Characterizing the abundance, properties, and kinematics of the cool circumgalactic medium of galaxies in absorption with SDSS DR16

Abstract

In order to study the circumgalactic medium (CGM) of galaxies we develop an automated pipeline to estimate the optical continuum of quasars and detect intervening metal absorption line systems with a matched kernel convolution technique and adaptive S/N criteria. We process ∼ one million quasars in the latest Data Release 16 (DR16) of the Sloan Digital Sky Survey (SDSS) and compile a large sample of ∼ 160,000 Mg ii absorbers, together with ∼ 70,000 Fe ii systems, in the redshift range 0.35 < zabs < 2.3. Combining these with the SDSS DR16 spectroscopy of ∼1.1 million luminous red galaxies (LRGs) and ∼200, 000 emission line galaxies (ELGs), we investigate the nature of cold gas absorption at 0.5 < z < 1. These large samples allow us to characterize the scale dependence of Mg ii with greater accuracy than in previous work. We find that there is a strong enhancement of Mg ii absorption within ∼50 kpc of ELGs, and the covering fraction within 0.5rvir of ELGs is 2-5 times higher than for LRGs. Beyond 50 kpc, there is a sharp decline in Mg ii for both kinds of galaxies, indicating a transition to the regime where the CGM is tightly linked with the dark matter halo. The Mg ii covering fraction correlates strongly with stellar mass for LRGs, but weakly for ELGs, where covering fractions increase with star formation rate. Our analysis implies that cool circumgalactic gas has a different physical origin for star forming versus quiescent galaxies.

How are Lyman $α$ absorbers in the cosmic web related to gas-rich galaxies?

“…A comparison of the CGM between blue star-forming and red quiescent galaxies with stellar masses, log M ∼ 9.5 − 11.5 from the COS-GASS (Borthakur et al 2015) and COS-Halos (Werk et al 2014) surveys revealed that the covering fraction of neutral circumgalactic gas as traced by Lyman α absorbers is ≈100% in blue star-forming galaxies, but lower for red quiescent galaxies . Similar differences in Mg II covering fraction is also seen between red and blue galaxies (Anand et al 2021). The redshift evolution of cool gas content of the CGM is also found to be consistent with the starformation rate of the host galaxies (Lan 2020).…”

Improving Physical Cosmology: An Empiricist's Assessment

“…At smaller distances, < ∼ 50 kpc, there is considerably more cool gas around late types, as in emission line galaxies. Perhaps this is related to the feeding of, or the winds from, the greater star formation rate among late type galaxies [110,111,112]. Might it be a hint to the bistability discussed in Topic 13d?…”

Cooling flows around cold clouds in the circumgalactic medium: steady-state models & comparison with TNG50

“…Here we compare our cooling flow model against the properties of cold clouds within halos in a cosmological MHD simulation. In particular, we assess the structure and cooling properties of small (∼kpc) cold clouds found to populate high-mass halos by the thousands (Nelson et al 2020), similar to the inferred large abundance of cold gas surrounding luminous red galaxies (LRGs) in SDSS (Anand et al 2021). Nelson et al (2020) concluded that the cool phase of the CGM resulted from cooling on to dense, cold 'seeds' of gas primarily produced due to the strong density perturbations of satellite galaxies.…”