The COS-Halos Survey: Metallicities in the Low-Redshift Circumgalactic Medium

Abstract

We analyze new far-ultraviolet spectra of 13 quasars from the z~0.2 COS-Halos survey that cover the HI Lyman limit of 14 circumgalactic medium (CGM) systems. These data yield precise estimates or more constraining limits than previous COS-Halos measurements on the HI column densities NHI. We then apply a Monte-Carlo Markov Chain approach on 32 systems from COS-Halos to estimate the metallicity of the cool (T~10^4K) CGM gas that gives rise to low-ionization state metal lines, under the assumption of photoionization equilibrium with the extragalactic UV background. The principle results are: (1) the CGM of field L* galaxies exhibits a declining HI surface density with impact parameter Rperp (at >99.5%$ confidence), (2) the transmission of ionizing radiation through CGM gas alone is 70+/-7%; (3) the metallicity distribution function of the cool CGM is unimodal with a median of 1/3 Z_Sun and a 95% interval from ~1/50 Z_Sun to over 3x solar. The incidence of metal poor (<1/100 Z_Sun) gas is low, implying any such gas discovered along quasar sightlines is typically unrelated to L* galaxies; (4) we find an unexpected increase in gas metallicity with declining NHI (at >99.9% confidence) and, therefore, also with increasing Rperp. The high metallicity at large radii implies early enrichment; (5) A non-parametric estimate of the cool CGM gas mass is M_CGM_cool = 9.2 +/- 4.3 10^10 Msun, which together with new mass estimates for the hot CGM may resolve the galactic missing baryons problem. Future analyses of halo gas should focus on the underlying astrophysics governing the CGM, rather than processes that simply expel the medium from the halo.

26 pages with figures. Accepted to ApJ; see https://github.com/pyigm/pyigm for all published COS-Halos measurements

References in corpus (22)

• The COS-Halos Survey: Physical Conditions and Baryonic Mass in the Low-Redshift Circumgalactic Medium
• Time-Dependent Ionization in Radiatively Cooling Gas
• Images, structural properties and metal abundances of galaxy clusters observed with Chandra ACIS-I at 0.1<z<1.3
• Characterizing the Circumgalactic Medium of Nearby Galaxies with HST/COS and HST/STIS Absorption-Line Spectroscopy
• The COS-Dwarfs Survey: The Carbon Reservoir Around sub-L* Galaxies
• Do Hot Haloes Around Galaxies Contain the Missing Baryons?
• The COS-Halos Survey: Origins of the Highly Ionized Circumgalactic Medium of Star-Forming Galaxies
• A Local Clue to the Reionization of the Universe
• Distances to Galactic high-velocity clouds. I. Cohen Stream, complex GCP, cloud g1
• Metal-line absorption around $z\approx$2.4 star-forming galaxies in the Keck Baryonic Structure Survey
• On the possible environmental effect in distributing heavy elements beyond individual gaseous halos
• A large population of metal-rich, compact, intergalactic C IV absorbers - Evidence for poor small-scale metal mixing
• An Accurate Distance to High-Velocity Cloud Complex C
• Metal-enriched, sub-kiloparsec gas clumps in the circumgalactic medium of a faint z = 2.5 galaxy
• Evidence for a Massive, Extended Circumgalactic Medium Around the Andromeda Galaxy
• The Photon Underproduction Crisis
• The Enrichment History of Baryons in the Universe
• A Survey of O VI, C III, and H I in Highly Ionized High-Velocity Clouds
• Metallicity and Ionization in High Velocity Cloud Complex C
• XMM-Newton Survey of Local O VII Absorption Lines in the Spectra of Active Galactic Nuclei
• Low-metallicity Absorbers Account for Half of the Dense Circumgalactic Gas at z < 1
• Probing the IGM/Galaxy Connection Toward PKS0405-123 III: The Galaxy Survey and Correlations with OVI Absorbers

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