2020/02/29 by Philip F. Hopkins, T. K. Chan, T K Chan +7 · 1 citation
Physics and Astronomy · #Astrophysics #Astrophysics and Cosmic Phenomena #Astrophysics and Star Formation Studies #Galaxies: Formation, Evolution, Phenomena #Galaxy #Halo #Outflow #Physics #Radiation pressure #Ram pressure #Redshift #Star formation #Supernova #astro-ph.CO #astro-ph.GA #astro-ph.HE
paper · pdf · doi:10.1093/mnras/staa3690
published as MNRAS, 2021, 501, 3 · 24 pages, 20 figures, revised to match published MNRAS version. Comments welcome. Animations in CGM/IGM section at http://www.tapir.caltech.edu/~phopkins/Site/animations/
openalex publication_date 2020/11/27 · openalex created_date 2020/12/07 · arxiv created 2022/03/16 · arxiv updated 2022/03/18 · openalex updated_date 2026/08/06
We study the effects of cosmic rays (CRs) on outflows from star-forming galaxies in the circum and inter-galactic medium (CGM/IGM), in high-resolution, fully-cosmological FIRE-2 simulations (accounting for mechanical and radiative stellar feedback, magnetic fields, anisotropic conduction/viscosity/CR diffusion and streaming, and CR losses). We showed previously that massive (M\rm halo\gtrsim 1011 M\odot), low-redshift (z\lesssim 1-2) halos can have CR pressure dominate over thermal CGM pressure and balance gravity, giving rise to a cooler CGM with an equilibrium density profile. This dramatically alters outflows. Absent CRs, high gas thermal pressure in massive halos "traps" galactic outflows near the disk, so they recycle. With CRs injected in supernovae as modeled here, the low-pressure halo allows "escape" and CR pressure gradients continuously accelerate this material well into the IGM in "fast" outflows, while lower-density gas at large radii is accelerated in-situ into "slow" outflows that extend to >Mpc scales. CGM/IGM outflow morphologies are radically altered: they become mostly volume-filling (with inflow in a thin mid-plane layer) and coherently biconical from the disk to >Mpc. The CR-driven outflows are primarily cool (T∼105 K) and low-velocity. All of these effects weaken and eventually vanish at lower halo masses (\lesssim 1011 M\odot) or higher redshifts (z\gtrsim 1-2), reflecting the ratio of CR to thermal+gravitational pressure in the outer halo. We present a simple analytic model which explains all of the above phenomena.