Cosmic Ray Driven Outflows in an Ultraluminous Galaxy

Abstract

In models of galaxy formation, feedback driven both by supernova (SN) and active galactic nucleus (AGN) is not efficient enough to quench star formation in massive galaxies. Models of smaller galaxies have suggested that cosmic rays (CRs) play a major role in expelling material from the star forming regions by diffusing SN energy to the lower density outskirts. We therefore run gas dynamical simulations of galactic outflows from a galaxy contained in a halo with $5\times 10^{12}$~M${}_{\odot }$ that resembles a local ultraluminous galaxy, including both SN thermal energy and a treatment of CRs using the same diffusion approximation as Salem & Bryan. We find that CR pressure drives a low-density bubble beyond the edge of the shell swept up by thermal pressure, but the main bubble driven by SN thermal pressure overtakes it later, which creates a large-scale biconical outflow. CRs diffusing into the disk are unable to entrain its gas in the outflows, yielding a mass-loading rate of only $\sim 0.1\%$ with varied CR diffusion coefficients. We find no significant difference in mass-loading rates in SN driven outflows with or without CR pressure. Our simulations strongly suggest that it is hard to drive a heavily mass-loaded outflow with CRs from a massive halo potential, although more distributed star formation could lead to a different result.

MNRAS 477, 531-538 (2018) published in 2018 March 17

References in corpus (5)

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• A connection between star formation activity and cosmic rays in the starburst galaxy M 82
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• A hydrodynamical study of outflows in starburst galaxies with different driving mechanisms
• Role of cosmic rays in the early stages of galactic outflows
• Cosmic ray driven galactic winds
• The angular momentum structure of cosmic ray driven galactic outflows triggered by stream accretion
• Column Density Profiles of Cold Clouds Driven by Galactic Outflows
• Dust in Clusters of Galaxies
• Radio halos of star forming galaxies
• Exploring the Voids: Luminosity Functions and Magnetic Field