Measuring the extragalactic background light from very high energy gamma-ray observations of blazars

Abstract

The extragalactic background light (EBL) contains important information about stellar and galaxy evolution. It leaves imprint on the very high energy $\gamma$-ray spectra from sources at cosmological distances due to the process of pair production. In this work we propose to {\em measure} the EBL directly by extracting the collective attenuation effects in a number of $\gamma$-ray sources at different redshifts. Using a Markov Chain Monte Carlo fitting method, the EBL intensities and the intrinsic spectral parameters of $\gamma$-ray sources are derived simultaneously. No prior shape of EBL is assumed in the fit. With this method, we can for the first time to derive the spectral shape of the EBL model-independently. Our result shows the expected features predicted by the present EBL models and thus support the understanding of the EBL origin.