The CGM² Survey: Circumgalactic O VI from Dwarf to Massive Star-forming Galaxies

Abstract

We combine 126 new galaxy-O VI absorber pairs from the CGM² survey with 123 pairs drawn from the literature to examine the simultaneous dependence of the column density of O VI absorbers (N _{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 _⊙ and galaxy-absorber impact parameters R _⊥ = 0-400 proper kiloparsecs. In this work, we focus on the variation of N _{O VI} with galaxy mass and impact parameter among the star-forming galaxies in the sample. We find that the average N _{O VI} within one virial radius of a star-forming galaxy is greatest for star-forming galaxies with M _* = 10^9.2-10¹⁰ M _⊙. Star-forming galaxies with M _* between 10⁸ and 10^11.2 M _⊙ can explain most O VI systems with column densities greater than 10^13.5 cm^-2. Sixty percent 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.