Dark matter searches in the gamma-ray extragalactic background via cross-correlations with galaxy catalogues

TL;DR

This study analyzes gamma-ray and galaxy catalog cross-correlations to search for dark matter signals, finding current data allows for a potential WIMP dark matter presence but does not strongly favor it, and sets limits on WIMP properties.

Contribution

It introduces a detailed modeling of gamma-ray and galaxy cross-correlations considering astrophysical sources and dark matter, providing new constraints on WIMP dark matter properties.

Findings

Current data allows for a WIMP dark matter signal but does not strongly favor it.

The method excludes thermal WIMP annihilation cross sections for masses up to a few tens of GeV.

Future data will improve constraints on dark matter and astrophysical source properties.

Abstract

We compare the measured angular cross-correlation between the Fermi-LAT gamma-ray sky and catalogues of extra-galactic objects with the expected signal induced by weakly interacting massive particle (WIMP) dark matter (DM). We include a detailed description of the contribution of astrophysical gamma-ray emitters such as blazars, misaligned AGN and star forming galaxies, and perform a global fit to the measured cross-correlation. Five catalogues are considered: SDSS-DR6 quasars, 2MASS galaxies, NVSS radio galaxies, SDSS-DR8 Luminous Red Galaxies and SDSS-DR8 main galaxy sample. To model the cross-correlation signal we use the halo occupation distribution formalism to estimate the number of galaxies of a given catalogue in DM halos and their spatial correlation properties. We discuss uncertainties in the predicted cross-correlation signal arising from the DM clustering and WIMP microscopic properties, which set the DM gamma-ray emission. The use of different catalogues probing objects at different redshifts reduces significantly, though not completely, the degeneracy among the different gamma-ray components. We find that the presence of a significant WIMP DM signal is allowed by the data but not significantly preferred by the fit, although this is mainly due to a degeneracy with the misaligned AGN component. With modest substructure boost, the sensitivity of this method excludes thermal annihilation cross sections at 95% C.L. for WIMP masses up to few tens of GeV. Constraining the low-redshift properties of astrophysical populations with future data will further improve the sensitivity to DM.