Clustering of gamma-ray selected 2LAC Fermi Blazars

TL;DR

This study measures the clustering of gamma-ray selected Blazars, revealing they reside in massive dark matter halos and share similar environments regardless of their spectral differences, impacting dark matter detection efforts.

Contribution

First measurement of the clustering of gamma-ray selected Blazars, linking their environment and halo mass, and supporting unified models of radio-loud AGN and Blazars.

Findings

Bl Lacs and FSRQs reside in massive dark matter halos (~10^13.4 Msun/h)

Blazars are found in dense galaxy group environments

Blazars may significantly contaminate dark matter annihilation signals

Abstract

We present the first measurement of the projected correlation function of 485 gamma-ray selected Blazars, divided in 175 BLLacertae (BL Lacs) and 310 Flat Spectrum Radio Quasars (FSRQs) detected in the 2-year all-sky survey by Fermi-Large Area Telescope. We find that Fermi BL Lacs and FSRQs reside in massive dark matter halos (DMHs) with logMh=13.35+0.20/-0.14 and logMh = 13.40+0.15/-0.19 Msun/h, respectively, at low (z=0.4) and high (z =1.2) redshift. In terms of clustering properties, these results suggest that BL Lacs and FSRQs are similar objects residing in the same dense environment typical of galaxy groups, despite their different spectral energy distribution, power and accretion rate. We find no difference in the typical bias and hosting halo mass between Fermi Blazars and radio-loud AGN, supporting the unifcation scheme simply equating radio-loud objects with misaligned Blazar counterparts. This similarity in terms of typical environment they preferentially live in, suggests that Blazars preferentially occupy the centre of DMHs, as already pointed out for radio-loud AGN. This implies, in light of several projects looking for the gamma-ray emission from DM annihilation in galaxy clusters, a strong contamination from Blazars to the expected signal from DM annihilation.