Universität zu Köln

Requena-Torres, M. A., Israel, F. P., Okada, Y., Guesten, R., Stutzki, J., Risacher, C., Simon, R. and Zinnecker, H. (2016). Carbon gas in SMC low-metallicity star-forming regions. Astron. Astrophys., 589. LES ULIS CEDEX A: EDP SCIENCES S A. ISSN 1432-0746

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Abstract

This paper presents [C II], [C I] and CO emission line maps of the star-forming regions N 66, N 25+N 26, and N 88 in the metal-poor Local Group dwarf galaxy SMC. The spatial and velocity structure of the large H II region N 66 reveals an expanding ring of shocked molecular gas centered on the exciting star cluster NGC 346, whereas a more distant dense molecular cloud is being eroded by UV radiation from the same cluster. In the N 25+N 26 and N 88 maps, diffuse [C II] emission at a relatively low surface brightness extends well beyond the compact boundaries of the bright emission associated with the H II regions. In all regions, the distribution of this bright [C II] emission and the less prominent [C I] emission closely follows the outline of the CO complexes, but the intensity of the [C II] and [C I] emission is generally anticorrelated, which can be understood by the action of photodissociation and photoionization processes. Notwithstanding the overall similarity of CO and [C II] maps, the intensity ratio of these lines varies significantly, mostly due to changes in CO brightness. [C II] emission line profiles are up to 50% wider in velocity than corresponding CO profiles. A radiative transfer analysis shows that the [C II] line is the dominant tracer of (CO-dark) molecular hydrogen in the SMC. CO emission traces only a minor fraction of the total amount of gas. The similarity of the spatial distribution and line profile shape, and the dominance of molecular gas associated with [C II] rather than CO emission imply that in the low-metallicity environment of the SMC the small amount of dense molecular gas traced by CO is embedded in the much more extended molecular gas traced only by [C II] emission. The contribution from neutral atomic and ionized hydrogen zones is negligible in the star-forming regions observed.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Requena-Torres, M. A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Israel, F. P. UNSPECIFIED UNSPECIFIED UNSPECIFIED Okada, Y. UNSPECIFIED UNSPECIFIED UNSPECIFIED Guesten, R. UNSPECIFIED UNSPECIFIED UNSPECIFIED Stutzki, J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Risacher, C. UNSPECIFIED UNSPECIFIED UNSPECIFIED Simon, R. UNSPECIFIED UNSPECIFIED UNSPECIFIED Zinnecker, H. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-276546
DOI:	10.1051/0004-6361/201526244
Journal or Publication Title:	Astron. Astrophys.
Volume:	589
Date:	2016
Publisher:	EDP SCIENCES S A
Place of Publication:	LES ULIS CEDEX A
ISSN:	1432-0746
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language SMALL-MAGELLANIC-CLOUD; H-II REGION; SEST KEY PROGRAM; C II; NGC 346; N 66; NGC-346; N66; TELESCOPE; EMISSION Multiple languages Astronomy & Astrophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/27654