Constraining the cosmic abundance of stellar remnants with multi-TeV gamma-rays
David S. Graff, Katherine Freese, Terry Walker, Marc Pinsonneault
Abstract
If galactic halos contain stellar remnants, the infra-red flux from the remnant progenitors would contribute to the opacity of multi-TeV gamma-rays. The multi-TeV gamma-ray horizon is established to be at a redshift z>0.034 by the observation of the blazar Mkn501 . By requiring that the optical depth due to γγ---> e+ e- be less than one for a source at z=0.034 we limit the cosmological density of stellar remnants, Omegarm (2-4) x 10-3 h70-1 (h70 is the Hubble constant in units of 70 km sec-1 Mpc-1) and thus strongly constrain stellar remnants as a cosmologically significant source of dark matter.
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