Phillips, C. Comito, N. R. Crockett, D. C. Lis, P. Schilke, S. Wang, T. A. Bell, G.A. Blake, B. Bumble, E. Caux, S. Cabrit, C. Ceccarelli, J. Cernicharo, F. Daniel, Th. de Graauw, M.-L. Dubernet, M. Emprechtinger, P. Encrenaz, E. Falgarone, M. Gerin, T. F. Giesen, J. R. Goicoechea, P. F. Goldsmith, H. Gupta, P. Hartogh, F. P. Helmich, E. Herbst, C. Joblin, D. Johnstone, J. H. Kawamura, W. D. Langer, W. B. Latter, S. D. Lord, S. Maret, P. G. Martin, G. J. Melnick, K. M. Menten, P. Morris, H. S. P. Muller, J. A. Murphy, D. A. Neufeld, V. Ossenkopf, L. Pagani, J. C. Pearson, M. Perault, R. Plume, P. Roelfsema, S.-L. Qin, M. Salez, S. Schlemmer, J. Stutzki, A. G. G. M. Tielens, N. Trappe, F. F. S. van der Tak, C. Vastel, H. W. Yorke, S. Yu, J. Zmuidzinas

We present initial results from the Herschel GT key program: Herschel observations of EXtra-Ordinary Sources (HEXOS) and outline the promise and potential of spectral surveys with Herschel/HIFI. The HIFI instrument offers unprecedented sensitivity, as well as continuous spectral coverage across the gaps imposed by the atmosphere, opening up a largely unexplored wavelength regime to high-resolution spectroscopy. We show the spectrum of Orion KL between 480 and 560 GHz and from 1.06 to 1.115 THz. From these data, we confirm that HIFI separately measures the dust continuum and spectrally resolves emission lines in Orion KL. Based on this capability we demonstrate that the line contribution to the broad-band continuum in this molecule-rich source is ~20-40% below 1 THz and declines to a few percent at higher frequencies. We also tentatively identify multiple transitions of HD18O in the spectra. The first detection of this rare isotopologue in the interstellar medium suggests that HDO emission is optically thick in the Orion hot core with HDO/H2O ~ 0.02. We discuss the implications of this detection for the water D/H ratio in hot cores.

T.G. Phillips et al., Herschel observations of extra-ordinary sources: Detection of Hydrogen Fluoride in absorption towards Orion KL (HEXOS)

  1007.2149            HEXOS

T.G. Phillips, E.A. Bergin, D.C. Lis, D.A. Neufeld, T.A. Bell, S.Wang, N.R. Crockett, M. Emprechtinger, G.A. Blake, E. Caux, C. Ceccarelli, J. Cernicharo, C. Comito, F. Daniel, M.-L. Dubernet, P. Encrenaz, M. Gerin, T. F. Giesen, J. R. Goicoechea, P. F. Goldsmith, E. Herbst, C. Joblin, D. Johnstone, W. D. Langer, W.D. Latter, S. D. Lord, S. Maret, P. G. Martin, G. J. Melnick, K. M. Menten, P. Morris, H. S. P. Muller, J. A. Murphy, V. Ossenkopf, J. C. Pearson, M. Perault, R. Plume, S.-L. Qin, P. Schilke, S. Schlemmer, J. Stutzki, N. Trappe, F. F. S. van der Tak, C. Vastel, H. W. Yorke, S. Yu, J. Zmuidzinas, A. Boogert, R. Gusten, P. Hartogh, N. Honingh, A. Karpov, J. Kooi, J.-M. Krieg, R. Schieder

We report a detection of the fundamental rotational transition of hydrogen fluoride in absorption towards Orion KL using Herschel/HIFI. After the removal of contaminating features associated with common molecules ("weeds"), the HF spectrum shows a P-Cygni profile, with weak redshifted emission and strong blue-shifted absorption, associated with the low-velocity molecular outflow. We derive an estimate of 2.9 x 10^13 cm^-2 for the HF column density responsible for the broad absorption component. Using our best estimate of the H2 column density within the low-velocity molecular outflow, we obtain a lower limit of ~1.6 x 10^-10 for the HF abundance relative to hydrogen nuclei, corresponding to 0.6% of the solar abundance of fluorine. This value is close to that inferred from previous ISO observations of HF J=2--1 absorption towards Sgr B2, but is in sharp contrast to the lower limit of 6 x 10^-9 derived by Neufeld et al. (2010) for cold, foreground clouds on the line of sight towards G10.6-0.4.

P. Sonnentrucker et al., Detection of HF absorption in diffuse molecular clouds with Herschel/HIFI: a ubiquitous tracer of molecular gas. (PRISMAS)

  1007.2148            PRISMAS

P. Sonnentrucker, D. A. Neufeld, T. G. Phillips, M. Gerin, D. C. Lis, M. De Luca, J. R. Goicoechea, J. H. Black, T.A. Bell, F. Boulanger, J. Cernicharo, A. Coutens, E. Dartois, M. Kazmierczak, P. Encrenaz, E. Falgarone, T. R. Geballe, T. Giesen, B. Godard, P. F. Goldsmith, C. Gry, H. Gupta, P. Hennebelle, E. Herbst, P. Hily-Blant, C. Joblin, R. Kolos, J. Krelowski, J. Mart\in-Pintado, K. M. Menten, R. Monje, B. Mookerjea, J. Pearson, M. Perault, C. M. Persson, R. Plume, M. Salez, S. Schlemmer, M. Schmidt, J. Stutzki, D. Teyssier, C. Vastel, S. Yu, E. Caux, R. Gusten, W. A. Hatch, T. Klein, I. Mehdi, P. Morris, J. S. Ward

We discuss the detection of absorption by interstellar hydrogen fluoride (HF) along the sight line to the submillimeter continuum sources W49N and W51. We have used Herschel's HIFI instrument in dual beam switch mode to observe the 1232.4762 GHz J = 1 - 0 HF transition in the upper sideband of the band 5a receiver. We detected foreground absorption by HF toward both sources over a wide range of velocities. Optically thin absorption components were detected on both sight lines, allowing us to measure - as opposed to obtain a lower limit on - the column density of HF for the first time. As in previous observations of HF toward the source G10.6-0.4, the derived HF column density is typically comparable to that of water vapor, even though the elemental abundance of oxygen is greater than that of fluorine by four orders of magnitude. We used the rather uncertain N(CH)-N(H2) relationship derived previously toward diffuse molecular clouds to infer the molecular hydrogen column density in the clouds exhibiting HF absorption. Within the uncertainties, we find that the abundance of HF with respect to H2 is consistent with the theoretical prediction that HF is the main reservoir of gas-phase fluorine for these clouds. Thus, hydrogen fluoride has the potential to become an excellent tracer of molecular hydrogen, and provides a sensitive probe of clouds of small H2 column density. Indeed, the observations of hydrogen fluoride reported here reveal the presence of a low column density diffuse molecular cloud along the W51 sight line, at an LSR velocity of ~ 24kms-1, that had not been identified in molecular absorption line studies prior to the launch of Herschel.

E. Bergin et al., Sensitive limits on the abundance of cold water vapor in the DM Tau protoplanetary disk (WISH)

  1007.2129            WISH

E. Bergin, M.R. Hogerheijde, C. Brinch, J. Fogel, U.A. Yildiz , L.E. Kristensen, E.F. van Dishoeck, T.A. Bell, G.A. Blake, J. Cernicharo, C. Dominik, D. Lis, G. Melnick, D. Neufeld, O. Panic, J.C. Pearson, R. Bachiller, A. Baudry, M. Benedettini, A.O. Benz, P. Bjerkeli, S. Bontemps, J. Braine, S. Bruderer, P. Caselli, C. Codella, F. Daniel, A.M. di Giorgio, S.D. Doty, P. Encrenaz21 , M. Fich, A. Fuente, T. Giannini, J.R. Goicoechea, Th. de Graauw, F. Helmich, G.J. Herczeg, F. Herpin, T. Jacq, D. Johnstone, J.K. Jørgensen, B. Larsson, R. Liseau, M. Marseille, C. Mc Coey, B. Nisini, M. Olberg, B. Parise, R. Plume, C. Risacher, J. Santiago-Garcia, P. Saraceno, R. Shipman, M. Tafalla, T.A. van Kempen, R. Visser, S.F. Wampfler, F. Wyrowski, F. van der Tak, W. Jellema, A.G.G.M. Tielens, P. Hartogh, J. Stutzki, and R. Szczerba

We performed a sensitive search for the ground-state emission lines of ortho- and para-water vapor in the DM Tau protoplanetary disk using the Herschel/HIFI instrument. No strong lines are detected down to 3sigma levels in 0.5 km/s channels of 4.2 mK for the 1_{10}--1_{01} line and 12.6 mK for the 1_{11}--0_{00} line. We report a very tentative detection, however, of the 1_{10}--1_{01} line in the Wide Band Spectrometer, with a strength of T_{mb}=2.7 mK, a width of 5.6 km/s and an integrated intensity of 16.0 mK km/s. The latter constitutes a 6sigma detection. Regardless of the reality of this tentative detection, model calculations indicate that our sensitive limits on the line strengths preclude efficient desorption of water in the UV illuminated regions of the disk. We hypothesize that more than 95-99% of the water ice is locked up in coagulated grains that have settled to the midplane.

