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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. (2018) Cosmic ray feedback in the FIRE simulations: constraining cosmic ray propagation with GeV gamma ray emission. . (Unpublished) http://resolver.caltech.edu/CaltechAUTHORS:20190206-105655182

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Abstract

We present the first results of cosmic ray (CR) feedback implemented 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 newly-developed 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 with constant isotropic diffusion coefficients κ ∼ 3 × 10^(28−29) cm^2 s^(−1). Advection-only and streaming-only models (even allowing for super-Alfvenic streaming speeds) 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 disk 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 halos with scale heights of several kpc to several tens of kpc.


Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription
http://arxiv.org/abs/1812.10496arXivDiscussion Paper
ORCID:
AuthorORCID
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
Hayward, C. C.0000-0003-4073-3236
Additional Information:We thank Patrick Diamond, Ellen Zweibel, Michael Norman, and Todd Thompson for insightful suggestions and advice and Bili Dong for his help with YT. 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 also made use of YT (Turk et al. 2011), matplotlib (Hunter 2007), numpy (van der Walt et al. 2011), scipy (Jones et al. 2001), and NASA’s Astrophysics Data System.
Group:TAPIR
Funders:
Funding AgencyGrant Number
NSFAST-1715101
Cottrell Scholar of Research CorporationUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
NSFAST-1715847
NSFAST-1455342
NASANNX15AT06G
JPL1589742
JPL17-ATP17-0214
Simons FoundationUNSPECIFIED
NSFAST-1715070
NSFAST-1517491
NSFAST-1715216
NSFAST-1652522
NASANNX15AB22G
NASA17-ATP17-0067
NSFOCI-1053575
NSFTG-AST120025
NSFTG-AST130039
NSFOAC-1713353
NASASMD-16-7592
Subject Keywords:galaxies: evolution — galaxies: kinematics and dynamics
Record Number:CaltechAUTHORS:20190206-105655182
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20190206-105655182
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:92734
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:07 Feb 2019 15:47
Last Modified:07 Feb 2019 15:47

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