The CGM$^2$ Survey: Circumgalactic O VI from dwarf to massive star-forming galaxies

TL;DR

This study combines new and literature data to analyze how O VI absorption in the circumgalactic medium varies with galaxy mass and impact parameter, revealing mass-dependent trends and the need for non-hydrostatic models.

Contribution

It provides the first comprehensive analysis of O VI in the CGM across a wide galaxy mass range, highlighting the mass dependence and spatial extent of O VI absorption.

Findings

Maximum $N_{O VI}$ occurs in galaxies with $10^{9.2}$-$10^{10}$ $M_ ext{sun}$.

Most O VI mass is within one virial radius of the galaxy.

Departure from hydrostatic equilibrium is needed to explain observations.

Abstract

We combine 126 new galaxy-O VI absorber pairs from the CGM$^2$ survey with 123 pairs drawn from the literature to examine the simultaneous dependence of the column density of O VI absorbers ($N_{\rm O VI}$) on galaxy stellar mass, star formation rate, and impact parameter. The combined sample consists of 249 galaxy-O VI absorber pairs covering $z=0$-$0.6$, with host galaxy stellar masses $M^*=10^{7.8}$-$10^{11.2}$ $M_\odot$ and galaxy-absorber impact parameters $R_\perp=0$-$400$ proper kiloparsecs. In this work, we focus on the variation of $N_{\rm O VI}$ with galaxy mass and impact parameter among the star-forming galaxies in the sample. We find that the average $N_{\rm O VI}$ within one virial radius of a star-forming galaxy is greatest for star-forming galaxies with $M^*=10^{9.2}$-$10^{10}$ $M_\odot$. Star-forming galaxies with $M^*$ between $10^{8}$ and $10^{11.2}$ $M_\odot$ can explain most O VI systems with column densities greater than 10$^{13.5}$ cm$^{-2}$. 60% of the O VI mass associated with a star-forming galaxy is found within one virial radius and 35% is found between one and two virial radii. In general, we find that some departure from hydrostatic equilibrium in the CGM is necessary to reproduce the observed O VI amount, galaxy mass dependence, and extent. Our measurements serve as a test set for CGM models over a broad range of host galaxy masses.