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تسجيل مستخدم جديدThe Red Dead Redemption Survey of Circumgalactic Gas About Massive Galaxies. I. Mass and Metallicity of the Cool Phase
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تأليف
Michelle A. Berg
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We present a search for HI in the circumgalactic medium (CGM) of 21 massive ($langle log M_star rangle sim 11.4$), luminous red galaxies (LRGs) at $zsim0.5$. Using UV spectroscopy of QSO sightlines projected within 500 kpc ($sim R_{vir}$) of these galaxies, we detect HI absorption in 11/21 sightlines, including two partial Lyman limit systems and two Lyman limit systems. The covering factor of $log N(HI) ge 16.0$ gas within the virial radius of these LRGs is $f_c(rho le R_{vir}) = 0.27^{+0.11}_{-0.10}$, while for optically-thick gas ($log N(HI) ge 17.2$) it is $f_c(rho le R_{vir}) = 0.15^{+0.10}_{-0.07}$. Combining this sample of massive galaxies with previous galaxy-selected CGM studies, we find no strong dependence of the HI 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 $9.5 lesssim log M_star lesssim 11.8$). The metallicity distribution in LRGs is indistinguishable from those found about lower-mass star-forming galaxies, and we find low-metallicity gas with $[{rm X/H}] approx -1.8$ (1.5% solar) and below about massive galaxies. About half the cases show super-solar [FeII/MgII] 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.
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