S.-L. Qin et al., Herschel observations of extra-ordinary sources: Detecting spiral arm clouds by CH absorption lines (HEXOS)

  1007.1867            HEXOS

S.-L. Qin, P. Schilke, C. Comito, T. Möller, R. Rolffs, H.S.P. Müller, A. Belloche, K. M. Menten, D. C. Lis, T.G. Phillips, E. A. Bergin, T. A. Bell, N. R. Crockett, G. A. Blake, S. Cabrit, E. Caux, C. Ceccarelli, J. Cernicharo, F. Daniel, M.-L. Dubernet, M. Emprechtinger, P. Encrenaz, E. Falgarone, M. Gerin, T. F. Giesen, J. R. Goicoechea, P. F. Goldsmith, H. Gupta, E. Herbst, C. Joblin, D. Johnstone, W. D. Langer, S.D. Lord, S. Maret, P.G. Martin, G.J. Melnick, P. Morris, J.A. Murphy, D.A. Neufeld, V. Ossenkopf, L. Pagani, J. C. Pearson, M. Pérault, R. Plume, M. Salez, S. Schlemmer, J. Stutzki, N. Trappe, F.F.S. van der Tak, C. Vastel, S. Wang, H.W.Yorke, S. Yu, J. Zmuidzinas, A. Boogert, R. Güsten, P. Hartogh, N. Honingh, A. Karpov, J. Kooi, J.M. Krieg, R. Schieder, M.C. Diez-Gonzalez, R. Bachille, J. Martin-Pintado, W. Baechtold, M. Olberg, L.H. Nordh, J.L. Gill, G. Chattopadhyay

We have observed CH absorption lines ($J=3/2, N=1 \leftarrow J=1/2, N=1$) against the continuum source Sgr~B2(M) using the \textit{Herschel}/HIFI instrument. With the high spectral resolution and wide velocity coverage provided by HIFI, 31 CH absorption features with different radial velocities and line widths are detected and identified. The narrower line width and lower column density clouds show `spiral arm' cloud characteristics, while the absorption component with the broadest line width and highest column density corresponds to the gas from the Sgr~B2 envelope. The observations show that each `spiral arm' harbors multiple velocity components, indicating that the clouds are not uniform and that they have internal structure. This line-of-sight through almost the entire Galaxy offers unique possibilities to study the basic chemistry of simple molecules in diffuse clouds, as a variety of different cloud classes are sampled simultaneously. We find that the linear relationship between CH and H$_2$ column densities found at lower $A_V$ by UV observations does not continue into the range of higher visual extinction. There, the curve flattens, which probably means that CH is depleted in the denser cores of these clouds.

V. Bujarrabal et al., Herschel/HIFI observations of high-J CO transitions in the protoplanetary nebula CRL618 (HIFISTARS)

  1007.1570            HIFISTARS

V. Bujarrabal, J. Alcolea, R. Soria-Ruiz, P. Planesas, D. Teyssier, A.P. Marston, J. Cernicharo, L. Decin, C. Dominik, K. Justtanont, A. de Koter, G. Melnick, K.M. Menten, D.A. Neufeld, H. Olofsson, M. Schmidt, F.L. Schoier, R. Szczerba, L.B.F.M. Waters, G. Quintana-Lacaci, R. Gusten, J.D. Gallego, M.C. Diez-Gonzalez, A. Barcia, I. Lopez-Fernandez, K. Wildeman, A.G.G.M. Tielens, K. Jacobs

We performed Herschel/HIFI observations of several CO lines in the far-infrared/sub-mm in the protoplanetary nebula CRL618. The high spectral resolution provided by HIFI allows measurement of the line profiles. Since the dynamics and structure of the nebula is well known from mm-wave interferometric maps, it is possible to identify the contributions of the different nebular components (fast bipolar outflows, double shells, compact slow shell) to the line profiles. The observation of these relatively high-energy transitions allows an accurate study of the excitation conditions in these components, particularly in the warm ones, which cannot be properly studied from the low-energy lines. The 12CO J=16-15, 10-9, and 6-5 lines are easily detected in this source. 13CO J=10-9 and 6-5 are also detected. Wide profiles showing spectacular line wings have been found, particularly in 12CO 16-15. Other lines observed simultaneously with CO are also shown. Our analysis of the CO high-J transitions, when compared with the existing models, confirms the very low expansion velocity of the central, dense component, which probably indicates that the shells ejected during the last AGB phases were driven by radiation pressure under a regime of maximum transfer of momentum. No contribution of the diffuse halo found from mm-wave data is identified in our spectra, because of its low temperature. We find that the fast bipolar outflow is quite hot, much hotter than previously estimated; for instance, gas flowing at 100 km/s must have a temperature higher than ~ 200 K. Probably, this very fast outflow, with a kinematic age < 100 yr, has been accelerated by a shock and has not yet cooled down. The double empty shell found from mm-wave mapping must also be relatively hot, in agreement with the previous estimate.

K. Justtanont et al., A HIFI preview of warm molecular gas around chi Cyg : first detection of H2O emission toward an S-type AGB star (HIFISTARS)

  1007.1536            HIFISTARS

K. Justtanont, L. Decin, F.L. Schoier, M. Maercker, H. Olofsson, V. Bujarrabal, A.P. Marston, D. Teyssier, J. Alcolea, J. Cernicharo, C. Dominik, A. de Koter, G. Melnick, K. Menten, D. Neufeld, P. Planesas, M. Schmidt, R. Szczerba, R. Waters, Th. de Graauw, N. Whyborn, T. Finn, F. Helmich, O. Siebertz, F. Schmulling, V. Ossenkopf, R. Lai

A set of new, sensitive, and spectrally resolved, sub-millimeter line observations are used to probe the warm circumstellar gas around the S-type AGB star chi Cyg. The observed lines involve high rotational quantum numbers, which, combined with previously obtained lower-frequency data, make it possible to study in detail the chemical and physical properties of, essentially, the entire circumstellar envelope of chi Cyg. The data were obtained using the HIFI instrument aboard Herschel, whose high spectral resolution provides valuable information about the line profiles. Detailed, non-LTE, radiative transfer modelling, including dust radiative transfer coupled with a dynamical model, has been performed to derive the temperature, density, and velocity structure of the circumstellar envelope. We report the first detection of circumstellar H2O rotational emission lines in an S-star. Using the high-J CO lines to derive the parameters for the circumstellar envelope, we modelled both the ortho- and para-H2O lines. Our modelling results are consistent with the velocity structure expected for a dust-driven wind. The derived total H2O abundance (relative to H2) is (1.1 +/- 0.2)E-5, much lower than that in O-rich stars. The derived ortho-to-para ratio of 2.1 +/- 0.6 is close to the high-temperature equilibrium limit, consistent with H2O being formed in the photosphere.

M.H.D. van der Wiel et al., Herschel/HIFI obs. of spectrally resolved methylidyne signatures toward the high-mass star forming core NGC6334I (CHESS)

  1007.1539            CHESS

M.H.D. van der Wiel, F.F.S. van der Tak, D.C. Lis, E.A. Bergin, C. Comito, M. Emprechtinger, P. Schilke, E. Caux, C. Ceccarelli, A. Baudry, P.F. Goldsmith, E. Herbst, W. Langer, S. Lord, D. Neufeld, J. Pearson, T. Philips, R. Rolffs, H. Yorke, A. Bacmann, M. Benedettini, G.A. Blake, A. Boogert, S. Bottinelli, S. Cabrit, P. Caselli, A. Castets, J. Cernicharo, C. Codella, A. Coutens, N. Crimier, K. Demyk, C. Dominik, P. Encrenaz, E. Falgarone, A. Fuente, M. Gerin, F. Helmich, P. Hennebelle, T. Henning, P. Hily-Blant, T. Jacq, C. Kahane, M. Kama, A. Klotz, B. Lefloch, A. Lorenzani, S. Maret, G. Melnick, B. Nisini, S. Pacheco, L. Pagani, B. Parise, M. Salez, P. Saraceno, K. Schuster, A.G.G.M. Tielens, C. Vastel, S. Viti, V. Wakelam, A. Walters, F. Wyrowski, K. Edwards, J. Zmuidzinas, P. Morris, L.A. Samoska, D. Teyssier

In contrast to extensively studied dense star-forming cores, little is known about diffuse gas surrounding star-forming regions. We study molecular gas in the high-mass star-forming region NGC6334I, which contains diffuse, quiescent components that are inconspicuous in widely used molecular tracers such as CO. We present Herschel/HIFI observations of CH toward NGC6334I observed as part of the CHESS key program. HIFI resolves the hyperfine components of its J=3/2-1/2 transition, observed in both emission and absorption. The CH emission appears close to the systemic velocity of NGC6334I, while its measured linewidth of 3 km/s is smaller than previously observed in dense gas tracers such as NH3 and SiO. The CH abundance in the hot core is 7 10^-11, two to three orders of magnitude lower than in diffuse clouds. While other studies find distinct outflows in, e.g., CO and H2O toward NGC6334I, we do not detect outflow signatures in CH. To explain the absorption signatures, at least two absorbing components are needed at -3.0 and +6.5 km/s with N(CH)=7 10^13 and 3 10^13 cm^-2. Two additional absorbing clouds are found at +8.0 and 0.0 km/s, both with N(CH)=2 10^13 cm^-2. Turbulent linewidths for the four absorption components vary between 1.5 and 5.0 km/s in FWHM. We constrain physical properties of our CH clouds by matching our CH absorbers with other absorption signatures. In the hot core, molecules such as H2O and CO trace gas that is heated and dynamically influenced by outflow activity, whereas CH traces more quiescent material. The four CH absorbers have column densities and turbulent properties consistent with diffuse clouds: two are located near NGC6334, and two are unrelated foreground clouds. Local density and dynamical effects influence the chemical composition of physical components of NGC6334, causing some components to be seen in CH but not in other tracers, and vice versa.

