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Dedes, C.; Röllig, M.; Mookerjea, B.; Okada, Y.; Ossenkopf, V.; Bruderer, S.; Benz, A. O.; Melchior, M.; Kramer, C.; Gerin, M.; Güsten, R.; Akyilmaz, M.; Berne, O.; Boulanger, F.; De Lange, G.; Dubbeldam, L.; France, K.; Fuente, A.; Goicoechea, J. R.; Harris, A.; Huisman, R.; Jellema, W.; Joblin, C.; Klein, T.; Le Petit, F.; Lord, S.; Martin, P.; Martin-Pintado, J.; Neufeld, D. A.; Philipp, S.; Phillips, T.; Pilleri, P.; Rizzo, J. R.; Salez, M.; Schieder, R.; Simon, R.; Siebertz, O.; Stutzki, J.; van der Tak, F.; Teyssier, D.; Yorke, H. |
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The origin of the [C II] emission in the S140 photon-dominated regions. New insights from HIFI |
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Journal Article |
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2010 |
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Astron. Astrophys. |
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521 |
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L24 |
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HEB mixer applications, HIFI, Herschel, ISM: structure / ISM: kinematics and dynamics / ISM: molecules / photon-dominated region (PDR) / submillimeter: general |
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Using Herschel's HIFI instrument, we observe C ii along a cut through S140, as well as 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-Ï„ model for photon-dominated regions (PDRs). 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 PDRs. 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 C ii peak at IRS1 coinciding with shocked H2 emission at the edges of the outflow cavity. We note that previously available observations of IRS1 can be reproduced well by a single-component KOSMA-Ï„ model. Thus, it is HIFI's unprecedented spatial and spectral resolution, as well as its sensitivity that has allowed us to uncover an additional hot gas component in the S140 region. |
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1091 |
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Bruderer, S.; Benz, A. O.; van Dishoeck, E. F.; Melchior, M.; Doty, S. D.; van der Tak, F.; Stäuber, P.; Wampfler, S. F.; Dedes, C.; Yıldız, U. A.; Pagani, L.; Giannini, T.; de Graauw, Th.; Whyborn, N.; Teyssier, D.; Jellema, W.; Shipman, R.; Schieder, R.; Honingh, N.; Caux, E.; Bächtold, W.; Csillaghy, A.; Monstein, C.; Bachiller, R.; Baudry, A.; Benedettini, M.; Bergin, E.; Bjerkeli, P.; Blake, G. A.; Bontemps, S.; Braine, J.; Caselli, P.; Cernicharo, J.; Codella, C.; Daniel, F.; di Giorgio, A. M.; Dominik, C.; Encrenaz, P.; Fich, M.; Fuente, A.; Goicoechea, J. R.; Helmich, F.; Herczeg, G. J.; Herpin, F.; Hogerheijde, M. R.; Jacq, T.; Johnstone, D.; Jørgensen, J. K.; Kristensen, L. E.; Larsson, B.; Lis, D.; Liseau, R.; Marseille, M.; McCoey, C.; Melnick, G.; Neufeld, D.; Nisini, B.; Olberg, M.; Parise, B.; Pearson, J. C.; Plume, R.; Risacher, C.; Santiago-García, J.; Saraceno, P.; Shipman, R.; Tafalla, M.; van Kempen, T. A.; Visser, R.; Wyrowski, F. |
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Herschel/HIFI detections of hydrides towards AFGL 2591. Envelope emission versus tenuous cloud absorption |
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Journal Article |
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2010 |
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Astron. Astrophys. |
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521 |
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L44 (1 to 7) |
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HEB mixer applications, HIFI, Herschel |
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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 = 3/22,- – 1/21,+ ) 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. |
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1083 |
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Justtanont, K.; Decin, L.; Schöier, F. L.; Maercker, M.; Olofsson, H.; Bujarrabal, V.; Marston, A. P.; Teyssier, D.; Alcolea, J.; Cernicharo, J.; Dominik, C.; de Koter, A.; Melnick, G.; Menten, K.; Neufeld, D.; Planesas, P.; Schmidt, M.; Szczerba, R.; Waters, R.; de Graauw, Th.; Whyborn, N.; Finn, T.; Helmich, F.; Siebertz, O.; Schmülling, F.; Ossenkopf, V.; Lai, R. |
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A HIFI preview of warm molecular gas around χ Cygni: first detection of H2O emission toward an S-type AGB star |
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Journal Article |
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2010 |
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Astron. Astrophys. |
Abbreviated Journal |
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521 |
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L6 |
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HEB mixer applications, HIFI, Herschel, stars: AGB and post-AGB / circumstellar matter / stars: kinematics and dynamics / stars: individual: χ Cyg / stars: late-type / stars: mass-loss |
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Aims. 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 χ 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 χ Cyg.
