Cosmic ray driven outflows in global galaxy disc models

By Munier Salem, Greg L. Bryan. 2013

163 citations recorded by the source corpus.

Galactic-scale winds are a generic feature of massive galaxies with high star formation rates across a broad range of redshifts. Despite their importance, a detailed physical understanding of what drives these mass-loaded global flows has remained elusive. In this paper, we explore the dynamical impact of cosmic rays by performing the first three-dimensional, adaptive mesh refinement simulations of an isolated starbursting galaxy that includes a basic model for the production, dynamics and diffusion of galactic cosmic rays. We find that including cosmic rays naturally leads to robust, massive, bipolar outflows from our 10^12 Msun halo, with a mass-loading factor Mout/SFR = 0.3 for our fiducial run. Other reasonable parameter choices led to mass-loading factors above unity. The wind is multiphase and is accelerated to velocities well in excess of the escape velocity. We employ a two-fluid model for the thermal gas and relativistic CR plasma and model a range of physics relevant to galaxy formation, including radiative cooling, shocks, self-gravity, star formation, supernovae feedback into both the thermal and CR gas, and isotropic CR diffusion. Injecting cosmic rays into star-forming regions can provide significant pressure support for the interstellar medium, suppressing star formation and thickening the disk. We find that CR diffusion plays a central role in driving superwinds, rapidly transferring long-lived CRs from the highest density regions of the disk to the ISM at large, where their pressure gradient can smoothly accelerate the gas out of the disk.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/27b1392a27689e9383659eee554d3ca7476bdda9

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Citations in the corpus

How Stellar Feedback Simultaneously Regulates Star Formation and Drives Outflows (2015, background): “…such as supernovae from runaway OB stars (e.g.Li et al. 2015) or cosmic rays (Uhlig et al. 2012; Booth et al. 2013; Hanasz et al. 2013; Salem & Bryan 2014; Salem et al. 2014; Girichidis et al. 2016), may provide the remaining momentum deposition necessary to accelerate the patch to…”
ON THE INTERPLAY BETWEEN STAR FORMATION AND FEEDBACK IN GALAXY FORMATION SIMULATIONS (2014, background): “Indeed, Booth et al. (2013) (see also Hanasz et al. 2013; Salem & Bryan 2014) demonstrated that if a modest fraction of the available supernova energy (∼ 10% of 1051 erg) is injected as a CR energy density, galactic winds can be driven effectively and can exhibit qualitatively different properties…”
Neutral hydrogen in galaxy haloes at the peak of the cosmic star formation history (2014, background): “…point to missing physics in our current calculations, such as magnetic fields and cosmic rays, which could play a significant role in injecting cool gas into halos (e.g., Booth et al. 2013; Salem & Bryan 2014) and in maintaining the integrity of cool gas in galactic winds (McCourt et al. 2014).”
Theoretical Challenges in Galaxy Formation (2016, background): “This is treated approximately either by streaming (Uhlig et al. 2012) or by isotropic diffusion with a typical diffusion coefficient (Booth et al. 2013, Enßlin et al. 2007, Jubelgas et al. 2008, Salem & Bryan 2014).”