A. Fuente et al., Herschel observations in the ultracompact HII region Mon R2: Water in dense Photon-dominated regions (PDRs) (WADI)

  1007.1523            WADI

A. Fuente, O.Berne, J. Cernicharo, J.R. Rizzo, M.Gonzalez-Garcia, J.R. Goicoechea, P. Pilleri, V. Ossenkopf, M. Gerin, R. Gusten, M. Akyilmaz, A.O. Benz, F. Boulanger, S. Bruderer, C. Dedes, K. France, S. Garcia-Burillo, A. Harris, C. Joblin, T. Klein, C. Kramer, F. Le Petit, S.D. Lord, P.G. Martin, J. Martin-Pintado, B. Mookerjea, D.A. Neufeld, Y. Okada, J. Pety, T.G. Phillips, M. Rollig, R. Simon, J. Stutzki, F. van der Tak, D. Teyssier, A. Usero, H. Yorke, K. Schuster, M. Melchior, A. Lorenzani, R. Szczerba, M. Fich, C. McCoey, J. Pearson, P. Dieleman

Mon R2, at a distance of 830 pc, is the only ultracompact HII region (UC HII) where the photon-dominated region (PDR) between the ionized gas and the molecular cloud can be resolved with Herschel. HIFI observations of the abundant compounds 13CO, C18O, o-H2-18O, HCO+, CS, CH, and NH have been used to derive the physical and chemical conditions in the PDR, in particular the water abundance. The 13CO, C18O, o-H2-18O, HCO+ and CS observations are well described assuming that the emission is coming from a dense (n=5E6 cm-3, N(H2)>1E22 cm-2) layer of molecular gas around the UC HII. Based on our o-H2-18O observations, we estimate an o-H2O abundance of ~2E-8. This is the average ortho-water abundance in the PDR. Additional H2-18O and/or water lines are required to derive the water abundance profile. A lower density envelope (n~1E5 cm-3, N(H2)=2-5E22 cm-2) is responsible for the absorption in the NH 1_1-0_2 line. The emission of the CH ground state triplet is coming from both regions with a complex and self-absorbed profile in the main component. The radiative transfer modeling shows that the 13CO and HCO+ line profiles are consistent with an expansion of the molecular gas with a velocity law, v_e =0.5 x (r/Rout)^{-1} km/s, although the expansion velocity is poorly constrained by the observations presented here.

D. C. Lis et al., Herschel/HIFI measurements of the ortho/para ratio in water towards Sagittarius B2(M) and W31C (HEXOS, PRISMAS)

  1007.1466            HEXOS, PRISMAS

D. C. Lis, T. G. Phillips, P. F. Goldsmith, D. A. Neufeld, E. Herbst, C. Comito, P. Schilke, H. S. P. Muller, E. A. Bergin, M. Gerin, T. A. Bell, M. Emprechtinger, J. H. Black, G. A. Blake, F. Boulanger, S. Cabrit, E. Caux, C. Ceccarelli, J. Cernicharo, A. Coutens, N. R. Crockett, F. Daniel, E. Dartois, M. De Luca, M.-L. Dubernet, P. Encrenaz, E. Falgarone, T. R. Geballe, B. Godard, T. F. Giesen, J. R. Goicoechea, C. Gry, H. Gupta, P. Hennebelle, P. Hily-Blant, R. Kolos, J. Krelowski, C. Joblin, D. Johnstone, M. Kazmierczak, S. D. Lord, S. Maret, P. G. Martin, J. Martin-Pintado, G. J. Melnick, K. M. Menten, R. Monje, B. Mookerjea, P. Morris, J. A. Murphy, V. Ossenkopf, L. Pagani, J. C. Pearson, M. Perault, C. Persson, R. Plume, S.-L. Qin, M. Salez, S. Schlemmer, M. Schmidt, P. Sonnentrucker, J. Stutzki, D. Teyssier, N. Trappe, F. F. S. van der Tak, C. Vastel, S. Wang, H. W. Yorke, S. Yu, J. Zmuidzinas, A. Boogert, N. Erickson, A. Karpov, J. Kooi, F. W. Maiwald, R. Schieder, and P. Zaal

We present Herschel/HIFI observations of the fundamental rotational transitions of ortho- and para-H$_2^{16}$O and H$_2^{18}$O in absorption towards Sagittarius~B2(M) and W31C. The ortho/para ratio in water in the foreground clouds on the line of sight towards these bright continuum sources is generally consistent with the statistical high-temperature ratio of 3, within the observational uncertainties. However, somewhat unexpectedly, we derive a low ortho/para ratio of $2.35 \pm 0.35$, corresponding to a spin temperature of $\sim$27~K, towards Sagittarius~B2(M) at velocities of the expanding molecular ring. Water molecules in this region appear to have formed with, or relaxed to, an ortho/para ratio close to the value corresponding to the local temperature of the gas and dust.

D. C. Lis et al., Herschel /HIFI discovery of interstellar chloronium (H2Cl+) (CHESS, HEXOS, HOP)

  1007.1461            CHESS, HEXOS, HOP

D. C. Lis, J. C. Pearson, D. A. Neufeld, P. Schilke, H. S. P. Muller, H. Gupta, T. A. Bell, C. Comito, T. G. Phillips, E. A. Bergin, C. Ceccarelli, P. F. Goldsmith, G. A. Blake, A. Bacmann, A. Baudry, M. Benedettini, A. Benz, J. Black, A. Boogert, S. Bottinelli, S. Cabrit, P. Caselli, A. Castets, E. Caux, J. Cernicharo, C. Codella, A. Coutens, N. Crimier, N. R. Crockett, F. Daniel, K. Demyk, C. Dominic, M.-L. Dubernet, M. Emprechtinger, P. Encrenaz, E. Falgarone, A. Fuente, M. Gerin, T. F. Giesen, J. R. Goicoechea, F. Helmich, P. Hennebelle, Th. Henning, E. Herbst, P. Hily-Blant, A. Hjalmarson, D. Hollenbach, T. Jack, C. Joblin, D. Johnstone, C. Kahane, M. Kama, M. Kaufman, A. Klotz, W. D. Langer, B. Larsson, J. Le Bourlot, B. Lefloch, F. Le Petit, D. Li, R. Liseau, S. D. Lord, A. Lorenzani, S. Maret, P. G. Martin, G. J. Melnick, K. M. Menten, P. Morris, J. A. Murphy, Z. Nagy, B. Nisini, V. Ossenkopf, S. Pacheco, L. Pagani, B. Parise, M. Perault, R. Plume, S.-L. Qin, E. Roueff, M. Salez, A. Sandqvist, P. Saraceno, S. Schlemmer, K. Schuster, R. Snell, J. Stutzki, A. Tielens, N. Trappe, F. F. S. van der Tak, M. H. D. van der Wiel, E. van Dishoeck, C. Vastel, S. Viti, V. Wakelam, A. Walters, S. Wang, F. Wyrowski, H. W. Yorke, S. Yu, J. Zmuidzinas, Y. Delorme, J.-P. Desbat, R. Gusten, J.-M. Krieg, and B. Delforge

We report the first detection of chloronium, H$_2$Cl$^+$, in the interstellar medium, using the HIFI instrument aboard the \emph{Herschel} Space Observatory. The $2_{12}-1_{01}$ lines of ortho-H$_2^{35}$Cl$^+$ and ortho-H$_2^{37}$Cl$^+$ are detected in absorption towards NGC~6334I, and the $1_{11}-0_{00}$ transition of para-H$_2^{35}$Cl$^+$ is detected in absorption towards NGC~6334I and Sgr~B2(S). The H$_2$Cl$^+$ column densities are compared to those of the chemically-related species HCl. The derived HCl/H$_2$Cl$^+$ column density ratios, $\sim$1--10, are within the range predicted by models of diffuse and dense Photon Dominated Regions (PDRs). However, the observed H$_2$Cl$^+$ column densities, in excess of $10^{13}$~cm$^{-2}$, are significantly higher than the model predictions. Our observations demonstrate the outstanding spectroscopic capabilities of HIFI for detecting new interstellar molecules and providing key constraints for astrochemical models.

E. Falgarone et al., Strong CH+ J=1-0 emission and absorption in DR21 (WADI)

  1007.1420            WADI

E. Falgarone, V. Ossenkopf, M. Gerin, P. Lesaffre, B. Godard, J. Pearson, S. Cabrit, Ch. Joblin, A. O. Benz, F. Boulanger, A. Fuente, R. Gusten, A. Harris, T. Klein, C. Kramer, S. Lord, P. Martin, J. Martin-Pintado, D. Neufeld, T. G. Phillips, M. Rollig, R. Simon, J. Stutzki, F. van der Tak, D. Teyssier, H. Yorke, N. Erickson, M. Fich, W. Jellema, A. Marston, C. Risacher, M. Salez, F. Schmulling

We report the first detection of the ground-state rotational transition of the methylidyne cation CH+ towards the massive star-forming region DR21 with the HIFI instrument onboard the Herschel satellite. The line profile exhibits a broad emission line, in addition to two deep and broad absorption features associated with the DR21 molecular ridge and foreground gas. These observations allow us to determine a CH+ J=1-0 line frequency of 835137 +/- 3 MHz, in good agreement with a recent experimental determination. We estimate the CH+ column density to be a few 1e13 cm^-2 in the gas seen in emission, and > 1e14 cm^-2 in the components responsible for the absorption, which is indicative of a high line of sight average abundance [CH+]/[H] > 1.2x10^-8. We show that the CH+ column densities agree well with the predictions of state-of-the-art C-shock models in dense UV-illuminated gas for the emission line, and with those of turbulent dissipation models in diffuse gas for the absorption lines.

