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  *~-M M 10 9.5 11.5, and over a range of impact parameters extending to just beyond the halo virial radius (R vir ). We find the radial scale length of the distributions of the equivalent widths of the Lyαand Si III absorbers to be ∼1 and ∼0.4R vir , 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 Lyα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 Lyαlines. The ratio of the velocity offset to the velocity dispersion for the Lyα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 Lyα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.

Ambient Column Densities of Highly Ionized Oxygen in Precipitation-limited Circumgalactic Media

“…In contrast, the precipitation interpretation simply requires the supernova energy to regulate the recycling rate through subsonic pressure-driven lifting of the CGM. The precipitation interpretation therefore appears to be in better alignment with observations showing that the speeds of CGM clouds are usually sub-Keplerian (e.g., Tumlinson et al 2011;Zhu et al 2014;Huang et al 2016;Borthakur et al 2016) and simulations showing that a large proportion of the baryons that end up in stars have cycled at least once through the CGM (Oppenheimer et al 2010;Anglés-Alcázar et al 2017).…”

The Impact of Enhanced Halo Resolution on the Simulated Circumgalactic Medium

“…Obser-chummels@gmail.com vations indicate the presence of cool 10 4 K CGM gas bearing neutral hydrogen and low ionization-potential ions ("low ions") like Mg II and Si II (e.g., Churchill et al 1996;Chen et al 1998;Steidel et al 2010;Gauthier et al 2010;Matejek & Simcoe 2012;Tumlinson et al 2013;Prochaska et al 2014;Werk et al 2014;Johnson et al 2017), as well as warmhot gas (10 5.5 -10 6 K) traced by "high ions" in the form of N V, O VI, and Ne VIII (e.g., Stocke et al 2006;Tumlinson et al 2011;Savage et al 2011;Tripp et al 2011;Meiring et al 2013;Pachat et al 2017;Burchett et al 2018). Observational studies consistently demonstrate large quantities and covering fractions for H I and other low ions in the CGM over many redshifts, environments, and halo masses (e.g., Rudie et al 2012, Borthakur et al 2016).…”

Hot Atmospheres, Cold Gas, AGN Feedback and the Evolution of Early Type Galaxies: A Topical Perspective

“…Other studies found similar absorbers in a significant fraction of LRG halos at projected distances d ≈ 100 − 500 kpc (Gauthier et al 2010;Huang et al 2016). Furthermore, strong Lyα absorption is common around z ≈ 0.2 early-type galaxies (Thom et al 2012;Tumlinson et al 2013), but at lower levels than in star forming galaxies (Borthakur et al 2016). However, using multiply-lensed QSOs, Zahedy et al (2017) found high column density gas around z = 0.4 − 0.7 ellipticals at projected distances as small as ≈ 3 − 15 kpc.…”