Universität zu Köln

Sandstrom, K. M., Leroy, A. K., Walter, F., Bolatto, A. D., Croxall, K. V., Draine, B. T., Wilson, C. D., Wolfire, M., Calzetti, D., Kennicutt, R. C., Aniano, G., Meyer, J. Donovan, Usero, A., Bigiel, F., Brinks, E., de Blok, W. J. G., Crocker, A., Dale, D., Engelbracht, C. W., Galametz, M., Groves, B., Hunt, L. K., Koda, J., Kreckel, K., Linz, H., Meidt, S., Pellegrini, E., Rix, H. -W., Roussel, H., Schinnerer, E., Schruba, A., Schuster, K. -F., Skibba, R., van der Laan, T., Appleton, P., Armus, L., Brandl, B., Gordon, K., Hinz, J., Krause, O., Montiel, E., Sauvage, M., Schmiedeke, A., Smith, J. D. T. and Vigroux, L. (2013). THE CO-TO-H-2 CONVERSION FACTOR AND DUST-TO-GAS RATIO ON KILOPARSEC SCALES IN NEARBY GALAXIES. Astrophys. J., 777 (1). BRISTOL: IOP PUBLISHING LTD. ISSN 1538-4357

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Abstract

We present similar to kiloparsec spatial resolution maps of the CO-to-H-2 conversion factor (alpha(CO)) and dust-to-gas ratio (DGR) in 26 nearby, star-forming galaxies. We have simultaneously solved for alpha(CO) and the DGR by assuming that the DGR is approximately constant on kiloparsec scales. With this assumption, we can combine maps of dust mass surface density, CO-integrated intensity, and H I column density to solve for both alpha(CO) and the DGR with no assumptions about their value or dependence on metallicity or other parameters. Such a study has just become possible with the availability of high-resolution far-IR maps from the Herschel key program KINGFISH, (CO)-C-12 J = (2-1) maps from the IRAM 30 m large program HERACLES, and H I 21 cm line maps from THINGS. We use a fixed ratio between the (2-1) and (1-0) lines to present our alpha(CO) results on the more typically used (CO)-C-12 J = (1-0) scale and show using literature measurements that variations in the line ratio do not affect our results. In total, we derive 782 individual solutions for alpha(CO) and the DGR. On average, alpha(CO) = 3.1M(circle dot) pc(-2) (K km s(-1))(-1) for our sample with a standard deviation of 0.3 dex. Within galaxies, we observe a generally flat profile of alpha(CO) as a function of galactocentric radius. However, most galaxies exhibit a lower alpha(CO) value in the central kiloparsec-a factor of similar to 2 below the galaxy mean, on average. In some cases, the central alpha(CO) value can be factors of 5-10 below the standard Milky Way (MW) value of alpha(CO,MW) = 4.4 M-circle dot pc(-2) (K km s(-1))(-1). While for alpha(CO) we find only weak correlations with metallicity, the DGR is well-correlated with metallicity, with an approximately linear slope. Finally, we present several recommendations for choosing an appropriate alpha(CO) for studies of nearby galaxies.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Sandstrom, K. M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Leroy, A. K. UNSPECIFIED UNSPECIFIED UNSPECIFIED Walter, F. UNSPECIFIED UNSPECIFIED UNSPECIFIED Bolatto, A. D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Croxall, K. V. UNSPECIFIED UNSPECIFIED UNSPECIFIED Draine, B. T. UNSPECIFIED UNSPECIFIED UNSPECIFIED Wilson, C. D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Wolfire, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Calzetti, D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Kennicutt, R. C. UNSPECIFIED UNSPECIFIED UNSPECIFIED Aniano, G. UNSPECIFIED UNSPECIFIED UNSPECIFIED Meyer, J. Donovan UNSPECIFIED UNSPECIFIED UNSPECIFIED Usero, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Bigiel, F. UNSPECIFIED UNSPECIFIED UNSPECIFIED Brinks, E. UNSPECIFIED UNSPECIFIED UNSPECIFIED de Blok, W. J. G. UNSPECIFIED UNSPECIFIED UNSPECIFIED Crocker, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Dale, D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Engelbracht, C. W. UNSPECIFIED UNSPECIFIED UNSPECIFIED Galametz, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Groves, B. UNSPECIFIED UNSPECIFIED UNSPECIFIED Hunt, L. K. UNSPECIFIED UNSPECIFIED UNSPECIFIED Koda, J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Kreckel, K. UNSPECIFIED UNSPECIFIED UNSPECIFIED Linz, H. UNSPECIFIED UNSPECIFIED UNSPECIFIED Meidt, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Pellegrini, E. UNSPECIFIED UNSPECIFIED UNSPECIFIED Rix, H. -W. UNSPECIFIED UNSPECIFIED UNSPECIFIED Roussel, H. UNSPECIFIED UNSPECIFIED UNSPECIFIED Schinnerer, E. UNSPECIFIED UNSPECIFIED UNSPECIFIED Schruba, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Schuster, K. -F. UNSPECIFIED UNSPECIFIED UNSPECIFIED Skibba, R. UNSPECIFIED UNSPECIFIED UNSPECIFIED van der Laan, T. UNSPECIFIED UNSPECIFIED UNSPECIFIED Appleton, P. UNSPECIFIED UNSPECIFIED UNSPECIFIED Armus, L. UNSPECIFIED UNSPECIFIED UNSPECIFIED Brandl, B. UNSPECIFIED UNSPECIFIED UNSPECIFIED Gordon, K. UNSPECIFIED UNSPECIFIED UNSPECIFIED Hinz, J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Krause, O. UNSPECIFIED UNSPECIFIED UNSPECIFIED Montiel, E. UNSPECIFIED UNSPECIFIED UNSPECIFIED Sauvage, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Schmiedeke, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Smith, J. D. T. UNSPECIFIED UNSPECIFIED UNSPECIFIED Vigroux, L. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-473290
DOI:	10.1088/0004-637X/777/1/5
Journal or Publication Title:	Astrophys. J.
Volume:	777
Number:	1
Date:	2013
Publisher:	IOP PUBLISHING LTD
Place of Publication:	BRISTOL
ISSN:	1538-4357
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language MOLECULAR CLOUD COMPLEX; STAR-FORMATION RATE; SPIRAL GALAXIES; X-FACTOR; INFRARED-EMISSION; OXYGEN ABUNDANCE; LINE-INTENSITIES; HII-REGIONS; CO EMISSION; ATOMIC-GAS Multiple languages Astronomy & Astrophysics Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/47329