K. M. Menten et al., Herschel/HIFI deepens the circumstellar NH3 enigma (HIFISTARS)

  1007.1413            HIFISTARS

K. M. Menten, F. Wyrowski, J. Alcolea, E. De Beck, L. Decin, A. P. Marston, V. Bujarrabal, J. Cernicharo, C. Dominik, K. Justtanont, A. de Koter, G. Melnick, D. A. Neufeld, H. Olofsson, P. Planesas, M. Schmidt, F. L. Schoeier, R. Szczerba, D. Teyssier, L. B. F. M. Waters, K. Edwards, M. Olberg, T. G. Phillips, P. Morris, M. Salez, E. Caux

Circumstellar envelopes (CSEs) of a variety of evolved stars have been found to contain ammonia (NH3) in amounts that exceed predictions from conventional chemical models by many orders of magnitude. The observations reported here were performed in order to better constrain the NH3 abundance in the CSEs of four, quite diverse, oxygen-rich stars using the NH3 ortho J_K = 1_0 - 0_0 ground-state line. We used the Heterodyne Instrument for the Far Infrared aboard Herschel to observe the NH3 J_K = 1_0 - 0_0 transition near 572.5 GHz, simultaneously with the ortho-H2O J_Ka,Kc = 1_1,0 -1_0,1 transition, toward VY CMa, OH 26.5+0.6, IRC+10420, and IK Tau. We conducted non-LTE radiative transfer modeling with the goal to derive the NH3 abundance in these objects' CSEs. For the latter two stars, Very Large Array imaging of NH3 radio-wavelength inversion lines were used to provide further constraints, particularly on the spatial extent of the NH3-emitting regions. Results. We find remarkably strong NH3 emission in all of our objects with the NH3 line intensities rivaling those obtained for the ground state H2O line. The NH3 abundances relative to H2 are very high and range from 2 x 10-7 to 3 x 10-6 for the objects we have studied. Our observations confirm and even deepen the circumstellar NH3 enigma. While our radiative transfer modeling does not yield satisfactory fits to the observed line profiles, it leads to abundance estimates that confirm the very high values found in earlier studies. New ways to tackle this mystery will include further Herschel observations of more NH3 lines and imaging with the Expanded Very Large Array.

P. Hartogh et al., Herschel/HIFI observations of Mars: first detection of O2 at submillimetre wavelengths and upper limits on HCl and H2O2 (HssO)

  1007.1301            HssO

P. Hartogh, C. Jarchow, E. Lellouch, M. de Val-Borro, M. Rengel, R. Moreno, A. S. Medvedev, H. Sagawa, B. M. Swinyard, T. Cavalié, D. C. Lis, M. I. B\u0142\u0119cka, M. Banaszkiewicz, D. Bockelée-Morvan, J. Crovisier, T. Encrenaz, M. Küppers, L.-M. Lara, S. Szutowicz, B. Vandenbussche, F. Bensch, E. A. Bergin, F. Billebaud, N. Biver, G. A. Blake, J. A. D. L. Blommaert, J. Cernicharo, L. Decin, P. Encrenaz, H. Feuchtgruber, T. Fulton, T. de Graauw, E. Jehin, M. Kidger, R. Lorente, D. A. Naylor, G. Portyankina, M. Sánchez-Portal, R. Schieder, S. Sidher, N. Thomas, E. Verdugo, C. Waelkens, N. Whyborn, D. Teyssier, F. Helmich, P. Roelfsema, J. Stutzki, H. G. LeDuc, J. A. Stern

We report on the initial analysis of Herschel/HIFI observations of hydrogen chloride (HCl), hydrogen peroxide (H_2O_2) and molecular oxygen (O_2) in the martian atmosphere performed on 13 and 16 April 2010 (L_s ~ 77{\deg}). We derived a constant volume mixing ratio of 1400 +/- 120 ppm for O_2 and determined upper limits of 200 ppt for HCl and 2 ppb for H_2O_2. Radiative transfer model calculations indicate that the vertical profile of O_2 may not be constant. Photochemical models find lowest values for H_2O_2 around L_s ~ 75{\deg} but overestimate the volume mixing ratio compared to our measurements.

P. Hartogh et al., First results on martian carbon monoxide from Herschel/HIFI observations (HssO)

  1007.1291            HssO

P. Hartogh, M. I. Blecka, C. Jarchow, H. Sagawa, E. Lellouch, M. de Val-Borro, M. Rengel, A. S. Medvedev, B. M. Swinyard, R. Moreno, T. Cavalié, D. C. Lis, M. Banaszkiewicz, D. Bockelée-Morvan, J. Crovisier, T. Encrenaz, M. Küppers, L.-M. Lara, S. Szutowicz, B. Vandenbussche, F. Bensch, E. A. Bergin, F. Billebaud, N. Biver, G. A. Blake, J. A. D. L. Blommaert, J. Cernicharo, L. Decin, P. Encrenaz, H. Feuchtgruber, T. Fulton, T. de Graauw, E. Jehin, M. Kidger, R. Lorente, D. A. Naylor, G. Portyankina, M. Sánchez-Portal, R. Schieder, S. Sidher, N. Thomas, E. Verdugo, C. Waelkens, A. Lorenzani, G. Tofani, E. Natale, J. Pearson, T. Klein, C. Leinz, R. Güsten, C. Kramer

We report on the initial analysis of Herschel/HIFI carbon monoxide observations of the martian atmosphere performed between 11 and 16 April 2010. We selected the (7-6) rotational transitions of the isotopes ^{13}CO and C^{18}O at 771 and 768 GHz respectively in order to retrieve the mean vertical profile of temperature and the mean volume mixing ratio of carbon monoxide. The derived temperature profile agrees within less than 5 K with general circulation model predictions up to an altitude of 45 km, however show about 12-15 K lower values at 60 km. The carbon monoxide mixing ratio was determined to be 980 \pm 150 ppm, in agreement with the 900 ppm derived from Herschel/SPIRE observations in November 2009.

P.Caselli et al., Water vapor toward starless cores: the Herschel view (WISH)

  1007.1248            WISH

P.Caselli, E.Keto, L. Pagani, Y. Aikawa, U.A. Yildiz, F.F.S. van der Tak, M. Tafalla, E.A. Bergin, B. Nisini, C. Codella, E.F. van Dishoeck, R. Bachiller, A. Baudry, M. Benedettini, A.O. Benz, P. Bjerkeli, G.A. Blake, S. Bontemps, J. Braine, S. Bruderer, J. Cernicharo, F. Daniel, A.M. di Giorgio, C. Dominik, S.D. Doty, P. Encrenaz, M. Fich, A. Fuente, T. Gaier, T. Giannini, J.R. Goicoechea, Th. de Graauw, F. Helmich, G.J. Herczeg, F. Herpin, M.R. Hogerheijde, B. Jackson, T. Jacq, H. Javadi, D. Johnstone, J.K. Jorgensen, D. Kester, L.E. Kristensen, W. Laauwen, B. Larsson, D. Lis, R. Liseau, W. Luinge, M. Marseille, C. McCoey, A. Megej, G. Melnick, D. Neufeld, M. Olberg, B. Parise, J.C. Pearson, R. Plume, C. Risacher, J. Santiago-Garcia, P. Saraceno, R. Shipman, P. Siegel, T.A. van Kempen, R. Visser, S.F. Wampfler, F. Wyrowski

SWAS and Odin provided stringent upper limits on the gas phase water abundance of dark clouds (x(H2O) < 7x10^-9). We investigate the chemistry of water vapor in starless cores beyond the previous upper limits using the highly improved angular resolution and sensitivity of Herschel and measure the abundance of water vapor during evolutionary stages just preceding star formation. High spectral resolution observations of the fundamental ortho water (o-H2O) transition (557 GHz) were carried out with Herschel HIFI toward two starless cores: B68, a Bok globule, and L1544, a prestellar core embedded in the Taurus molecular cloud complex. The rms in the brightness temperature measured for the B68 and L1544 spectra is 2.0 and 2.2 mK, respectively, in a velocity bin of 0.59 km s^-1. The continuum level is 3.5+/-0.2 mK in B68 and 11.4+/-0.4 mK in L1544. No significant feature is detected in B68 and the 3 sigma upper limit is consistent with a column density of o-H2O N(o-H2O) < 2.5x10^13 cm^-2, or a fractional abundance x(o-H2O) < 1.3x10^-9, more than an order of magnitude lower than the SWAS upper limit on this source. The L1544 spectrum shows an absorption feature at a 5 sigma level from which we obtain the first value of the o-H2O column density ever measured in dark clouds: N(o-H2O) = (8+/-4)x10^12 cm^-2. The corresponding fractional abundance is x(o-H2O) ~ 5x10^-9 at radii > 7000 AU and ~2x10^-10 toward the center. The radiative transfer analysis shows that this is consistent with a x(o-H2O) profile peaking at ~10^-8, 0.1 pc away from the core center, where both freeze-out and photodissociation are negligible. Herschel has provided the first measurement of water vapor in dark regions. Prestellar cores such as L1544 (with their high central densities, strong continuum, and large envelopes) are very promising tools to finally shed light on the solid/vapor balance of water in molecular clouds.

