The survival of gas clouds in the circumgalactic medium of Milky Way-like galaxies
Date
2017
Authors
Armillotta, Lucia
Fraternali, F
Werk, J K
Prochaska, J. Xavier
Marinacci, F
Journal Title
Journal ISSN
Volume Title
Publisher
Oxford University Press
Abstract
Observational evidence shows that low-redshift galaxies are surrounded by extended haloes of
multiphase gas, the so-called circumgalactic medium (CGM). To study the survival of relatively
cool gas (T < 105 K) in the CGM, we performed a set of hydrodynamical simulations of cold (T = 104 K) neutral gas clouds travelling through a hot (T = 2 × 106 K) and low-density (n = 10−4 cm−3) coronal medium, typical of Milky Way-like galaxies at large galactocentric distances (∼50–150 kpc).We explored the effects of different initial values of relative velocity and radius of the clouds. Our simulations were performed on a two-dimensional grid with constant mesh size (2 pc), and they include radiative cooling, photoionization heating and thermal conduction. We found that for large clouds (radii larger than 250 pc), the cool gas survives for very long time (larger than 250 Myr): despite that they are partially destroyed and fragmented into smaller cloudlets during their trajectory, the total mass of cool gas decreases at very low rates. We found that thermal conduction plays a significant role: its effect is to hinder formation of hydrodynamical instabilities at the cloud–corona interface, keeping the cloud compact and therefore more difficult to destroy. The distribution of column densities extracted from our simulations is compatible with those observed for low-temperature ions (e.g. Si II and Si III) and for high-temperature ions (O VI) once we take into account that OVI covers much more extended regions than the cool gas and, therefore, it is more likely to be detected along a generic line of sight.
Description
Keywords
conduction, hydrodynamics, methods: numerical, galaxies: haloes, intergalactic medium
Citation
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Source
Monthly Notices of the Royal Astronomical Society
Type
Journal article
Book Title
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Access Statement
Open Access