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Excitation and abundance of C_3 in star forming cores: Herschel/HIFI observations of the sight-lines to W31C and W49N

Mookerjea, B. and Bell, T. A. and Lis, D. C. and Monje, R. and Phillips, T. G. and Morris, P. and Zmuidzinas, J. (2010) Excitation and abundance of C_3 in star forming cores: Herschel/HIFI observations of the sight-lines to W31C and W49N. Astronomy and Astrophysics, 521 . Art. No. L13. ISSN 0004-6361. doi:10.1051/0004-6361/201015095.

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We present spectrally resolved observations of triatomic carbon (C_3) in several ro-vibrational transitions between the vibrational ground state and the low-energy ν_2 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 C_3 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 C_3 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(C_3) ~ 7−9 × 10^(14) cm^(−2) and abundance x(C_3) ~ 10^(−8) with respect to H_2. 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(C_3) = 10^(−8), T_(kin) = 30−50 K, N(C_3) = 1.5 × 10^(15) cm^(−2) fits the observations reasonably well and provides parameters in very good agreement with the simple excitation analysis.

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Lis, D. C.0000-0002-0500-4700
Additional Information:© 2010 ESO. Received 31 May 2010, Accepted 2 July 2010, Published online 01 October 2010. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. HIFI has been designed and built by a consortium of institutes and university departments from across Europe, Canada and the United States under the leadership of SRON Netherlands Institute for Space Research, Groningen, The Netherlands and with major contributions from Germany, France and the US. Consortium members are: Canada: CSA, U. Waterloo; France: CESR, LAB, LERMA, IRAM; Germany: KOSMA, MPIfR, MPS; Ireland, NUI Maynooth; Italy: ASI, IFSI-INAF, Osservatorio Astrofisico di Arcetri-INAF; Netherlands: SRON, TUD; Poland: CAMK, CBK; Spain: Observatorio Astronómico Nacional (IGN), Centro de Astrobiologá (CSIC-INTA). Sweden: Chalmers University of Technology – MC2, RSS & GARD; Onsala Space Observatory; Swedish National Space Board, Stockholm University – Stockholm Observatory; Switzerland: ETH Zurich, FHNW; USA: Caltech, JPL, NHSC. J.C. and J.R.G. thanks spanish MICINN for funding support under projects AYA2009-07304 and CSD2009-00038. M.S. acknowledge support from grant N 203 393334 from Polish MNiSW.
Funding AgencyGrant Number
Ministerio de Ciencia e Innovación (MCINN)AYA2009-07304
Ministerio de Ciencia e Innovación (MCINN)CSD2009-00038
Ministerstwo Nauki i Szkolnictwa Wyższego (MNiSW)N 203 393334
Subject Keywords:ISM: lines and bands – ISM: molecules – radiative transfer – ISM: individual objects: W49N – ISM: individual objects: W31C
Record Number:CaltechAUTHORS:20110103-141054117
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Official Citation:Excitation and abundance of C3 in star forming cores - Herschel/HIFI observations of the sight-lines to W31C and W49N 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. Kaźmierczak, R. Kołos, J. Krełowski, 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. Güsten, C. E. Honingh, P. Morris, P. Roelfsema, R. Schieder, A. G. G. M. Tielens and J. Zmuidzinas A&A 521 L13 (2010) DOI: 10.1051/0004-6361/201015095
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:21550
Deposited By: Benjamin Perez
Deposited On:03 Jan 2011 22:42
Last Modified:09 Nov 2021 15:58

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