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

By J. Xavier Prochaska, Jessica Werk, G. Worseck, T. Tripp, Jason Tumlinson, Joseph Fox, M. Fumagalli, N. Lehner, Molly Peeples, Nicolas Tejos Uco and 11 more. 2017

217 citations recorded by the source corpus.

We analyze new far-ultraviolet spectra of 13 quasars from the COS-Halos survey that cover the H i Lyman limit of 14 circumgalactic medium (CGM) systems. These data yield precise estimates or more constraining limits than previous COS-Halos measurements on the H i column densities . We then apply a Monte-Carlo Markov chain approach on 32 systems from COS-Halos to estimate the metallicity of the cool ( K) 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 H i surface density with impact parameter (at 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 and a 95% interval to ; the incidence of metal-poor ( ) 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 (at confidence) and, therefore, also with increasing ; the high metallicity at large radii implies early enrichment; and (5) a non-parametric estimate of the cool CGM gas mass is , 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.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/fc8e325e7d0e1bc581ece91c2bb2bb427de822d1

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Citations in the corpus

Probing Galactic Halos with Fast Radio Bursts (2019, methodology): “…constrain the ionization model and thereby infer NH. Figure 13 shows a reproduction of the NH probability distribution function (PDF) – as a function of radial bins – derived from the COS-Halos survey by Prochaska et al. (2017), expressed as DM values assuming the µe = 1.167 correction for Helium.”
Cosmological simulations of the circumgalactic medium with 1 kpc resolution: enhanced H i column densities (2018, background): “The vertical dotted, grey line indicates the minimum column density for LLSs (NH I ≥ 1017.2 cm−2) and the black error bars show the covering fractions in the COS-Halos survey (Tumlinson et al. 2013; Prochaska et al. 2017).”
The Circumgalactic Medium (2017, methodology): “In contrast to the Lehner bimodality, Prochaska et al. (2017) find a unimodal distribution of metallicities within 160 kpc of L* galaxies with a median of ∼ 30% solar.”
Figuring Out Gas & Galaxies in Enzo (FOGGIE). I. Resolving Simulated Circumgalactic Absorption at 2 ≤ z ≤ 2.5 (2018, background): “In the galactic ecosystem, the majority of baryons and heavy elements are in the diffuse gas outside of galaxies rather than in the relatively dense gas and stars composing the disks and central spheroids (Pagel 2008; Stocke et al. 2013; Peeples et al. 2014; Werk et al. 2014; Prochaska et al. 2017).”