Implications of the large OVI columns around low-redshift $L_{\ast }$ galaxies

Abstract

Observations reveal massive amounts of OVI around star-forming $L_{\ast }$ galaxies, with covering fractions of near unity extending to the host halo's virial radius. This OVI absorption is typically kinematically centered upon photoionized gas, with line widths that are suprathermal and kinematically offset from the galaxy. We discuss various scenarios and whether they could result in the observed phenomenology (cooling gas flows, boundary layers, shocks, virialized gas, photoionized clouds in thermal equilibrium). If predominantly collisionally ionized, as we argue is most probable, the OVI observations require that the circumgalactic medium (CGM) of $L_{\ast }$ galaxies holds nearly all the associated baryons within a virial radius ($\sim 10^{11}{M}_{\odot }$) and hosts massive flows of cooling gas with $\approx 30[nT/30\mathrm{c}{\mathrm{m}}^{-3}\mathrm{K}]M_{\odot }$yr${}^{-1}$, which must be largely prevented from accreting onto the host galaxy. Cooling and feedback energetics considerations require $10<⟨nT⟩<100\mathrm{c}{\mathrm{m}}^{-3}\mathrm{K}$ for the warm and hot halo gases. We argue that virialized gas, boundary layers, hot winds, and shocks are unlikely to directly account for the bulk of the OVI. Furthermore, we show that there is a robust constraint on the number density of many of the photoionized $\sim 10^4$K absorption systems that yields upper bounds in the range $n<(0.1-3)\times 10^{-3}(Z/0.3)$cm${}^{-3}$, where $Z$ is the metallicity, suggestive that the dominant pressure in some photoionized clouds is nonthermal. This constraint, which requires minimal ionization modeling, is in accord with the low densities inferred from more complex photoionization modeling. The large amount of cooling gas that is inferred could re-form these clouds in a fraction of the halo dynamical time, as some arguments require, and it requires much of the feedback energy available from supernovae and stellar winds to be dissipated in the CGM.

16 pages, matches version accepted to ApJ

References in corpus (18)

• The effect of photo-ionization on the cooling rates of enriched, astrophysical plasmas
• The COS-Halos Survey: Physical Conditions and Baryonic Mass in the Low-Redshift Circumgalactic Medium
• Time-Dependent Ionization in Radiatively Cooling Gas
• The COS-Halos Survey: Metallicities in the Low-Redshift Circumgalactic Medium
• Characterizing the Circumgalactic Medium of Nearby Galaxies with HST/COS and HST/STIS Absorption-Line Spectroscopy
• Constraining the Milky Way's Hot Gas Halo with OVII and OVII Emission Lines
• Magnetized Gas Clouds can Survive Acceleration by a Hot Wind
• Raining on black holes and massive galaxies: the top-down multiphase condensation model
• The COS-Halos Survey: Origins of the Highly Ionized Circumgalactic Medium of Star-Forming Galaxies
• The Impact of Star Formation Feedback on the Circumgalactic Medium
• On the possible environmental effect in distributing heavy elements beyond individual gaseous halos
• An HST/COS legacy survey of high-velocity ultraviolet absorption in the Milky Way's circumgalactic medium and the Local Group
• A Universal Density Structure for Circum-Galactic Gas
• Discovery of 14 radio pulsars in a survey of the Magellanic Clouds
• Numerical Study of Turbulent Mixing Layers with Non-Equilibrium Ionization Calculations
• Intergalactic Lyman continuum photon budget in the past 5 billion years
• The formation and physical origin of highly ionized cooling gas
• Constraints on galactic wind models

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