D. A. Neufeld et al., Discovery of water vapour in the carbon star V Cygni from observations with Herschel/HIFI (HIFISTARS)

  1007.1235            HIFISTARS

D. A. Neufeld, E. González-Alfonso, G. Melnick, M. Pu\u0142ecka, M. Schmidt, R. Szczerba, V. Bujarrabal, J. Alcolea, J. Cernicharo, L. Decin, C. Dominik, K. Justtanont, A. de Koter, A. P. Marston, K. Menten, H. Olofsson, P. Planesas, F. L. Schöier, D. Teyssier, L. B. F. M. Waters, K. Edwards, C. McCoey, R. Shipman, W. Jellema, T. de Graauw, V. Ossenkopf, R. Schieder, S. Philipp

We report the discovery of water vapour toward the carbon star V Cygni. We have used Herschel's HIFI instrument, in dual beam switch mode, to observe the 1(11) - 0(00) para-water transition at 1113.3430 GHz in the upper sideband of the Band 4b receiver. The observed spectral line profile is nearly parabolic, but with a slight asymmetry associated with blueshifted absorption, and the integrated antenna temperature is 1.69 \pm 0.17 K km/s. This detection of thermal water vapour emission, carried out as part of a small survey of water in carbon-rich stars, is only the second such detection toward a carbon-rich AGB star, the first having been obtained by the Submillimeter Wave Astronomy Satellite toward IRC+10216. For an assumed ortho-to-para ratio of 3 for water, the observed line intensity implies a water outflow rate ~ (3 - 6) E-5 Earth masses per year and a water abundance relative to H2 of ~ (2-5) E-6. This value is a factor of at least 1E+4 larger than the expected photospheric abundance in a carbon-rich environment, and - as in IRC+10216 - raises the intriguing possibility that the observed water is produced by the vapourisation of orbiting comets or dwarf planets. However, observations of the single line observed to date do not permit us to place strong constraints upon the spatial distribution or origin of the observed water, but future observations of additional transitions will allow us to determine the inner radius of the H2O-emitting zone, and the H2O ortho-to-para ratio, and thereby to place important constraints upon the origin of the observed water emission.

A. Weiss et al., HIFI spectroscopy of low-level water transitions in M82 (HEXGAL)

  1007.1167            HEXGAL

A. Weiss, M.A. Requena-Torres, R. Guesten, S. Garcia-Burillo, A.I. Harris, F.P. Israel, T. Klein, C. Kramer, S. Lord, J. Martin-Pintado, M. Roellig, J. Stutzki, R. Szczerba, P.P. van der Werf, S. Philipp-May, H. Yorke, M. Akyilmaz, C. Gal, R. Higgins, A. Marston, J. Roberts, F. Schloeder, M. Schultz, D. Teyssier, N. Whyborn, H. J. Wunsch

We present observations of the rotational ortho-water ground transition, the two lowest para-water transitions, and the ground transition of ionised ortho-water in the archetypal starburst galaxy M82, performed with the HIFI instrument on the Herschel Space Observatory. These observations are the first detections of the para-H2O(111-000) (1113\,GHz) and ortho-H2O+(111-000) (1115\,GHz) lines in an extragalactic source. All three water lines show different spectral line profiles, underlining the need for high spectral resolution in interpreting line formation processes. Using the line shape of the para-H2O(111-000) and ortho-H2O+(111-000) absorption profile in conjunction with high spatial resolution CO observations, we show that the (ionised) water absorption arises from a ~2000 pc^2 region within the HIFI beam located about ~50 pc east of the dynamical centre of the galaxy. This region does not coincide with any of the known line emission peaks that have been identified in other molecular tracers, with the exception of HCO. Our data suggest that water and ionised water within this region have high (up to 75%) area-covering factors of the underlying continuum. This indicates that water is not associated with small, dense cores within the ISM of M82 but arises from a more widespread diffuse gas component.

L. Decin et al., Water content and wind acceleration in the envelope around the oxygen-rich AGB star IK Tau as seen by Herschel/HIFI (HIFISTARS)

  1007.1102            HIFISTARS

L. Decin, K. Justtanont, E. De Beck, R. Lombaert, A. de Koter, L.B.F.M. Waters, the HIFISTARS team

During their asymptotic giant branch, evolution low-mass stars lose a significant fraction of their mass through an intense wind, enriching the interstellar medium with products of nucleosynthesis. We observed the nearby oxygen-rich asymptotic giant branch star IK Tau using the high-resolution HIFI spectrometer onboard Herschel. We report on the first detection of H_2^{16}O and the rarer isotopologues H_2^{17}O and H_2^{18}O in both the ortho and para states. We deduce a total water content (relative to molecular hydrogen) of 6.6x10^{-5}, and an ortho-to-para ratio of 3:1. These results are consistent with the formation of H_2O in thermodynamical chemical equilibrium at photospheric temperatures, and does not require pulsationally induced non-equilibrium chemistry, vaporization of icy bodies or grain surface reactions. High-excitation lines of 12CO, 13CO, 28SiO, 29SiO, 30SiO, HCN, and SO have also been detected. From the observed line widths, the acceleration region in the inner wind zone can be characterized, and we show that the wind acceleration is slower than hitherto anticipated.

D. A. Neufeld et al., Herschel/HIFI obs. of interstellar OH+ and H2O+ towards W49N: a probe of diffuse clouds with a small molecular fraction (PRISMAS)

  1007.0987            PRISMAS

D. A. Neufeld, J. R. Goicoechea, P. Sonnentrucker, J. H. Black, J. Pearson, S. Yu, T. G. Phillips, D. C. Lis, M. De Luca, E. Herbst, P. Rimmer, M. Gerin, T. A. Bell, F. Boulanger, J. Cernicharo, A. Coutens, E. Dartois, M. Kazmierczak, P. Encrenaz, E. Falgarone, T. R. Geballe, T. Giesen, B. Godard, P. F. Goldsmith, C. Gry, H. Gupta, P. Hennebelle, P. Hily-Blant, C. Joblin, R. Ko\los, J. Kre\lowski, J. Mart\in-Pintado, K. M. Menten, R. Monje, B. Mookerjea, M. Perault, C. Persson, R. Plume, M. Salez, S. Schlemmer, M. Schmidt, J. Stutzki, D. Teyssier, C. Vastel, A. Cros, K. Klein, A. Lorenzani, S. Philipp, L. A. Samoska, R. Shipman, A. G. G. M. Tielens, R. Szczerba, J. Zmuidzinas

We report the detection of absorption by interstellar hydroxyl cations and water cations, along the sight-line to the bright continuum source W49N. We have used Herschel's HIFI instrument, in dual beam switch mode, to observe the 972 GHz N = 1 - 0 transition of OH+ and the 1115 GHz 1(11) - 0(00) transition of ortho-H2O+. The resultant spectra show absorption by ortho-H2O+, and strong absorption by OH+, in foreground material at velocities in the range 0 to 70 km/s with respect to the local standard of rest. The inferred OH+/H2O+ abundance ratio ranges from ~ 3 to ~ 15, implying that the observed OH+ arises in clouds of small molecular fraction, in the 2 - 8% range. This conclusion is confirmed by the distribution of OH+ and H2O+ in Doppler velocity space, which is similar to that of atomic hydrogen, as observed by means of 21 cm absorption measurements, and dissimilar from that typical of other molecular tracers. The observed OH+/H abundance ratio of a few E-8 suggests a cosmic ray ionization rate for atomic hydrogen of (0.6 - 2.4) E-16 s-1, in good agreement with estimates inferred previously for diffuse clouds in the Galactic disk from observations of interstellar H3+ and other species.

M. Harwit et al., Polarisation Observations of VY Canis Majoris Water Vapour 5{32}-4{41} 620.701 GHz Maser Emission with HIFI

  1007.0905           

Martin Harwit, Martin Houde, Paule Sonnentrucker, J. Cernicharo, L. Decin, C. Henkel, R. D. Higgins, W. Jellema, A. Kraus, Carolyn McCoey, G. J. Melnick, K. M. Menten, C. Risacher, D. Teyssier, J. E. Vaillancourt, J. Alcolea, V. Bujarrabal, C. Dominik, K. Justtanont, A. de Koter, A. P. Marston, H. Olofsson, P. Planesas, M. Schmidt, F. L. Schöier, R. Szczerba, L. B. F. M. Waters

CONTEXT: Water vapour maser emission from evolved oxygen-rich stars remains poorly understood. Additional observations, including polarisation studies and simultaneous observation of different maser transitions may ultimately lead to greater insight. AIMS: We have aimed to elucidate the nature and structure of the VY CMa water vapour masers in part by observationally testing a theoretical prediction of the relative strengths of the 620.701 GHz and the 22.235 GHz maser components of ortho water vapour. METHODS: In its high-resolution mode (HRS) the Herschel Heterodyne Instrument for the Infrared (HIFI) offers a frequency resolution of 0.125 MHz, corresponding to a line-of-sight velocity of 0.06 km/s, which we employed to obtain the strength and linear polarisation of maser spikes in the spectrum of VY CMa at 620.701 GHz. Simultaneous ground based observations of the 22.235 GHz maser with the Max-Planck-Institut f\"ur Radioastronomie 100-meter telescope at Effelsberg, provided a ratio of 620.701 GHz to 22.235 GHz emission. RESULTS:We report the first astronomical detection to date of water vapour maser emission at 620.701 GHz. In VY CMa both the 620.701 and the 22.235 GHz polarisation are weak. At 620.701 GHz the maser peaks are superposed on what appears to be a broad emission component, jointly ejected asymmetrically from the star. We observed the 620.701 GHz emission at two epochs 21 days apart, both to measure the potential direction of linearly polarised maser components and to obtain a measure of the longevity of these components. Although we do not detect significant polarisation levels in the core of the line, they rise up to approximately 12% in its wings.

