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Submillimeter imaging spectroscopy of the Horsehead nebula

Philipp, S. D. and Lis, D. C. and Güsten, R. and Kasemann, C. and Klein, T. and Phillips, T. G. (2006) Submillimeter imaging spectroscopy of the Horsehead nebula. Astronomy and Astrophysics, 454 (1). pp. 213-219. ISSN 0004-6361. doi:10.1051/0004-6361:20053533.

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We present ~15 arcsecond resolution single-dish imaging of the Horsehead nebula in the CI (1-0) and CO (4-3) lines, carried out using the CHAMP array at the Caltech Submillimeter Observatory (CSO). The data are used together with supporting observations of the (2-1) transitions of the CO isotopologues to determine the physical conditions in the atomic and molecular gas via Photon Dominated Region (PDR) modeling. The CO (4-3)/(2-1) line ratio, which is an excellent tracer of the direction of the incoming UV photons, increases at the western and northern edges of the nebula, confirming that the illumination is provided mostly by the stars σ and گ Orionis. The observed line intensities are consistent with PDR models with an H nuclei volume density of ~3- 7 x 10^4 cm^(-3). The models predict a kinetic temperature of ~12 K and a C^(18)O fractional abundance with respect to H atoms of 2.4 x 10^(-7) in the shielded region, which in turn imply a total molecular mass of ~24 M_☉ in the C^(18)O filament. The outer halo, devoid of C^(18)O, but traced by the CI emission has a comparable density and contributes additional ~13 M_☉ of material, resulting in an upper limit of ~37 M_☉ for the total molecular mass of the nebula.

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Lis, D. C.0000-0002-0500-4700
Additional Information:© 2006 ESO. Received 30 May 2005. Accepted 16 March 2006. This article is dedicated to the memory of Wolfgang Wiedenhöver, who lead the efforts on the developments of the correlator array backend MACS for CHAMP. This research has been supported by NSF grant AST 22-09008 to the Caltech Submillimeter Observatory. We thank D. Dowell for providing us with the 350 μm SHARC II image prior to publication and J. Bally for the mosaic on the horsehead of the NOAO Star Formation Survey Data 1997 in Hα emission, J. Le Bourlot and E. Roueff for their assistance with the Meudon PDR code, and M. Gerin, K. M. Menten, P. Schilke and M. Walmsley for stimulating discussions. Also we like to thank the CSO staff for their help and support during the CHAMP campaigns.
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NSFAST 22-09008
Subject Keywords:ISM: individual: objects: Horsehead nebula; ISM: molecules -- ISM: structure; ISM: abundances; ISM: clouds; stars: formation
Issue or Number:1
Record Number:CaltechAUTHORS:20110727-080256938
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Official Citation:Submillimeter imaging spectroscopy of the Horsehead nebula p. 213 S. D. Philipp, D. C. Lis, R. Güsten, C. Kasemann, T. Klein and T. G. Phillips
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:24560
Deposited By: Ruth Sustaita
Deposited On:27 Jul 2011 16:23
Last Modified:09 Nov 2021 16:24

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