We present a study of extended galaxy halo gas through H I and O VI absorption over two decades in projected distance at z ≈ 0.2. The study is based on a sample of 95 galaxies from a highly complete (> 80%) survey of faint galaxies (L > 0.1L * ) with archival quasar absorption spectra and 53 galaxies from the literature. A clear anti-correlation is found between H I (O VI) column density and virial radius normalized projected distance, d/R h . Strong H I (O VI) absorption systems with column densities greater than 10 14.0 (10 13.5 ) cm −2 are found for 48 of 54 (36 of 42) galaxies at d < R h indicating a mean covering fraction of κ H I = 0.89 ( κ O VI = 0.86). O VI absorbers are found at d ≈ R h , beyond the extent observed for lower ionization species. At d/R h = 1 − 3 strong H I (O VI) absorption systems are found for only 7 of 43 (5 of 34) galaxies ( κ H I = 0.16 and κ O VI = 0.15). Beyond d = 3 R h , the H I and O VI covering fractions decrease to levels consistent with coincidental systems.The high completeness of the galaxy survey enables an investigation of environmental dependence of extended gas properties. Galaxies with nearby neighbors exhibit a modest increase in O VI covering fraction at d > R h compared to isolated galaxies (κ OVI ≈ 0.13 versus 0.04) but no excess H I absorption. These findings suggest that environmental effects play a role in distributing heavy elements beyond the enriched gaseous halos of individual galaxies. Finally, we find that differential H I and O VI absorption between early-and late-type galaxies continues from d < R h to d ≈ 3 R h .

We present a systematic investigation of the circumgalactic medium (CGM) within projected distances d < 160 kpc of luminous red galaxies (LRGs). The sample comprises 16 intermediate-redshift (z = 0.21−0.55) LRGs of stellar mass M star > 10 11 M . Combining far-ultraviolet Cosmic Origin Spectrograph spectra from the Hubble Space Telescope and optical echelle spectra from the ground enables a detailed ionization analysis based on resolved component structures of a suite of absorption transitions, including the full H i Lyman series and various ionic metal transitions. By comparing the relative abundances of different ions in individually-matched components, we show that cool gas (T ∼ 10 4 K) density and metallicity can vary by more than a factor of ten in an LRG halo. Specifically, metal-poor absorbing components with < 1/10 solar metallicity are seen in 50% of the LRG halos, while gas with solar and super-solar metallicity is also common. These results indicate a complex multiphase structure and poor chemical mixing in these quiescent halos. We calculate the total surface mass density of cool gas, Σ cool , by applying the estimated ionization fraction corrections to the observed H i column densities. The radial profile of Σ cool is best-described by a projected Einasto profile of slope α = 1 and scale radius r s = 48 kpc. We find that typical LRGs at z ∼ 0.4 contain cool gas mass of M cool = (1 − 2) × 10 10 M at d < 160 kpc (or as much as M cool ≈ 4 × 10 10 M at d < 500 kpc), comparable to the cool CGM mass of star-forming galaxies. Furthermore, we show that high-ionization O vi and low-ionization absorption species exhibit distinct velocity profiles, highlighting their different physical origins. We discuss the implications of our findings for the origin and fate of cool gas in LRG halos.

We carry out a comprehensive Bayesian correlation analysis between hot halos and direct masses of supermassive black holes (SMBHs), by retrieving the X-ray plasma properties (temperature, luminosity, density, pressure, masses) over galactic to cluster scales for 85 diverse systems. We find new key scalings, with the tightest relation being the M • − T x , followed by M • − L x . The tighter scatter (down to 0.2 dex) and stronger correlation coefficient of all the X-ray halo scalings compared with the optical counterparts (as the M • − σ e ) suggest that plasma halos play a more central role than stars in tracing and growing SMBHs (especially those that are ultramassive). Moreover, M • correlates better with the gas mass than dark matter mass. We show the important role of the environment, morphology, and relic galaxies/coronae, as well as the main departures from virialization/self-similarity via the optical/X-ray fundamental planes. We test the three major channels for SMBH growth: hot/Bondilike models have inconsistent anti-correlation with X-ray halos and too low feeding; cosmological simulations find SMBH mergers as sub-dominant over most of the cosmic time and too rare to induce a central-limit-theorem effect; the scalings are consistent with chaotic cold accretion (CCA), the rain of matter condensing out of the turbulent X-ray halos that sustains a long-term self-regulated feedback loop. The new correlations are major observational constraints for models of SMBH feeding/feedback in galaxies, groups, and clusters (e.g., to test cosmological hydrodynamical simulations), and enable the study of SMBHs not only through X-rays, but also via the Sunyaev-Zel'dovich effect (Compton parameter), lensing (total masses), and cosmology (gas fractions).