Constraining the cosmic abundance of stellar remnants with multi-TeV gammarays

If stellar remnants are cosmologically significant, the infrared 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 Mrk 501. By requiring that the opt ical depth due to gamma gamma --> e(+)e(-) be less than 1 for a source at z = 0.034, we limit the cosmological density of stellar remnants, Omega(rm) less than or equal to (2-4) x 10(-3) h(70)(-1) (h(70) is the Hubble constan t in units of 70 km s(-1) Mpc(-1)), and thus strongly constrain stellar rem nants as a cosmologically significant source of dark matter.