P. Schilke et al., Herschel observations of ortho- and para-oxidaniumyl (H2O+) in spiral arm clouds toward Sgr B2(M) (HEXOS)

  1007.0670            HEXOS

P. Schilke, C. Comito, H.S.P. Mueller, E.A. Bergin, E. Herbst, D.C. Lis, D.A. Neufeld, T.G. Phillips, T.A. Bell, G.A. Blake, S. Cabrit, E. Caux, C. Ceccarelli, J. Cernicharo, N.R. Crockett, F. Daniel, M.-L. Dubernet, M. Emprechtinger, P. Encrenaz, M.~Gerin, T.F. Giesen, J.R. Goicoechea, P.F. Goldsmith, H. Gupta, C. Joblin, D. Johnstone, W.D. Langer, W.B. Latter, S.D. Lord, S. Maret, P. G. Martin, G.J. Melnick, K.M. Menten, P. Morris, J.A. Murphy, V. Ossenkopf, L. Pagani, J.C. Pearson, M. Perault, R. Plume, S.-L. Qin, M. Salez, S. Schlemmer, J. Stutzki, N. Trappe, F.F.S. van der Tak, C. Vastel, S. Wang, H.W. Yorke, S. Yu, N. Erickson, F.W. Maiwald, J. Kooi, A. Karpov, J. Zmuidzinas, A. Boogert, R. Schieder, P. Zaal

H2O+ has been observed in its ortho- and para- states toward the massive star forming core Sgr B2(M), located close to the Galactic center. The observations show absorption in all spiral arm clouds between the Sun and Sgr B2. The average o/p ratio of H2O+ in most velocity intervals is 4.8, which corresponds to a nuclear spin temperature of 21 K. The relationship of this spin temperature to the formation temperature and current physical temperature of the gas hosting H2O+ is discussed, but no firm conclusion is reached. In the velocity interval 0 to 60 km/s, an ortho/para ratio of below unity is found, but if this is due to an artifact of contamination by other species or real is not clear.

B. Mookerjea et al., Excitation and Abundance of C3 in star forming cores:Herschel/HIFI observations of the sight-lines to W31C and W49N (PRISMAS)

  1007.0649            PRISMAS

B. Mookerjea, T. Giesen, J. Stutzki, J. Cernicharo, J. R. Goicoechea, M. De Luca, T. A. Bell, H. Gupta, M. Gerin, C. M. Persson, P. Sonnentrucker, Z. Makai, J. Black, F. Boulanger, A. Coutens, E. Dartois, P. Encrenaz, E. Falgarone, T. Geballe, B. Godard, P. F. Goldsmith, C. Gry, P. Hennebelle E. Herbst, P. Hily-Blant, C. Joblin, M. Ka\u017amierczak, R. Ko\los, J. Kre\lowski, D. C. Lis, J. Martin-Pintado, K. M. Menten, R. Monje, J. C. Pearson, M. Perault, T. G. Phillips, R. Plume, M. Salez, S. Schlemmer, M. Schmidt, D. Teyssier, C. Vastel, S. Yu, P. Dieleman, R. GĂĽsten, C. E. Honingh, P. Morris, P. Roelfsema, R. Schieder, A. G. G. M. Tielens, J. Zmuidzinas

We present spectrally resolved observations of triatomic carbon (C3) in several ro-vibrational transitions between the vibrational ground state and the low-energy nu2 bending mode at frequencies between 1654-1897 GHz along the sight-lines to the submillimeter continuum sources W31C and W49N, using Herschel's HIFI instrument. We detect C3 in absorption arising from the warm envelope surrounding the hot core, as indicated by the velocity peak position and shape of the line profile. The sensitivity does not allow to detect C3 absorption due to diffuse foreground clouds. From the column densities of the rotational levels in the vibrational ground state probed by the absorption we derive a rotation temperature (T_rot) of ~50--70 K, which is a good measure of the kinetic temperature of the absorbing gas, as radiative transitions within the vibrational ground state are forbidden. It is also in good agreement with the dust temperatures for W31C and W49N. Applying the partition function correction based on the derived T_rot, we get column densities N(C3) ~7-9x10^{14} cm^{-2} and abundance x(C3)~10^{-8} with respect to H2. For W31C, using a radiative transfer model including far-infrared pumping by the dust continuum and a temperature gradient within the source along the line of sight we find that a model with x(C3)=10^{-8}, T_kin=30-50 K, N(C3)=1.5 10^{15} cm^{-2} fits the observations reasonably well and provides parameters in very good agreement with the simple excitation analysis.

M. de Val-Borro et al., Water production in comet 81P/Wild 2 as determined by Herschel/HIFI (HssO)

  1007.0149            HssO

M. de Val-Borro, P. Hartogh, J. Crovisier, D. Bockelée-Morvan, N. Biver, D. C. Lis, R. Moreno, C. Jarchow, M. Rengel, S. Szutowicz, M. Banaszkiewicz, F. Bensch, M. I. B\u0142\u0119cka, M. Emprechtinger, T. Encrenaz, E. Jehin, M. Küppers, L.-M. Lara, E. Lellouch, B. M. Swinyard, B. Vandenbussche, E. A. Bergin, G. A. Blake, J. A. D. L. Blommaert, J. Cernicharo, L. Decin, P. Encrenaz, T. de Graauw, D. Hutsemékers, M. Kidger, J. Manfroid, A. S. Medvedev, D. A. Naylor, R. Schieder, D. Stam, N. Thomas, C. Waelkens, R. Szczerba, P. Saraceno, A. M. Di Giorgio, S. Philipp, T. Klein, V. Ossenkopf, P. Zaal, R. Shipman

The high spectral resolution and sensitivity of Herschel/HIFI allows for the detection of multiple rotational water lines and accurate determinations of water production rates in comets. In this letter we present HIFI observations of the fundamental 110-101 (557 GHz) ortho and 111-000 (1113 GHz) para rotational transitions of water in comet 81P/Wild 2 acquired in February 2010. We mapped the extent of the water line emission with five point scans. Line profiles are computed using excitation models which include excitation by collisions with electrons and neutrals and solar infrared radiation. We derive a mean water production rate of $1.0 \times 10^{28}$ molecules s$^{-1}$ at a heliocentric distance of 1.61 AU about 20 days before perihelion, in agreement with production rates measured from the ground using observations of the 18-cm OH lines. Furthermore, we constrain the electron density profile and gas kinetic temperature, and estimate the coma expansion velocity by fitting the water line shapes.

A.F. Loenen et al., Excitation of the molecular gas in the nuclear region of M82 (HEXGAL)

  1006.5006            HEXGAL

A.F. Loenen, P.P. van der Werf, R. Güsten, R. Meijerink, F.P Israel, M.A. Requena-Torres, S. García-Burillo, A.I. Harris, T. Klein, C. Kramer, S. Lord, J. Martín-Pintado, M. Röllig, J. Stutzki, R. Szczerba, A. Weiß, S. Philipp-May, H. Yorke, E. Caux, B. Delforge, F. Helmich, A. Lorenzani, P. Morris, T.G. Philips, C. Risacher, A.G.G.M. Tielens

We present high resolution HIFI spectroscopy of the nucleus of the archetypical starburst galaxy M82. Six 12CO lines, 2 13CO lines and 4 fine-structure lines are detected. Besides showing the effects of the overall velocity structure of the nuclear region, the line profiles also indicate the presence of multiple components with different optical depths, temperatures and densities in the observing beam. The data have been interpreted using a grid of PDR models. It is found that the majority of the molecular gas is in low density (n=10^3.5 cm^-3) clouds, with column densities of N_H=10^21.5 cm^-2 and a relatively low UV radiation field (GO = 10^2). The remaining gas is predominantly found in clouds with higher densities (n=10^5 cm^-3) and radiation fields (GO = 10^2.75), but somewhat lower column densities (N_H=10^21.2 cm^-2). The highest J CO lines are dominated by a small (1% relative surface filling) component, with an even higher density (n=10^6 cm^-3) and UV field (GO = 10^3.25). These results show the strength of multi-component modeling for the interpretation of the integrated properties of galaxies.

C. Codella et al., The CHESS chemical Herschel surveys of star forming regions: Peering into the protostellar shock L1157-B1. I. Shock chemical ... (CHESS)

  1006.1864            CHESS

C. Codella, B. Lefloch, C. Ceccarelli, CHESS Team, HIFI Team

We present the first results of the unbiased survey of the L1157-B1 bow shock, obtained with HIFI in the framework of the key program Chemical Herschel surveys of star forming regions (CHESS). The L1157 outflow is driven by a low-mass Class 0 protostar and is considered the prototype of the so-called chemically active outflows. The bright blue-shifted bow shock B1 is the ideal laboratory for studying the link between the hot (around 1000-2000 K) component traced by H2 IR-emission and the cold (around 10-20 K) swept-up material. The main aim is to trace the warm gas chemically enriched by the passage of a shock and to infer the excitation conditions in L1157-B1. A total of 27 lines are identified in the 555-636 GHz region, down to an average 3 sigma level of 30 mK. The emission is dominated by CO(5-4) and H2O(110-101) transitions, as discussed by Lefloch et al. (2010). Here we report on the identification of lines from NH3, H2CO, CH3OH, CS, HCN, and HCO+. The comparison between the profiles produced by molecules released from dust mantles (NH3, H2CO, CH3OH) and that of H2O is consistent with a scenario in which water is also formed in the gas-phase in high-temperature regions where sputtering or grain-grain collisions are not efficient. The high excitation range of the observed tracers allows us to infer, for the first time for these species, the existence of a warm (> 200 K) gas component coexisting in the B1 bow structure with the cold and hot gas detected from ground.

