We present a search for \ion H1 in the circumgalactic medium ( CGM ) of 21 massive ( \langle \log M _ { \star } \rangle \sim 11.4 ) , luminous red galaxies ( LRGs ) at z \sim 0.5 .
Using UV spectroscopy of QSO sightlines projected within 500 kpc ( \sim R _ { vir } ) of these galaxies , we detect \ion H1 absorption in 11/21 sightlines , including two partial Lyman limit systems and two Lyman limit systems .
The covering factor of \log N ( \mbox { \ion { H } { 1 } } ) \geq 16.0 gas within the virial radius of these LRGs is f _ { c } ( \rho \leq R _ { vir } ) = 0.27 ^ { +0.11 } _ { -0.10 } , while for optically-thick gas ( \log N ( \mbox { \ion { H } { 1 } } ) \geq 17.2 ) it is f _ { c } ( \rho \leq R _ { vir } ) = 0.15 ^ { +0.10 } _ { -0.07 } .
Combining this sample of massive galaxies with previous galaxy-selected CGM studies , we find no strong dependence of the \ion H1 covering factor on galaxy mass , although star-forming galaxies show marginally higher covering factors .
There is no evidence for a critical mass above which dense , cold ( T \sim 10 ^ { 4 } K ) gas is suppressed in the CGM of galaxies ( spanning stellar masses 9.5 \la \log M _ { \star } \la 11.8 ) .
The metallicity distribution in LRGs is indistinguishable from those found about lower-mass star-forming galaxies , and we find low-metallicity gas with [ { X / H } ] \approx - 1.8 ( 1.5 % solar ) and below about massive galaxies . \added About half the cases show super-solar [ \ion Fe2 / \ion Mg2 ] abundances as seen previously in cool gas near massive galaxies .
While the high-metallicity cold gas seen in LRGs could plausibly result from condensation from a corona , the low-metallicity gas is inconsistent with this interpretation .