MUSEQuBES: Probing Anisotropies in Gas and Metal Distributions in the Circumgalactic Medium

Abstract

We investigate the azimuthal dependence of HI and OVI-bearing gas in the circumgalactic medium (CGM) of 113 isolated galaxies in the redshift range $0.12<z<0.75$, including 91 new measurements from the MUSE Quasar-fields Blind Emitters Survey (MUSEQuBES). Of these, measurements for 46 galaxies lie within the virial radius ($R_{\mathrm{vir}}$), including 36 non-face-on systems for which azimuthal angle ($\varphi$) measurements are robust. The HI covering fraction (k_HI) within $R_{\mathrm{vir}}$ of low-mass ($7<\log (M/M_{\odot })\le 9$) galaxies, for a threshold column density of ${\log }_{10}(N(HI)/{\mathrm{cm}}^{-2})=14.5$, exhibits an enhancement along both the disk plane ($\varphi \lesssim 20^{\circ }$) and in the polar direction ($\varphi \gtrsim 70^{\circ }$). In contrast, such a bimodal distribution is not observed for higher mass galaxies ($9<\log (M/M_{\odot })\le 11.3$). Similarly, the OVI covering fraction (k_OVI), for a threshold of ${\log }_{10}(N(OVI)/{\mathrm{cm}}^{-2})=14.0$, shows a tentative enhancement along both the projected major and minor axes for low-mass galaxies. In contrast, \OVI-bearing gas around higher-mass galaxies appears more uniformly distributed, with no significant azimuthal dependence. Finally, using the halo circular-velocity-normalized pixel-velocity two-point correlation function (TPCF), we find that OVI absorbers are kinematically narrower along the disk plane compared to the polar directions of the host galaxies with similar stellar mass distributions. The observed isotropic distribution of OVI in high-mass halos suggests that its spatial distribution is governed by global halo properties; however, the OVI kinematics retain memory of the site of origin.

Accepted for publication in ApJ