Constraining the Cosmic Abundance of Stellar Remnants with Multi-T[CLC]e[/CLC]V Gamma Rays

Abstract
If stellar remnants are cosmologically significant, the infrared flux from the remnant progenitors would contribute to the opacity of multi-TeV γ-rays. The multi-TeV γ-ray horizon is established to be at a redshift z > 0.034 by the observation of the blazar Mrk 501. By requiring that the optical depth due to γγ → e+e- be less than 1 for a source at z = 0.034, we limit the cosmological density of stellar remnants, Ωrm ≤ (2-4) × 10-3 h (h70 is the Hubble constant in units of 70 km s-1 Mpc-1), and thus strongly constrain stellar remnants as a cosmologically significant source of dark matter.
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