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

TL;DR

This study develops an automated pipeline to analyze SDSS DR16 data, revealing how the cool circumgalactic medium's properties and distribution vary around different galaxy types and with galaxy characteristics.

Contribution

It introduces a large-scale analysis of MgII and FeII absorbers around galaxies, providing new insights into the CGM's scale dependence and its relation to galaxy type and star formation.

Findings

MgII absorption is enhanced within 50 kpc of emission line galaxies.

Covering fraction within 0.5 virial radius is 2-5 times higher for ELGs than LRGs.

The CGM's physical origin differs between star-forming and quiescent galaxies.

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 $\sim$ one million quasars in the latest Data Release 16 (DR16) of the Sloan Digital Sky Survey (SDSS) and compile a large sample of $\sim$ 160,000 MgII absorbers, together with $\sim$ 70,000 FeII systems, in the redshift range $0.35<z_{abs}<2.3$. Combining these with the SDSS DR16 spectroscopy of $\sim1.1$ million luminous red galaxies (LRGs) and $\sim 200,000$ 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 MgII with greater accuracy than in previous work. We find that there is a strong enhancement of MgII absorption within $\sim 50$ kpc of ELGs, and the covering fraction within $0.5r_{\rm vir}$ of ELGs is 2-5 times higher than for LRGs. Beyond 50 kpc, there is a sharp decline in MgII for both kinds of galaxies, indicating a transition to the regime where the CGM is tightly linked with the dark matter halo. The MgII 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.