Pabst, C. H. M., Goicoechea, J. R., Teyssier, D., Berne, O., Ochsendorf, B. B., Wolfire, M. G., Higgins, R. D., Riquelme, D., Risacher, C., Pety, J., Le Petit, F., Roueff, E., Bron, E. and Tielens, A. G. G. M. (2017). [C II] emission from L1630 in the Orion B molecular cloud. Astron. Astrophys., 606. LES ULIS CEDEX A: EDP SCIENCES S A. ISSN 1432-0746
Full text not available from this repository.Abstract
Context. L1630 in the Orion B molecular cloud, which includes the iconic Horsehead Nebula, illuminated by the star system sigma Ori, is an example of a photodissociation region (PDR). In PDRs, stellar radiation impinges on the surface of dense material, often a molecular cloud, thereby inducing a complex network of chemical reactions and physical processes. Aims. Observations toward L1630 allow us to study the interplay between stellar radiation and a molecular cloud under relatively benign conditions, that is, intermediate densities and an intermediate UV radiation field. Contrary to the well-studied Orion Molecular Cloud 1 (OMC1), which hosts much harsher conditions, L1630 has little star formation. Our goal is to relate the [C II] fine-structure line emission to the physical conditions predominant in L1630 and compare it to studies of OMC1. Methods. The [C II] 158 mu m line emission of L1630 around the Horsehead Nebula, an area of 12' x 17', was observed using the upgraded German Receiver for Astronomy at Terahertz Frequencies (upGREAT) onboard the Stratospheric Observatory for Infrared Astronomy (SOFIA). Results. Of the [C II] emission from the mapped area 95%, 13 L-circle dot, originates from the molecular cloud; the adjacent H II region contributes only 5%, that is, 1 L-circle dot. From comparison with other data (CO (1-0)-line emission, far-infrared (FIR) continuum studies, emission from polycyclic aromatic hydrocarbons (PAHs)), we infer a gas density of the molecular cloud of n(H) similar to 3 x 10(3) cm(-3), with surface layers, including the Horsehead Nebula, having a density of up to n(H) similar to 4 x 10(4) cm(-3). The temperature of the surface gas is T similar to 100K. The average [C II] cooling efficiency within the molecular cloud is 1.3 x 10(-2). The fraction of the mass of the molecular cloud within the studied area that is traced by [C II] is only 8%. Our PDR models are able to reproduce the FIR-[C II] correlations and also the CO(1 0)-[C II] correlations. Finally, we compare our results on the heating efficiency of the gas with theoretical studies of photoelectric heating by PAHs, clusters of PAHs, and very small grains, and find the heating efficiency to be lower than theoretically predicted, a continuation of the trend set by other observations. Conclusions. In L1630 only a small fraction of the gas mass is traced by [C II]. Most of the [C II] emission in the mapped area stems from PDR surfaces. The layered edge-on structure of the molecular cloud and limitations in spatial resolution put constraints on our ability to relate different tracers to each other and to the physical conditions. From our study, we conclude that the relation between [C II] emission and physical conditions is likely to be more complicated than often assumed. The theoretical heating efficiency is higher than the one we calculate from the observed [C II] emission in the L1630 molecular cloud.
| Item Type: | Journal Article | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| URN: | urn:nbn:de:hbz:38-214558 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| DOI: | 10.1051/0004-6361/201730881 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Journal or Publication Title: | Astron. Astrophys. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Volume: | 606 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Date: | 2017 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Publisher: | EDP SCIENCES S A | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Place of Publication: | LES ULIS CEDEX A | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| ISSN: | 1432-0746 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Language: | English | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Faculty: | Unspecified | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Divisions: | Unspecified | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Subjects: | no entry | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| Refereed: | Yes | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| URI: | http://kups.ub.uni-koeln.de/id/eprint/21455 |
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