Chan, T K and Kereš, Dušan and Gurvich, Alexander B and Hopkins, Philip F and Trapp, Cameron and Ji, Suoqing and Faucher-Giguère, Claude-André (2022) 'The impact of cosmic rays on dynamical balance and disc–halo interaction in L⋆ disc galaxies.', Monthly Notices of the Royal Astronomical Society, 517 (1). pp. 597-615.
Cosmic rays (CRs) are an important component in the interstellar medium, but their effect on the dynamics of the disc–halo interface (<10 kpc from the disc) is still unclear. We study the influence of CRs on the gas above the disc with high-resolution FIRE-2 cosmological simulations of late-type L galaxies at redshift z ∼ 0. We compare runs with and without CR feedback (with constant anisotropic diffusion κ ∼ 3 × 1029 cm2 s−1 and streaming). Our simulations capture the relevant disc–halo interactions, including outflows, inflows, and galactic fountains. Extra-planar gas in all of the runs satisfies dynamical balance, where total pressure balances the weight of the overlying gas. While the kinetic pressure from non-uniform motion (1 kpc scale) dominates in the mid-plane, thermal and bulk pressures (or CR pressure if included) take over at large heights. We find that with CR feedback, (1) the warm (∼104 K) gas is slowly accelerated by CRs; (2) the hot (>5 × 105 K) gas scale height is suppressed; (3) the warm-hot (2 × 104–5 × 105 K) medium becomes the most volume-filling phase in the disc–halo interface. We develop a novel conceptual model of the near-disc gas dynamics in low-redshift L galaxies: with CRs, the disc–halo interface is filled with CR-driven warm winds and hot superbubbles that are propagating into the circumgalactic medium with a small fraction falling back to the disc. Without CRs, most outflows from hot superbubbles are trapped by the existing hot halo and gravity, so typically they form galactic fountains.
|Full text:||(VoR) Version of Record|
Available under License - Creative Commons Attribution 4.0.
Download PDF (3037Kb)
|Publisher Web site:||https://doi.org/10.1093/mnras/stac2236|
|Publisher statement:||This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.|
|Date accepted:||02 August 2022|
|Date deposited:||21 November 2022|
|Date of first online publication:||19 August 2022|
|Date first made open access:||21 November 2022|
Save or Share this output
|Look up in GoogleScholar|