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Excitation of the molecular gas in the nuclear region of M82

Loenen, A. F. and Lord, S. and Morris, P. and Phillips, T. G. (2010) Excitation of the molecular gas in the nuclear region of M82. Astronomy and Astrophysics, 521 . L2. ISSN 0004-6361. doi:10.1051/0004-6361/201015114.

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We present high-resolution HIFI spectroscopy of the nucleus of the archetypical starburst galaxy M 82. Six ^(12)CO lines, 2 ^(13)CO lines and 4 fine-structure lines have been 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 (G_0 = 10^2). The remaining gas is predominantly found in clouds with higher densities (n = 10^5 cm^(-3)) and radiation fields (G_0 = 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 (G_0 = 10^(3.25)). These results show the strength of multi-component modelling for interpretating the integrated properties of galaxies.

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Additional Information:© 2010 ESO. Received 31 May 2010; Accepted 25 June 2010; Published online 01 October 2010. R. Sz acknowledges support from grant N 203 393334 from Polish MNiSW. Support for this work was provided by NASA through an award issued by JPL/Caltech. Data presented in this paper were analysed using “HIPE”, a joint development by the Herschel Science Ground Segment Consortium, consisting of ESA, the NASA Herschel Science Center, and the HIFI, PACS, and SPIRE consortia (See 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 Astrobiología (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.
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Ministerstwo Nauki i Szkolnictwa Wyższego (MNiSW) (Poland)N 203 393334
Subject Keywords:galaxies: individual: M82; submillimeter: ISM; ISM: molecules; galaxies: ISM; galaxies: starburst
Record Number:CaltechAUTHORS:20110110-112411110
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Official Citation:Excitation of the molecular gas in the nuclear region of M 82 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 and A. G. G. M. Tielens A&A 521 L2 (2010) DOI: 10.1051/0004-6361/201015114
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:21666
Deposited On:10 Jan 2011 20:16
Last Modified:09 Nov 2021 15:59

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