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arXiv · 1804.00741

Fast Winds Drive Slow Shells: A Model for the Circumgalactic Medium as Galactic Wind-Driven Bubbles

Cassandra Lochhaas·Todd A. Thompson·Eliot Quataert·David H. Weinberg
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Abstract

Successful models of the low redshift circumgalactic medium (CGM) must account for (1) a large amount of gas, (2) relatively slow gas velocities, (3) a high degree of metal enrichment, (4) the similar absorption properties around both star-forming and passive galaxies, and (5) the observationally inferred temperature and densities of the CGM gas. We show that galactic wind-driven bubbles can account for these observed properties. We develop a model describing the motion of bubbles driven by a hot, fast galactic wind characteristic of supernova energy injection. The bubble size grows slowly to hundreds of kiloparsecs over $5-10$ Gyr. For high star formation rates or high wind mass loading $\dot M_w/\dot M_\star$, the free-flowing hot wind, the shocked hot wind in the interior of the bubble, and the swept-up halo gas within the bubble shell can all radiatively cool and contribute to low-ionization state metal line absorption. We verify that if the free-flowing wind cools, the shocked wind does as well. We find effective mass loading factors of $(M_w+M_\mathrm{swept})/M_\star\sim5-12$ as the bubbles sweep into the CGM. We predict cool gas masses, velocities, column densities, metal content, and absorption line velocities and linewidths of the bubble for a range of parameter choices. This picture can reproduce many of the COS-Halos and Keeney et al. (2017) observations of low-ionization state metal absorption lines around both star-forming and passive galaxies.

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Cassandra Lochhaas, Todd A. Thompson, Eliot Quataert, David H. Weinberg. 2018-09-03. Fast Winds Drive Slow Shells: A Model for the Circumgalactic Medium as Galactic Wind-Driven Bubbles. https://doi.org/10.1093/mnras%2Fsty2421

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