Methods. 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.
Results. 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) × 10-5, 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. |
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1096 |
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Melnick, G. J.; Tolls, V.; Neufeld, D. A.; Bergin, E. A.; Phillips, T. G.; Wang, S.; Crockett, N. R.; Bell, T. A.; Blake, G. A.; Cabrit, S.; Caux, E.; Ceccarelli, C.; Cernicharo, J.; Comito, C.; Daniel, F.; Dubernet, M.-L.; Emprechtinger, M.; Encrenaz, P.; Falgarone, E.; Gerin, M.; Giesen, T. F.; Goicoechea, J. R.; Goldsmith, P. F.; Herbst, E.; Joblin, C.; Johnstone, D.; Langer, W. D.; Latter, W. D.; Lis, D. C.; Lord, S. D.; Maret, S.; Martin, P. G.; Menten, K. M.; Morris, P.; Müller, H. S. P.; Murphy, J. A.; Ossenkopf, V.; Pagani, L.; Pearson, J. C.; Pérault, M.; Plume, R.; Qin, S.-L.; Salez, M.; Schilke, P.; Schlemmer, S.; Stutzki, J.; Trappe, N.; van der Tak, F. F. S.; Vastel, C.; Yorke, H. W.; Yu, S.; Zmuidzinas, J. |
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Title |
Herschel observations of EXtra-Ordinary Sources (HEXOS): Observations of H2O and its isotopologues towards Orion KL |
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Journal Article |
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2010 |
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Astron. Astrophys. |
Abbreviated Journal |
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521 |
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L27 |
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HEB mixer applications, HIFI, Herschel, ISM: abundances / ISM: molecules |
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We report the detection of more than 48 velocity-resolved ground rotational state transitions of H216O, H218O, and H217O – 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 H218O line fluxes, which are less affected by line opacity than their H216O counterparts, and an escape probability method, the column densities of H218O associated with each emission component are derived. We infer total water abundances of 7.4 × 10-5, 1.0 × 10-5, and 1.6 × 10-5 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. |
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1098 |
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Decin, L.; Justtanont, K.; De Beck, E.; Lombaert, R.; de Koter, A.; Waters, L. B. F. M.; Marston, A. P.; Teyssier, D.; Schöier, F. L.; Bujarrabal, V.; Alcolea, J.; Cernicharo, J.; Dominik, C.; Melnick, G.; Menten, K.; Neufeld, D. A.; Olofsson, H.; Planesas, P.; Schmidt, M.; Szczerba, R.; de Graauw, T.; Helmich, F.; Roelfsema, P.; Dieleman, P.; Morris, P.; Gallego, J. D.; Díez-González, M. C.; Caux, E. |
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Title |
Water content and wind acceleration in the envelope around the oxygen-rich AGB star IK Tauri as seen by Herschel/HIFI |
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Journal Article |
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2010 |
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Astron. Astrophys. |
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521 |
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L4 |
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HEB mixer applications, HIFI, Herschel, line: profiles / radiative transfer / instrumentation: spectrographs / stars: AGB and post-AGB / circumstellar matter / submillimeter: stars |
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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 H216O and the rarer isotopologues H217O and H218O in both the ortho and para states. We deduce a total water content (relative to molecular hydrogen) of $6.6 \times 10^{-5}$, and an ortho-to-para ratio of 3:1. These results are consistent with the formation of H2O 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. |
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1090 |
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