Characterizing the local gamma-ray Universe via angular cross-correlations

TL;DR

This paper uses cross-correlation of Fermi-LAT gamma-ray data with galaxy catalogs to analyze the local gamma-ray universe, revealing dominant AGN contributions and potential dark matter signals.

Contribution

It introduces a method of using angular cross-correlations with galaxy catalogs to characterize the local gamma-ray sources and their origins.

Findings

AGN emissions dominate the gamma-ray signal

Star-forming galaxies contribute subdominantly

Hints of possible dark matter signals are discussed

Abstract

With a decade of gamma-ray data from the Fermi-LAT telescope, we can now hope to answer how well we know the local Universe at gamma-ray frequencies. On the other hand, with gamma-ray data alone it is not possible to directly access the distance of the emission and to point out the origin of unresolved sources. This obstacle can be overcome by cross-correlating the gamma-ray data with catalogs of objects with well-determined redshifts and positions. In this work, we cross-correlate Fermi-LAT skymaps with the 2MPZ catalog to study the local $z<0.2$ gamma-ray Universe, where about ten percent of the total unresolved gamma-ray background is produced. We find the signal to be dominated by AGN emissions, while star forming galaxies provide a subdominant contribution. Possible hints for a particle DM signal are discussed.