First sources in infrared light: stars, supernovae and miniquasars

The cosmic infrared background (IRB) at wavelengths between 1 and 3 μm provides a useful probe of early star formation prior to and during reionization. To explain the high optical depth to electron scattering, as measured by the Wilkinson Microwave Anisotropy Probe (WMAP), one requires significant star formation activity at redshifts of 10 and higher. In addition to massive stars, the IRB flux may be contributed by a population of early miniquasars. We study the relative contributions from first stars, supernovae and quasars to the IRB for reasonable star formation rates at high redshift. If miniquasars radiate efficiently at the Eddington limit, current background measurements limit the fraction of mass in first stars that is converted to seed black holes to be roughly less than 10 per cent. In the case of supernovae, though an individual supernova is much brighter than the progenitor star, due to the shorter lifetime (of the order of a few months), the fractional contribution to the IRB remains at a level of 10 per cent and below when compared to the same contribution from stars. The bright supernovae may, however, be directly detectable by future large ground-based and space telescopes.