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Properties of gas in and around galaxy haloes

van de Voort, Freeke ORCID: and Schaye, Joop 2012. Properties of gas in and around galaxy haloes. Monthly Notices of the Royal Astronomical Society 423 (4) , pp. 2991-3010. 10.1111/j.1365-2966.2012.20949.x

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We study the properties of gas inside and around galaxy haloes as a function of radius and halo mass, focusing mostly on z= 2, but also showing some results for z= 0. For this purpose, we use a suite of large cosmological, hydrodynamical simulations from the OverWhelmingly Large Simulations project. The properties of cold- and hot-mode gas, which we separate depending on whether the temperature has been higher than 105.5 K while it was extragalactic, are clearly distinguishable in the outer parts of massive haloes (virial temperatures ≫105 K). The differences between cold- and hot-mode gas resemble those between inflowing and outflowing gas. The cold-mode gas is mostly confined to clumpy filaments that are approximately in pressure equilibrium with the diffuse, hot-mode gas. Besides being colder and denser, cold-mode gas typically has a much lower metallicity and is much more likely to be infalling. However, the spread in the properties of the gas is large, even for a given mode and a fixed radius and halo mass, which makes it impossible to make strong statements about individual gas clouds. Metal-line cooling causes a strong cooling flow near the central galaxy, which makes it hard to distinguish gas accreted through the cold and hot modes in the inner halo. Stronger feedback results in larger outflow velocities and pushes hot-mode gas to larger radii. The gas properties evolve as expected from virial arguments, which can also account for the dependence of many gas properties on halo mass. We argue that cold streams penetrating hot haloes are observable as high column density H i Lyman α absorption systems in sightlines near massive foreground galaxies.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Publisher: Oxford University Press
ISSN: 0035-8711
Date of First Compliant Deposit: 12 March 2020
Date of Acceptance: 15 March 2012
Last Modified: 05 May 2023 12:00

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