Universität zu Köln

Roman-Duval, Julia ORCID: 0000-0001-6326-7069, Jackson, James M., Heyer, Mark, Rathborne, Jill and Simon, Robert ORCID: 0000-0003-2555-4408 (2010). PHYSICAL PROPERTIES AND GALACTIC DISTRIBUTION OF MOLECULAR CLOUDS IDENTIFIED IN THE GALACTIC RING SURVEY. Astrophys. J., 723 (1). S. 492 - 508. BRISTOL: IOP PUBLISHING LTD. ISSN 0004-637X

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Abstract

We derive the physical properties of 580 molecular clouds based on their (12)CO and (13)CO line emission detected in the University of Massachusetts-Stony Brook (UMSB) and Galactic Ring surveys. We provide a range of values of the physical properties of molecular clouds, and find a power-law correlation between their radii and masses, suggesting that the fractal dimension of the interstellar medium is around 2.36. This relation, M = (228 +/- 18) R(2.36 +/- 0.04), allows us to derive masses for an additional 170 Galactic Ring Survey (GRS) molecular clouds not covered by the UMSB survey. We derive the Galactic surface mass density of molecular gas and examine its spatial variations throughout the Galaxy. We find that the azimuthally averaged Galactic surface density of molecular gas peaks between Galactocentric radii of 4 and 5 kpc. Although the Perseus arm is not detected in molecular gas, the Galactic surface density of molecular gas is enhanced along the positions of the Scutum-Crux and Sagittarius arms. This may indicate that molecular clouds form in spiral arms and are disrupted in the inter-arm space. Finally, we find that the CO excitation temperature of molecular clouds decreases away from the Galactic center, suggesting a possible decline in the star formation rate with Galactocentric radius. There is a marginally significant enhancement in the CO excitation temperature of molecular clouds at a Galactocentric radius of about 6 kpc, which in the longitude range of the GRS corresponds to the Sagittarius arm. This temperature increase could be associated with massive star formation in the Sagittarius spiral arm.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Roman-Duval, Julia UNSPECIFIED orcid.org/0000-0001-6326-7069 UNSPECIFIED Jackson, James M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Heyer, Mark UNSPECIFIED UNSPECIFIED UNSPECIFIED Rathborne, Jill UNSPECIFIED UNSPECIFIED UNSPECIFIED Simon, Robert UNSPECIFIED orcid.org/0000-0003-2555-4408 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-493006
DOI:	10.1088/0004-637X/723/1/492
Journal or Publication Title:	Astrophys. J.
Volume:	723
Number:	1
Page Range:	S. 492 - 508
Date:	2010
Publisher:	IOP PUBLISHING LTD
Place of Publication:	BRISTOL
ISSN:	0004-637X
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language PLANE-CO SURVEY; LARGE-MAGELLANIC-CLOUD; MILKY-WAY; INTERSTELLAR CLOUDS; STAR-FORMATION; GRAVITATIONAL COLLAPSE; RADIAL-DISTRIBUTION; INFRARED-EMISSION; DUST PROPERTIES; COSMIC-RAYS Multiple languages Astronomy & Astrophysics Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/49300