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.Comment: Accepted for publication in The Astrophysical Journa
