THE COS-HALOS SURVEY: PHYSICAL CONDITIONS AND BARYONIC MASS IN THE LOW-REDSHIFT CIRCUMGALACTIC MEDIUM

By Jessica Werk, J. Xavier Prochaska, Jason Tumlinson, Molly Peeples, T. Tripp, A. J. Fox, N. Lehner, C. Thom, John M. O’Meara, A. B. Ford and 6 more. 2014

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We analyze the physical conditions of the cool, photoionized (T ∼104 K) circumgalactic medium (CGM) using the COS-Halos suite of gas column density measurements for 44 gaseous halos within 160 kpc of L ∼ L* galaxies at z ∼ 0.2. These data are well described by simple photoionization models, with the gas highly ionized (nH ii/nH ≳ 99%) by the extragalactic ultraviolet background. Scaling by estimates for the virial radius, Rvir, we show that the ionization state (tracked by the dimensionless ionization parameter, U) increases with distance from the host galaxy. The ionization parameters imply a decreasing volume density profile nH = (10−4.2 ± 0.25)(R/Rvir)−0.8 ± 0.3. Our derived gas volume densities are several orders of magnitude lower than predictions from standard two-phase models with a cool medium in pressure equilibrium with a hot, coronal medium expected in virialized halos at this mass scale. Applying the ionization corrections to the H i column densities, we estimate a lower limit to the cool gas mass M☉ for the volume within R < Rvir. Allowing for an additional warm-hot, O vi-traced phase, the CGM accounts for at least half of the baryons purported to be missing from dark matter halos at the 1012 M☉ scale.

Subfields: Astronomy and Astrophysics, Instrumentation, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/9abb5acb796d42dd28cc1ff54ddf537978d1345a

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Citations in the corpus

Theoretical Challenges in Galaxy Formation (2016, background): “An even larger fraction (some of it hotter and ionised) gas might be stored in the so called ’circum galacitc medium’, the region extending from the star-forming interstellar medium into the galaxies halos (e.g. Somerville & Davé 2015, Werk et al. 2014).”
A Global Model for Circumgalactic and Cluster-core Precipitation (2016, background): “It should also apply to ambient circumgalactic gas near the virial temperature in lower-mass systems, in which the conditions can be probed by Hubble-COS observations (e.g., Stocke et al. 2013; Werk et al. 2014).”
Cosmological simulations of the circumgalactic medium with 1 kpc resolution: enhanced H i column densities (2018, background): “The large reservoirs of cool CGM detected in observations (e.g. Werk et al. 2014) arise naturally in cosmological simulations.”
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).”
The impact of star formation feedback on the circumgalactic medium (2016, background): “In Section 3.3 we present a comparison of our simulations to some of the key results that have come out of quasar absorption-line observations of the CGM in the z ∼ 0 universe (e.g., Tumlinson et al. 2011; Thom et al. 2012; Stocke et al. 2013; Werk et al. 2014; Borthakur et al. 2015).”
The Circumgalactic Medium (2017, methodology): “Hot gas at the virial temperature (Tvir= GMhalomp/kRvir) is a long-standing prediction.”
The COS-Halos Survey: Metallicities in the Low-redshift Circumgalactic Medium (2017, background): “Most galaxy-selected studies to date (Prochaska et al. 2011; Stocke et al. 2013; Borthakur et al. 2015; Werk et al. 2014, hereafter W14) have used small, heterogeneous samples dominated by systems bearing large NHI uncertainties caused by saturation in the Lyman series lines that yield lower limits…”
THE COS-HALOS SURVEY: ORIGINS OF THE HIGHLY IONIZED CIRCUMGALACTIC MEDIUM OF STAR-FORMING GALAXIES (2016, methodology): “More directly, Figure 3 presents a comparison between the predicted column densities of N ii and N iii for the systems using the photoionization models described by Werk et al. (2014) in which the CGM is ionized primarily by the extragalactic UV background (EUVB; Haardt & Madau 2001).”
THE COS-DWARFS SURVEY: THE CARBON RESERVOIR AROUND SUB-L* GALAXIES (2014, result): “Analysis of the lower ionization transitions further showed the presence of a large reservoir of metals and gas in the cool CGM (conservatively, TABLE 1 M INIMUM CARBON MASS ESTIMATES: Title logM∗/M⊙ Mcarbon/M⊙ a Mcarbon/M⊙ b 8 - 9.5 0.4× 106 0.4× 106 All galaxies 9.5 -10 0.9× 106 1.9× 106 8 - 9.5 0”
The Evolution of the Intergalactic Medium (2015, background): “…not cover the literature on damped Lyα systems (Wolfe, Gawiser & Prochaska 2005, which are primarily on the outskirts of galactic disks), on the intracluster medium (Rosati, Borgani & Norman 2002; Kravtsov & Borgani 2012), and on the circumgalactic medium (Stocke et al. 2013; Werk et al. 2014).”
Gusty, gaseous flows of FIRE: Galactic winds in cosmological simulations with explicit stellar feedback (2015, background): “…and beyond hints at a vast reservoir of gas that has been at least partially enriched with metals from galactic outflows (Chen et al. 1998; Chen, Lanzetta & Webb 2001; Gauthier, Chen & Tinker 2009; Kacprzak & Churchill 2011; Tumlinson et al. 2011; Werk et al. 2014; Lehner, Howk & Wakker 2015).”
A characteristic scale for cold gas (2016, background): “In particular, Werk et al. (2014) report very low densities for the cold gas in low-redshift galaxies (comparable to the expected density for the hot gas), along with high column densities of cold gas, NH ∼ 1020 cm−2.”
The cosmic baryon cycle and galaxy mass assembly in the FIRE simulations (2016, background): “Outflowing gas previously enriched in the interstellar medium (ISM) of galaxies must deposit heavy elements at large distances to explain the observed abundance of metals in the CGM (Tumlinson et al. 2011; Werk et al. 2014).”
An origin for multiphase gas in galactic winds and haloes (2015, background): “…of observations of systems including NGC 253 and M82, ultra-luminous infrared galaxies with high velocity line emission, high redshift rapidly star forming galaxies, and the absorption line systems both at z ∼ 0 observed by COS-Halos (Werk et al. 2014), and at high-redshift (Steidel et al. 2010).”
Cool outflows in galaxies and their implications (2020, background): “1 cm−3 for the Mg II CGM clouds (Prochaska et al. 2011; Kacprzak et al. 2014; Werk et al. 2014; Stern et al. 2016; Thompson et al. 2016; Zahedy et al. 2019), while nH ' 0.”