THE PROPERTIES OF THE CIRCUMGALACTIC MEDIUM IN RED AND BLUE GALAXIES: RESULTS FROM THE COS-GASS+COS-HALOS SURVEYS

ABSTRACT We use the combined data from the COS-GASS and COS-Halos surveys to characterize the Circum-Galactic Medium (CGM) surrounding typical low-redshift galaxies in the mass range , and over a range of impact parameters extending to just beyond the halo virial radius (Rvir). We find the radial sc...

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Bibliographic Details
Published in:	The Astrophysical journal 2016-12, Vol.833 (2), p.259
Main Authors:	Borthakur, Sanchayeeta, Heckman, Timothy, Tumlinson, Jason, Bordoloi, Rongmon, Kauffmann, Guinevere, Catinella, Barbara, Schiminovich, David, Davé, Romeel, Moran, Sean M., Saintonge, Amelie
Format:	Article
Language:	eng
Subjects:	Absorbers ABSORPTION ASTROPHYSICS, COSMOLOGY AND ASTRONOMY Clouds Correlation DISPERSIONS Equivalence Galactic halos GALAXIES galaxies: halos galaxies: star formation Galaxy distribution Halos IMPACT PARAMETER MASS Offsets Polls & surveys QUASARS quasars: absorption lines Radial distribution RED SHIFT SPATIAL DISTRIBUTION Star & galaxy formation STAR EVOLUTION Star formation Star formation rate STARS Stars & galaxies VELOCITY
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Summary:	ABSTRACT We use the combined data from the COS-GASS and COS-Halos surveys to characterize the Circum-Galactic Medium (CGM) surrounding typical low-redshift galaxies in the mass range , and over a range of impact parameters extending to just beyond the halo virial radius (Rvir). We find the radial scale length of the distributions of the equivalent widths of the Ly and Si iii absorbers to be ∼1 and ∼0.4 Rvir, respectively. The radial distribution of equivalent widths is relatively uniform for the blue galaxies, but highly patchy (i.e., it has a low covering fraction) for the red galaxies. We also find that the Ly and Si iii equivalent widths show significant positive correlations with the specific star formation rate (sSFR) of the galaxy. We find a surprising lack of correlations between the halo mass (virial velocity) and either the velocity dispersions or velocity offsets of the Ly lines. The ratio of the velocity offset to the velocity dispersion for the Ly absorbers has a mean value of ∼4, suggesting that a given line of sight is intersecting a dynamically coherent structure in the CGM, rather than a sea of orbiting clouds. The kinematic properties of the CGM are similar in the blue and red galaxies, although we find that a significantly larger fraction of the blue galaxies have large Ly velocity offsets (>200 km s−1). We show that-if the CGM clouds represent future fuel for star formation-our new results could imply a large drop in the sSFR across the galaxy mass-range we probe.
ISSN:	0004-637X 1538-4357