Universität zu Köln

Krips, M., Martin, S., Sakamoto, K., Aalto, S., Bisbas, T. G., Bolatto, A. D., Downes, D., Eckart, A., Feruglio, Ch., Garcia-Burillo, S., Geach, J., Greve, T. R., Konig, S., Matsushita, S., Neri, R., Offner, S., Peck, A. B., Viti, S. and Wagg, J. (2016). ACA [CI] observations of the starburst galaxy NGC 253. Astron. Astrophys., 592. LES ULIS CEDEX A: EDP SCIENCES S A. ISSN 1432-0746

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Abstract

Context. Carbon monoxide (CO) is widely used as a tracer of the molecular gas in almost all types of environments. However, several shortcomings of CO complicate usaging it as H-2 tracer, such as its optical depth effects, the dependence of its abundance on metallicity, or its susceptibility to dissociation in highly irradiated regions. Neutral carbon emission has been proposed to overcome some of these shortcomings and hence to help revealing the limits of CO as a measure of the molecular gas. Aims. We aim to study the general characteristics of the spatially and spectrally resolved carbon line emission in a variety of extragalactic sources and evaluate its potential as complementary H-2 tracer to CO. Methods. We used the Atacama Compact Array to map the [CI](P-3(1)-P-3(0)) line emission in the nearby starburst galaxy NGC 253 at unprecedented angular resolution (similar to 3 ''). This is the first well-resolved interferometric [CI] map of an extragalactic source. Results. We have detected the [CI] line emission at high significance levels along the central disk of NGC 253 and its edges where expanding shells have previously been found in CO. Globally, the distribution of the [CI] line emission strongly resembles that of CO, confirming the results of previous Galactic surveys that [CI] traces the same molecular gas as CO. However, we also identify a significant increase of [CI] line emission with respect to CO in (some of) the outflow or shocked regions of NGC 253, namely the bipolar outflow emerging from the nucleus. A first-order estimate of the [CI] column densities indicates abundances of [CI] that are very similar to the abundance of CO in NGC 253. Interestingly, we find that the [CI] line is marginally optically thick within the disk. Conclusions. The enhancement of the [CI]/CO line ratios (similar to 0.4-0.6) with respect to Galactic values (<= 0.1), especially in the shocked regions of NGC 253, clearly indicates that mechanical perturbation such as shocks and the strong radiation fields in this starburst galaxy have a marked effect on the carbon excitation and/or abundance.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Krips, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Martin, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Sakamoto, K. UNSPECIFIED UNSPECIFIED UNSPECIFIED Aalto, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Bisbas, T. G. UNSPECIFIED UNSPECIFIED UNSPECIFIED Bolatto, A. D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Downes, D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Eckart, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Feruglio, Ch. UNSPECIFIED UNSPECIFIED UNSPECIFIED Garcia-Burillo, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Geach, J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Greve, T. R. UNSPECIFIED UNSPECIFIED UNSPECIFIED Konig, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Matsushita, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Neri, R. UNSPECIFIED UNSPECIFIED UNSPECIFIED Offner, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Peck, A. B. UNSPECIFIED UNSPECIFIED UNSPECIFIED Viti, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Wagg, J. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-268669
DOI:	10.1051/0004-6361/201628882
Journal or Publication Title:	Astron. Astrophys.
Volume:	592
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 ATOMIC CARBON; MOLECULAR CLOUDS; NEUTRAL CARBON; STAR-FORMATION; COSMIC-RAYS; I EMISSION; CO; GAS; PHOTODISSOCIATION; DISTANCE Multiple languages Astronomy & Astrophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/26866