Circumgalactic Medium at High Halo Masses -- Signatures of Cold Gas Depletion in Luminous Red Galaxies (2310.11717v1)

Abstract: We study ultraviolet HI and metal line transitions in the circumgalactic medium (CGM) of 15 massive, quenched luminous red galaxies (LRGs) at redshift $z\sim 0.5$ and with impact parameters up to 400 kpc. We selected 8 of LRG-CGM systems to study general properties of the CGM around LRGs, while the other 7 are already known to contain cool CGM gas from MgII optical studies (MgII-LRGs). In the general LRGs population, we detect HI in 4 of 8 LRGs, in all cases with $N_{HI} < 10^{16.7} {\rm cm^{-2}}$. In contrast, all MgII-LRGs show HI; for four LRGs the HI column density is $N_{HI} \gtrsim 10^{18} {\rm cm^{-2}}$. The CGM of LRGs also shows low and intermediate ionized lines (such as CIII, CII, SiIII, SiII) and highly ionized lines of OVI (we detect OVI around 5 of 7 MgII-LRGs and 1 of 8 in the random sample). Next, we combine our sample with literature LRGs and $\lesssim L^{*}$ galaxies and we find that while for $\lesssim L^{*}$ galaxies CGM HI Ly$\alpha$ absorption is stronger as galaxies are more massive, the cool CGM traced by HI Ly$\alpha$ is suppressed above stellar masses of $M* \sim 10^{11.5}$ $M_{\odot}$. While most LRG CGM systems show weak or non-detectable OVI (equivalent width less than 0.2 \AA), a few LRG CGM systems show strong OVI 1031, which in most cases likely originates from groups containing both a LRG and a blue star-forming neighboring galaxy.