Cosmic-Ray Injection from Star-Forming Regions

Eric Carlson, Stefano Profumo, and Tim Linden
Phys. Rev. Lett. 117, 111101 – Published 9 September 2016
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Abstract

At present, all physical models of diffuse Galactic γ-ray emission assume that the distribution of cosmic-ray sources traces the observed populations of either OB stars, pulsars, or supernova remnants. However, since H2-rich regions host significant star formation and numerous supernova remnants, the morphology of observed H2 gas (as traced by CO line surveys) should also provide a physically motivated, high-resolution tracer for cosmic-ray injection. We assess the impact of utilizing H2 as a tracer for cosmic-ray injection on models of diffuse Galactic γ-ray emission. We employ state-of-the-art 3D particle diffusion and gas density models, along with a physical model for the star-formation rate based on global Schmidt laws. Allowing a fraction, fH2, of cosmic-ray sources to trace the observed H2 density, we find that a theoretically well-motivated value fH20.200.25 (i) provides a significantly better global fit to the diffuse Galactic γ-ray sky and (ii) highly suppresses the intensity of the residual γ-ray emission from the Galactic center region. Specifically, in models utilizing our best global fit values of fH20.200.25, the spectrum of the galactic center γ-ray excess is drastically affected, and the morphology of the excess becomes inconsistent with predictions for dark matter annihilation.

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  • Received 15 October 2015

DOI:https://doi.org/10.1103/PhysRevLett.117.111101

© 2016 American Physical Society

Physics Subject Headings (PhySH)

Gravitation, Cosmology & Astrophysics

Authors & Affiliations

Eric Carlson* and Stefano Profumo

  • Department of Physics and Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, California 95064, USA

Tim Linden

  • Kavli Institute for Cosmological Physics, University of Chicago, Illinois 60637, USA and Center for Cosmology and AstroParticle Physics (CCAPP) and Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA

  • *erccarls@ucsc.edu
  • linden.70@osu.edu
  • profumo@ucsc.edu

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Issue

Vol. 117, Iss. 11 — 9 September 2016

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