Journal Article

Enhancements to velocity-dependent dark matter interactions from tidal streams and shells in the Andromeda galaxy

Robyn E. Sanderson, Roya Mohayaee and Joe Silk

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 420, issue 3, pages 2445-2456
Published in print March 2012 | ISSN: 0035-8711
Published online February 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.20215.x
Enhancements to velocity-dependent dark matter interactions from tidal streams and shells in the Andromeda galaxy

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Dark matter substructures around nearby galaxies provide an interesting opportunity for confusion-free indirect detection of dark matter. We calculate the boost over a smooth background distribution of dark matter for gamma-ray emission from dark matter self-annihilations in tidal structures in M31, assuming a cross-section inversely proportional to the relative velocities of the dark matter particles as proposed by the Sommerfeld effect. The low velocity of the material in the structure results in a significant increase in gamma-ray emission compared to both the background halo and the predicted emission for a velocity-independent cross-section. We also calculate the expected signal for Fermi, for reasonable choices of the dark matter parameters. We find that for a cross-section proportional to v−2, the enhancement to the annihilation rate is sufficient to test the velocity dependence of the cross-section by spatial correlation with the stellar component of the M31 Giant Stream, given sufficient detector sensitivity.

Keywords: astroparticle physics; galaxies: individual: M31; galaxies: kinematics and dynamics; dark matter; gamma-rays: galaxies

Journal Article.  7979 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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