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

K. Tchernyshyov, J. K. Werk, M. C. Wilde, J. X. Prochaska, T. M. Tripp, J. N. Burchett, R. Bordoloi, J. C. Howk, N. Lehner, J. M. O'Meara, N. Tejos, J. Tumlinson

Published 2021-10-25, updated 2021-12-21Version 2

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.