Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2012
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012aas...21931104j&link_type=abstract
American Astronomical Society, AAS Meeting #219, #311.04
Astronomy and Astrophysics
Astronomy
Scientific paper
We analyze a sample of massive HI-rich galaxies in the local universe, which have HI mass measurements available from the Arecibo telescope . We find that galaxies with larger HI fractions have bluer, more actively a star-forming outer disks. Our results strongly support an ``inside-out'' picture of disk galaxy formation. The lack of any intrinsic connection between HI fraction and galaxy asymmetry suggests that gas is accreted smoothly onto the outer disk. We have also developed algorithms to identify and measure the ellipticity and sizes of bars and applied this to a sample of 3890 face-on massive disk galaxies in the Sloan Digital Sky Survey. We show that the fraction of galaxies with strong bars is highest for high mass galaxies with low surface densities and concentrations. Among these galaxies, the bar fraction peaks in galaxies with both higher and lower-than-average rates of central star formation This suggests that bars may play a role in inducing gas inflows that build central bulge components in galaxies. We speculate that the formation of the bulge may lead to the eventual quenching of star formation in galaxies. We also find that the size of the bar relative to the disk depends most strongly on the mean stellar age of the galaxy, supporting scenarios in which the growth of bars is regulated by gas accretion.
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