B. Lefloch et al., CHESS, Chemical Herschel surveys of star forming regions:Peering into the protostellar shock L1157-B1 (CHESS)

  1006.1305            CHESS

B. Lefloch, S. Cabrit, C. Codella, G. Melnick, J. Cernicharo, E. Caux, M. Benedettini, A. Boogert, P. Caselli, C. Ceccarelli, F. Gueth, P. Hily-Blant, A. Lorenzani, D. Neufeld, B. Nisini, S. Pacheco, L. Pagani, J.R. Pardo, B. Parise, M. Salez, K. Schuster, S. Viti, A. Bacmann, A. Baudry, T. Bell, E.A. Bergin, G. Blake, S. Bottinelli, A. Castets, C. Comito, A. Coutens, N. Crimier, C. Dominik, K. Demyk, P. Encrenaz, E. Falgarone, A. Fuente, M. Gerin, P. Goldsmith, F. Helmich, P. Hennebelle, T. Henning, E. Herbst, T. Jacq, C. Kahane, M. Kama, A. Klotz, W. Langer, D. Lis, S. Lord, S. Maret, J. Pearson, T. Phillips, P. Saraceno, P. Schilke, A.G.G.M. Tielens, F. van der Tak, M. van der Wiel, C. Vastel, V. Wakelam, A. Walters, F. Wyrowski, H. Yorke, R. Bachiller, C. Borys, G. De Lange, Y. Delorme, C. Kramer, B. Larsson, R. Lai, F.W. Maiwald, J. Martin-Pintado, I. Mehdi, V. Ossenkopf, P. Siegel, J. Stutzki, J.H. Wunsch

The outflow driven by the low-mass class 0 protostar L1157 is the prototype of the so-called chemically active outflows. The bright bowshock B1 in the southern outflow lobe is a privileged testbed of magneto-hydrodynamical (MHD) shock models, for which dynamical and chemical processes are strongly interdependent. We present the first results of the unbiased spectral survey of the L1157-B1 bowshock, obtained in the framework of the key program "Chemical Herschel Surveys of Star Forming Regions" (CHESS). The main aim is to trace the warm and chemically enriched gas and to infer the excitation conditions in the shock region. The CO 5-4 and H2O lines have been detected at high-spectral resolution in the unbiased spectral survey of the HIFI-Band 1b spectral window (555-636 GHz), presented by Codella et al. in this volume. Complementary ground-based observations in the submm window help establish the origin of the emission detected in the main-beam of HIFI, and the physical conditions in the shock.}{Both lines exhibit broad wings, which extend to velocities much higher than reported up to now. We find that the molecular emission arises from two regions with distinct physical conditions: an extended, warm (100K), dense (3e5 cm-3) component at low-velocity, which dominates the water line flux in Band~1; a secondary component in a small region of B1 (a few arcsec) associated with high-velocity, hot (> 400 K) gas of moderate density ((1.0-3.0)e4 cm-3), which appears to dominate the flux of the water line at 179mu observed with PACS. The water abundance is enhanced by two orders of magnitude between the low- and the high-velocity component, from 8e-7 up to 8e-5. The properties of the high-velocity component agree well with the predictions of steady-state C-shock models.

M. Gerin et al., Interstellar OH+, H2O+ and H3O+ along the sight-line to G10.6-0.4 (PRISMAS)

  1005.5653            PRISMAS

Maryvonne Gerin (LERMA), M. De Luca (LERMA), John Black (oso), Eric Herbst (OHIO STATE UNIVERSITY), Javier R.Goicoechea (CAB-INTA, CSIS), Edith Falgarone (LERMA), Benjamin Godard (LERMA), John C. Pearson (JPL), Dariucz C. Lis (CSO), Thomas G. Phillips (CSO), Thomas A. Bell (CSO), Paule Sonnentrucker, Francois Boulanger (IAS), Jose Cernicharo (CAB-INTA, CSIS), Audrey Coutens (CESR), Emmanuel Dartois (IAS), Pierre Encrenaz (LERMA), Thomas Giesen, Paul F. Goldsmith (JPL), Harshal Gupta (JPL), Cecile Gry (LAM), Patrick Hennebelle (LERMA), Pierre Hily-Blant (LAOG), Christine Joblin (CESR), Maja Kazmierczak, Robert Kolos, Jacek Krelowski, Jesus Martin-Pintado (IEM), Raquel Monje (CSO), Bhaswati Mookerjea, Michel PĂ©rault (LERMA), Carina Persson (oso), Rene Plume, Paul B. Rimmer (OHIO STATE UNIVERSITY), Morvan Salez (LERMA), Mirisloaw Schmidt, David Teyssier (LERMA), Charlotte Vastel (CESR), Shan Shan Yu (JPL), Alessandra Contursi (MPE), Karl Menten (MpIfR), Thomas Geballe, Stephan Schlemmer, Russ Shipman (SRON), Alexander G.G.M. Tielens, Sabine Philipp-May (MpIfR), Alain Cros (LP3), Jonas Zmuidzinas (CSO), L. A Samoska (JPL), K. Klein, D.A. Neufeld, A. Lorenzani, JĂĽrgen Stutzki

We report the detection of absorption lines by the reactive ions OH+, H2O+ and H3O+ along the line of sight to the submillimeter continuum source G10.6$-$0.4 (W31C). We used the Herschel HIFI instrument in dual beam switch mode to observe the ground state rotational transitions of OH+ at 971 GHz, H2O+ at 1115 and 607 GHz, and H3O+ at 984 GHz. The resultant spectra show deep absorption over a broad velocity range that originates in the interstellar matter along the line of sight to G10.6$-$0.4 as well as in the molecular gas directly associated with that source. The OH+ spectrum reaches saturation over most velocities corresponding to the foreground gas, while the opacity of the H2O+ lines remains lower than 1 in the same velocity range, and the H3O+ line shows only weak absorption. For LSR velocities between 7 and 50 kms$^{-1}$ we estimate total column densities of $N$(OH+) $> 2.5 \times 10^{14}$ cm$^{-2}$, $N$(H2O+) $\sim 6 \times 10^{13}$ cm$^{-2}$ and $N$(H3O+) $\sim 4.0 \times 10^{13}$ cm$^{-2}$. These detections confirm the role of O$^+$ and OH$^+$ in initiating the oxygen chemistry in diffuse molecular gas and strengthen our understanding of the gas phase production of water. The high ratio of the OH+ by the H2O+ column density implies that these species predominantly trace low-density gas with a small fraction of hydrogen in molecular form.

P. Hartogh et al., HIFI Observations of Water in the Atmosphere of Comet C/2008 Q3 (Garradd) (HssO)

  1005.2969            HssO

P. Hartogh, J. Crovisier, M. de Val-Borro, D. Bockelée-Morvan, N. Biver, D. C. Lis, R. Moreno, C. Jarchow, M. Rengel, M. Emprechtinger, S. Szutowicz, M. Banaszkiewicz, F. Bensch, M. I. Blecka, T. Cavalié, T. Encrenaz, E. Jehin, M. Küppers, L.-M. Lara, E. Lellouch, B. M. Swinyard, B. Vandenbussche, E. A. Bergin, G. A. Blake, J. A. D. L. Blommaert, J. Cernicharo, L. Decin, P. Encrenaz, T. de Graauw, D. Hutsemekers, M. Kidger, J. Manfroid, A. S. Medvedev, D. A. Naylor, R. Schieder, N. Thomas, C. Waelkens, P. R. Roelfsema, P. Dieleman, R. Guesten, T. Klein, C. Kasemann, M. Caris, M. Olberg, A. O. Benz

High-resolution far-infrared and sub-millimetre spectroscopy of water lines is an important tool to understand the physical and chemical properties of cometary atmospheres. We present observations of several rotational ortho- and para-water transitions in comet C/2008 Q3 (Garradd) performed with HIFI on Herschel. These observations have provided the first detection of the 2_{12}-1_{01} (1669 GHz) ortho and 1_{11}-0_{00} (1113 GHz) para transitions of water in a cometary spectrum. In addition, the ground-state transition 1_{10}-1_{01} at 557 GHz is detected and mapped. By detecting several water lines quasi-simultaneously and mapping their emission we can constrain the excitation parameters in the coma. Synthetic line profiles are computed using excitation models which include excitation by collisions, solar infrared radiation, and radiation trapping. We obtain the gas kinetic temperature, constrain the electron density profile, and estimate the coma expansion velocity by analyzing the map and line shapes. We derive water production rates of 1.7-2.8 x 10^{28} s^{-1} over the range r_h = 1.83-1.85 AU.

F.F.S. van der Tak et al., Water abundance variations around high-mass protostars: Herschel-HIFI observations of the DR21 region (WISH)

  1005.2903            WISH

F.F.S. van der Tak, M.G. Marseille, F. Herpin, F. Wyrowski, A. Baudry, S. Bontemps, J. Braine, S. Doty, W. Frieswijk, G. Melnick, R. Shipman, E.F. van Dishoeck, A.O. Benz, P. Caselli, M. Hogerheijde, D. Johnstone, R. Liseau, R. Bachiller, M. Benedettini, E. Bergin, P. Bjerkeli, G. Blake, S. Bruderer, J. Cernicharo, C. Codella, F. Daniel, A.M. di Giorgio, C. Dominik, P. Encrenaz, M. Fich, A. Fuente, T. Giannini, J. Goicoechea, Th. de Graauw, F. Helmich, G. Herczeg, J. Jřrgensen, L. Kristensen, B. Larsson, D. Lis, C. McCoey, D. Neufeld, B. Nisini, M. Olberg, B. Parise, J. Pearson, R. Plume, C. Risacher, J. Santiago, P. Saraceno, M. Tafalla, T. van Kempen, R. Visser, S. Wampfler, U.A. Yildiz, L. Ravera, P. Roelfsema, O. Siebertz, and D. Teyssier

Water is a key molecule in the star formation process, but its spatial distribution in star-forming regions is not well known. We study the distribution of dust continuum and H2O and 13CO line emission in DR21, a luminous star-forming region with a powerful outflow and a compact HII region. Herschel-HIFI spectra near 1100 GHz show narrow 13CO 10-9 emission and H2O 1(11)-0(00) absorption from the dense core and broad emission from the outflow in both lines. The H2O line also shows absorption by a foreground cloud known from ground-based observations of low-J CO lines. The dust continuum emission is extended over 36" FWHM, while the 13CO and H2O lines are confined to ~24" or less. The foreground absorption appears to peak further North than the other components. Radiative transfer models indicate very low abundances of ~2e-10 for H2O and ~8e-7 for 13CO in the dense core, and higher H2O abundances of ~4e-9 in the foreground cloud and ~7e-7 in the outflow. The high H2O abundance in the warm outflow is probably due to the evaporation of water-rich icy grain mantles, while the H2O abundance is kept down by freeze-out in the dense core and by photodissociation in the foreground cloud.

