Cosmic infrared background from Population III stars and its effect on spectra of high-z gamma-ray bursts

Abstract

We discuss the contribution of Population III stars to the near-IR (NIR) cosmic infrared background (CIB) and its effect on spectra of high-$z$ high-energy gamma-ray bursts (GRBs). It is shown that if Population III were massive stars, the claimed NIR CIB excess will be reproduced if only ~ 4+/-2% of all baryons went through these stars. Regardless of the precise value of the NIR CIB produced by them, they would leave enough photons to provide a large optical depth for high-energy photons from high-z GRBs. Observations of such GRBs are expected following the planned launch of NASA's GLAST mission. The presence or absence of such damping in the spectra of high-$z$ GRBs will then provide important information on the emissions from the Population III. The location of this cutoff may also serve as an indicator of the GRB's redshift.

Ap.J.Letters, in press. Revision includes discussion of CIB and low-z blazars. Some typos corrected and minor error in Fig.2 corrected