Spherical cows in dark matter indirect detection
Name
1606.00433.pdf
Description
Accepted version
Size
2.41 MB
Format
Adobe PDF
Checksum (MD5)
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Author(s)
Bernal, Nicolás
Necib, Lina
Slatyer, Tracy Robyn
Date Issued
December 2016
Journal
Journal of Cosmology and Astroparticle Physics
Publisher
IOP Publishing
Citation
Bernal, Nicolas et al. "Spherical cows in dark matter indirect detection." Journal of Cosmology and Astroparticle Physics 2016, 17 (December 2016): 30 © 2016 IOP Publishing Ltd and Sissa Medialab srl.
Version
Author's final manuscript
Abstract
Dark matter (DM) halos have long been known to be triaxial, but in studies of possible annihilation and decay signals they are often treated as approximately spherical. In this work, we examine the asymmetry of potential indirect detection signals of DM annihilation and decay, exploiting the large statistics of the hydrodynamic simulation Illustris. We carefully investigate the effects of the baryons on the sphericity of annihilation and decay signals for both the case where the observer is at 8.5 kpc from the center of the halo (exemplified in the case of Milky Way-like halos), and for an observer situated well outside the halo. In the case of Galactic signals, we find that both annihilation and decay signals are expected to be quite symmetric, with axis ratios very different from 1 occurring rarely. In the case of extragalactic signals, while decay signals are still preferentially spherical, the axis ratio for annihilation signals has a much flatter distribution, with elongated profiles appearing frequently. Many of these elongated profiles are due to large subhalos and/or recent mergers. Comparing to gamma-ray emission from the Milky Way and X-ray maps of clusters, we find that the gamma-ray background appears less spherical/more elongated than the expected DM signal from the large majority of halos, and the Galactic gamma ray excess appears very spherical, while the X-ray data would be difficult to distinguish from a DM signal by elongation/sphericity measurements alone.
MIT Department
Massachusetts Institute of Technology. Center for Theoretical Physics
Massachusetts Institute of Technology. Department of Physics
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Creative Commons Attribution-Noncommercial-Share Alike
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DOI of Published Version
https://doi.org/10.1088/1475-7516/2016/12/030