J. Cernicharo et al., The 35Cl/37Cl isotopic ratio in dense molecular clouds: HIFI observations of hydrogen chloride towards W3A (HIFI-PV1)

  1005.2729            (HIFI-PV1)

J. Cernicharo, J.R. Goicoechea, F. Daniel, M. Agundez, E. Caux, T. de Graauw, A. De Jonge, D. Kester, H.G. Leduc, E. Steinmetz, J. Stutzki, J.S. Ward

We report on the detection with the HIFI instrument on board the Herschel satellite of the two hydrogen chloride isotopologues, H35Cl and H37Cl, towards the massive star-forming region W3A. The J=1-0 line of both species was observed with receiver 1b of the HIFI instrument at 625.9 and 624.9 GHz. The different hyperfine components were resolved. The observations were modeled with a non-local, non-LTE radiative transfer model that includes hyperfine line overlap and radiative pumping by dust. Both effects are found to play an important role in the emerging intensity from the different hyperfine components. The inferred H35Cl column density (a few times 1e14 cm^-2), and fractional abundance relative to H nuclei (~7.5e^-10), supports an upper limit to the gas phase chlorine depletion of ~200. Our best-fit model estimate of the H35Cl/H37Cl abundance ratio is ~2.1+/-0.5, slightly lower, but still compatible with the solar isotopic abundance ratio (~3.1). Since both species were observed simultaneously, this is the first accurate estimation of the [35Cl]/[37Cl] isotopic ratio in molecular clouds. Our models indicate that even for large line opacities and possible hyperfine intensity anomalies, the H35Cl and H37Cl J=1-0 integrated line-intensity ratio provides a good estimate of the 35Cl/37Cl isotopic abundance ratio.

V. Ossenkopf et al., Detection of interstellar oxidaniumyl: abundant H2O+ towards the star-forming regions DR21, Sgr B2, and NGC6334 (WADI, HEXOS, CHESS)

  1005.2521            WADI, HEXOS, CHESS

V. Ossenkopf, H.S.P. Müller, D.C. Lis, P. Schilke, T.A. Bell, S. Bruderer, E. Bergin, C. Ceccarelli, C. Comito, J. Stutzki, A. Bacman, A. Baudry, A.O. Benz, M. Benedettini, O. Berne, G. Blake, A. Boogert, S. Bottinelli, F. Boulanger, S. Cabrit, P. Caselli, E. Caux, J. Cernicharo, C. Codella, A. Coutens, N. Crimier, N.R. Crockett, F. Daniel, K. Demyk, P. Dieleman, C. Dominik, M.L. Dubernet, M. Emprechtinger, P. Encrenaz, E. Falgarone, K. France, A. Fuente, M. Gerin, T.F. Giesen, A.M. di Giorgio, J.R. Goicoechea, P.F. Goldsmith, R. Güsten, A. Harris, F. Helmich, E. Herbst, P. Hily-Blant, K. Jacobs, T. Jacq, Ch. Joblin, D. Johnstone, C. Kahane, M. Kama, T. Klein, A. Klotz, C. Kramer, W. Langer, B. Lefloch, C. Leinz, A. Lorenzani, S.D. Lord, S. Maret, P.G. Martin, J. Martin-Pintado, C. McCoey, M. Melchior, G.J. Melnick, K.M. Menten, B. Mookerjea, P. Morris, J.A. Murphy, D.A. Neufeld, B. Nisini, S. Pacheco, L. Pagani, B. Parise, J.C. Pearson, M. Pérault, T.G. Phillips, R. Plume, S.-L. Quin, R. Rizzo, M. Röllig, M. Salez, P. Saraceno, S. Schlemmer, R. Simon, K. Schuster, F.F.S. van der Tak, A.G.G.M. Tielens, D. Teyssier, N. Trappe, C. Vastel, S. Viti, V. Wakelam, A. Walters, S. Wang, N. Whyborn, M. van der Wiel, H.W. Yorke, S. Yu, J. Zmuidzinas

We identify a prominent absorption feature at 1115 GHz, detected in first HIFI spectra towards high-mass star-forming regions, and interpret its astrophysical origin. The characteristic hyperfine pattern of the H2O+ ground-state rotational transition, and the lack of other known low-energy transitions in this frequency range, identifies the feature as H2O+ absorption against the dust continuum background and allows us to derive the velocity profile of the absorbing gas. By comparing this velocity profile with velocity profiles of other tracers in the DR21 star-forming region, we constrain the frequency of the transition and the conditions for its formation. In DR21, the velocity distribution of H2O+ matches that of the [CII] line at 158\mu\m and of OH cm-wave absorption, both stemming from the hot and dense clump surfaces facing the HII-region and dynamically affected by the blister outflow. Diffuse foreground gas dominates the absorption towards Sgr B2. The integrated intensity of the absorption line allows us to derive lower limits to the H2O+ column density of 7.2e12 cm^-2 in NGC 6334, 2.3e13 cm^-2 in DR21, and 1.1e15 cm^-2 in Sgr B2.

V. Ossenkopf et al., HIFI observations of warm gas in DR21: Shock versus radiative heating (WADI)

  1005.2517            WADI

V. Ossenkopf, M. Röllig, R. Simon, N. Schneider, Y. Okada, J. Stutzki, M. Gerin, M. Akyilmaz, D. Beintema, A.O. Benz, O. Berne, F. Boulanger, B. Bumble, O. Coeur-Joly, C. Dedes, M.C. Diez-Gonzalez, K. France, A. Fuente, J.D. Gallego, J.R. Goicoechea, R. Güsten, A. Harris, R. Higgins, B. Jackson, C. Jarchow, C. Joblin, T. Klein, C. Kramer, S. Lord, P. Martin, J. Martin-Pintado, B. Mookerjea, D.A. Neufeld, T. Phillips, J.R. Rizzo, F.F.S. van der Tak, D. Teyssier, H. Yorke

The molecular gas in the DR21 massive star formation region is known to be affected by the strong UV field from the central star cluster and by a fast outflow creating a bright shock. The relative contribution of both heating mechanisms is the matter of a long debate. By better sampling the excitation ladder of various tracers we provide a quantitative distinction between the different heating mechanisms. HIFI observations of mid-J transitions of CO and HCO+ isotopes allow us to bridge the gap in excitation energies between observations from the ground, characterizing the cooler gas, and existing ISO LWS spectra, constraining the properties of the hot gas. Comparing the detailed line profiles allows to identify the physical structure of the different components. In spite of the known shock-excitation of H2 and the clearly visible strong outflow, we find that the emission of all lines up to > 2 THz can be explained by purely radiative heating of the material. However, the new Herschel/HIFI observations reveal two types of excitation conditions. We find hot and dense clumps close to the central cluster, probably dynamically affected by the outflow, and a more widespread distribution of cooler, but nevertheless dense, molecular clumps.

D. A. Neufeld et al., Strong absorption by interstellar hydrogen fluoride: Herschel/HIFI observations of the sight-line to G10.6-0.4 (W31C) (PRISMAS)

  1005.1671            PRISMAS

D. A. Neufeld, P. Sonnentrucker, T. G. Phillips, D. C. Lis, M. De Luca, J. R. Goicoechea, J. H. Black, M. Gerin, T. Bell, F. Boulanger, J. Cernicharo, A. Coutens, E. Dartois, M. Kazmierczak, P. Encrenaz, E. Falgarone, T. R. Geballe, T. Giesen, B. Godard, P. F. Goldsmith, C. Gry, H. Gupta, P. Hennebelle, E.Herbst, P. Hily-Blant, C. Joblin, R. Kolos, J. Krelowski, J. Martin-Pintado, K. M. Menten, R. Monje, B. Mookerjea, J. Pearson, M. Perault, C. Persson, R. Plume, M. Salez, S. Schlemmer, M. Schmidt, J. Stutzki, D. Teyssier, C. Vastel, S. Yu, P. Cais, E. Caux, R. Liseau, P. Morris, P. Planesas

We report the detection of strong absorption by interstellar hydrogen fluoride along the sight-line to the submillimeter continuum source G10.6-0.4 (W31C). We have used Herschel's HIFI instrument, in dual beam switch mode, to observe the 1232.4763 GHz J=1-0 HF transition in the upper sideband of the Band 5a receiver. The resultant spectrum shows weak HF emission from G10.6-0.4 at LSR velocities in the range -10 to -3 km/s, accompanied by strong absorption by foreground material at LSR velocities in the range 15 to 50 km/s. The spectrum is similar to that of the 1113.3430 GHz 1(11)-0(00) transition of para-water, although at some frequencies the HF (hydrogen fluoride) optical depth clearly exceeds that of para-H2O. The optically-thick HF absorption that we have observed places a conservative lower limit of 1.6E+14 cm-2 on the HF column density along the sight-line to G10.6-0.4. Our lower limit on the HF abundance, 6E-9 relative to hydrogen nuclei, implies that hydrogen fluoride accounts for between ~ 30 and 100% of the fluorine nuclei in the gas phase along this sight-line. This observation corroborates theoretical predictions that - because the unique thermochemistry of fluorine permits the exothermic reaction of F atoms with molecular hydrogen - HF will be the dominant reservoir of interstellar fluorine under a wide range of conditions.


Webpage is hosted at Leiden Observatory by HIFI Project Scientist Xander Tielens.
For questions, remarks or updates, please email Umut A. Yildiz