1305.5249 (Yan Gong et al.)

The extragalactic background light from the measurements of the attenuation of high-energy gamma-ray spectrum    [PDF]

Yan Gong, Asantha Cooray

The attenuation of high-energy gamma-ray spectrum due to the electron-positron pair production against the extragalactic background light (EBL) provides an indirect method to measure the EBL of the universe. We use the measurements of the absorption features of the gamma-rays from blazars as seen by Fermi Gamma-ray Space Telescope to explore the EBL flux density and constrain the EBL spectrum, star formation rate density (SFRD) and photon escape fraction from galaxies out to z=6. Our results are basically consistent with the existing determinations of the quantities. We find a larger escape fraction at high redshifts, especially at z=3, compared to the result from the recent Lyman-alpha measurements. The average SFRD we obtain at z>3 is higher than the results from the UV data but agrees well with that from the gamma-ray burst observations. Our SFRD at z>~6 is sufficiently high enough to reionize the universe.

View original: http://arxiv.org/abs/1305.5249