The Fermi-LAT high-latitude Survey: Source Count Distributions and the Origin of the Extragalactic Diffuse Background

Understand

This is the first of a series of papers aimed at characterizing the populations detected in the high-latitude sky of the {\it Fermi}-LAT survey.

• In this work we focus on the intrinsic spectral and flux properties of the source sample.
• We show that when selection effects are properly taken into account, {\it Fermi} sources are on average steeper than previously found (e.g.
• in the bright source list) with an average photon index of 2.40$\pm0.02$ over the entire 0.1--100\,GeV energy band.