Kennicutt-Schmidt Relation Variety and Star-forming Cloud Fraction

The observationally derived Kennicutt-Schmidt (KS) relation slopes differ from study to study, ranging from sublinear to superlinear. We investigate the KS-relation variety (slope and normalization) as a function of integrated intensity ratio, R31 = CO(J = 3-2)/CO(J = 1-0) using spatially resolved C...

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Bibliographic Details
Published inThe Astrophysical journal Vol. 837; no. 2; pp. 137 - 149
Main Authors Morokuma-Matsui, Kana, Muraoka, Kazuyuki
Format Journal Article
LanguageEnglish
Published Philadelphia The American Astronomical Society 10.03.2017
IOP Publishing
Subjects
Astrophysics
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
CARBON MONOXIDE
Cloud formation
DISTRIBUTION
EFFICIENCY
EVOLUTION
Galactic structure
GALAXIES
galaxies: evolution
galaxies: individual (M83, NGC 3627, NGC 5055)
galaxies: ISM
galaxies: star formation
Molecular gases
Slopes
SPACE
Spiral galaxies
Star & galaxy formation
Star formation
STARS
Stars & galaxies
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Summary:The observationally derived Kennicutt-Schmidt (KS) relation slopes differ from study to study, ranging from sublinear to superlinear. We investigate the KS-relation variety (slope and normalization) as a function of integrated intensity ratio, R31 = CO(J = 3-2)/CO(J = 1-0) using spatially resolved CO(J = 1-0), CO(J = 3-2), H i, H , and 24 m data of three nearby spiral galaxies (NGC 3627, NGC 5055, and M83). We find that (1) the slopes for each subsample with a fixed R31 are shallower, but the slope for all data sets combined becomes steeper, (2) normalizations for high R31 subsamples tend to be high, (3) R31 correlates with star formation efficiency, therefore the KS relation depends on the distribution in R31- gas space of the samples: no gas dependence of R31 results in a linear slope of the KS relation, whereas a positive correlation between gas and R31 results in a superlinear slope of the KS relation, and (4) R31- gas distributions are different from galaxy to galaxy and within a galaxy: galaxies with prominent galactic structure tend to have large R31 and gas. Our results suggest that the formation efficiency of a star-forming cloud from molecular gas is different among galaxies as well as within a galaxy, and it is one of the key factors inducing the variety in galactic KS relation.
Bibliography:AAS02271
Interstellar Matter and the Local Universe
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/aa6115