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Cosmic ray feedback in the FIRE simulations: constraining cosmic ray propagation with GeV gamma ray emission

Chan, T. K. and Kereš, D. and Hopkins, P. F. and Quataert, E. and Su, K.-Y. and Hayward, C. C. and Faucher-Giguère, C.-A. (2019) Cosmic ray feedback in the FIRE simulations: constraining cosmic ray propagation with GeV gamma ray emission. Monthly Notices of the Royal Astronomical Society, 488 (3). pp. 3716-3744. ISSN 0035-8711.

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We present the implementation and the first results of cosmic ray (CR) feedback in the Feedback In Realistic Environments (FIRE) simulations. We investigate CR feedback in non-cosmological simulations of dwarf, sub-L⋆ starburst, and L⋆ galaxies with different propagation models, including advection, isotropic, and anisotropic diffusion, and streaming along field lines with different transport coefficients. We simulate CR diffusion and streaming simultaneously in galaxies with high resolution, using a two-moment method. We forward-model and compare to observations of γ-ray emission from nearby and starburst galaxies. We reproduce the γ-ray observations of dwarf and L⋆ galaxies with constant isotropic diffusion coefficient κ∼3×10^(29)cm^2s^(-1)⁠. Advection-only and streaming-only models produce order of magnitude too large γ-ray luminosities in dwarf and L⋆ galaxies. We show that in models that match the γ-ray observations, most CRs escape low-gas-density galaxies (e.g. dwarfs) before significant collisional losses, while starburst galaxies are CR proton calorimeters. While adiabatic losses can be significant, they occur only after CRs escape galaxies, so they are only of secondary importance for γ-ray emissivities. Models where CRs are ‘trapped’ in the star-forming disc have lower star formation efficiency, but these models are ruled out by γ-ray observations. For models with constant κ that match the γ-ray observations, CRs form extended haloes with scale heights of several kpc to several tens of kpc.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Chan, T. K.0000-0003-2544-054X
Kereš, D.0000-0002-1666-7067
Hopkins, P. F.0000-0003-3729-1684
Quataert, E.0000-0001-9185-5044
Su, K.-Y.0000-0003-1598-0083
Hayward, C. C.0000-0003-4073-3236
Faucher-Giguère, C.-A.0000-0002-4900-6628
Additional Information:© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2019 July 8. Received 2019 July 2; in original form 2018 December 24. Published: 10 July 2019. We thank the anonymous referee for the detailed comments that helped to improve this manuscript. We thank Patrick Diamond, Ellen Zweibel, Michael Norman, and Todd Thompson for insightful suggestions and advice, Eve Ostriker for pointing out a typo, and Bili Dong for his help with YT. We would like to thank the Simons Foundation and the participants of the Galactic Superwinds symposia for stimulating discussions. TKC and DK were supported by NSF grant AST-1715101 and the Cottrell Scholar Award from the Research Corporation for Science Advancement. Support for PFH 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. EQ was supported in part by a Simons Investigator Award from the Simons Foundation and by NSF grant AST-1715070. The Flatiron Institute is supported by the Simons Foundation. CAFG was supported by NSF through grants AST-1517491, AST-1715216, and CAREER award AST-1652522, by NASA through grants NNX15AB22G and 17-ATP17-0067, and by a Cottrell Scholar Award from the Research Corporation for Science Advancement. 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. Numerical calculations were also run on the Caltech compute cluster ‘Wheeler’, allocations from XSEDE TG-AST130039 and PRAC NSF.1713353 supported by the NSF, and NASA HEC SMD-16-7592. This work uses data hosted by the Flatiron Institute’s FIRE data hub. This work also made use of 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.
Group:TAPIR, Astronomy Department
Funding AgencyGrant Number
Cottrell Scholar of Research CorporationUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
Simons FoundationUNSPECIFIED
Subject Keywords:galaxies: evolution – cosmic rays – gamma-rays: galaxies – galaxies: kinematics and dynamics – galaxies: starburst
Issue or Number:3
Record Number:CaltechAUTHORS:20190206-105655182
Persistent URL:
Official Citation:T K Chan, D Kereš, P F Hopkins, E Quataert, K-Y Su, C C Hayward, C-A Faucher-Giguère, Cosmic ray feedback in the FIRE simulations: constraining cosmic ray propagation with GeV γ-ray emission, Monthly Notices of the Royal Astronomical Society, Volume 488, Issue 3, September 2019, Pages 3716–3744,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:92734
Deposited By: George Porter
Deposited On:07 Feb 2019 15:47
Last Modified:07 Apr 2020 18:46

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