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The impact of cosmic rays on dynamical balance and disc–halo interaction in L⋆ disc galaxies

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. ISSN 0035-8711. doi:10.1093/mnras/stac2236.

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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.

Item Type:Article
Related URLs:
URLURL TypeDescription
Chan, T. K.0000-0003-2544-054X
Kereš, Dušan0000-0002-1666-7067
Gurvich, Alexander B.0000-0002-6145-3674
Hopkins, Philip F.0000-0003-3729-1684
Trapp, Cameron0000-0001-7813-0268
Ji, Suoqing0000-0001-9658-0588
Faucher-Giguère, Claude-André0000-0002-4900-6628
Additional Information:We gratefully thank the referee, Mordecai-Mark Mac Low, for the careful reading and suggestions. We thank Bili Dong for the help with YT. We thank Eliot Quataert, Norman Murray, and Matthew Orr for helpful discussions. We are grateful for stimulating ideas and discussions during the KITP program – Fundamentals of Gaseous Halos (grant number NSF PHY-1748958). TKC was supported by the Science and Technology Facilities Council (STFC) through Consolidated Grants ST/P000541/1 and ST/T000244/1 for Astronomy at Durham. DK was supported by NSF through grants AST-1715101 and AST-2108314 and Cottrell Scholar Award from the Research Corporation for Science Advancement. ABG was supported by a National Science Foundation Graduate Research Fellowship Program under grant DGE-1842165 and was additionally supported by the NSF under grants DGE-0948017 and DGE-145000, and from Blue Waters as a graduate fellow which is itself supported by the NSF (awards OCI-0725070 and ACI-1238993). Support for PFH and co-authors was provided by an Alfred P. Sloan Research Fellowship, NSF Collaborative Research Grant #1715847 and CAREER grant #1455342, and NASA grants NNX15AT06G, JPL 1589742, 17-ATP17-0214. SJ is supported by a Sherman Fairchild Fellowship from Caltech, the Natural Science Foundation of China (grants 12133008, 12192220, and 12192223), and the science research grants from the China Manned Space Project (No. CMS-CSST-2021-B02). CAFG was supported by NSF through grants AST-1715216, AST-2108230, and CAREER award AST-1652522; by NASA through grant 17-ATP17-0067; by STScI through grant HST-AR-16124.001-A; and by the Research Corporation for Science Advancement through a Cottrell Scholar Award. The simulation presented here used computational resources granted by the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation grant no. OCI-1053575, specifically allocation TG-AST120025. The simulations are additionally supported by allocations AST21010 and AST20016 from the NSF and TACC. Our analysis is run on the Triton Shared Computing Cluster in the San Diego Supercomputer Center (San Diego Supercomputer Center 2022). This work also used YT (Turk et al. 2011), MATPLOTLIB (Hunter 2007), NUMPY (van der Walt, Colbert & Varoquaux 2011), SCIPY (Jones et al. 2001), and NASA’s Astrophysics Data System. The data used in this work here were, in part, hosted on facilities supported by the Scientific Computing Core at the Flatiron Institute, a division of the Simons Foundation.
Group:Astronomy Department, TAPIR, Walter Burke Institute for Theoretical Physics
Funding AgencyGrant Number
NSF Graduate Research FellowshipDGE-1842165
NSF Graduate Research FellowshipDGE-0948017
NSF Graduate Research FellowshipDGE-1450006
Science and Technology Facilities Council (STFC)ST/P000541/1
Science and Technology Facilities Council (STFC)ST/T000244/1
Cottrell Scholar of Research CorporationUNSPECIFIED
Natural Science Foundation of China12133008
Natural Science Foundation of China12192220
Natural Science Foundation of China12192223
China Manned Space ProjectCMS-CSST-2021-B02
Alfred P. Sloan FoundationUNSPECIFIED
Simons FoundationUNSPECIFIED
Sherman Fairchild FoundationUNSPECIFIED
Issue or Number:1
Record Number:CaltechAUTHORS:20221024-125854800.20
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:117551
Deposited By: Research Services Depository
Deposited On:29 Oct 2022 22:06
Last Modified:01 Nov 2022 17:54

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