Revisiting the clustering of narrow-line AGN in the local Universe:
  Joint dependence on stellar mass and color
  We investigate the clustering and dark halo properties for the narrow-line
active galactic nuclei (AGN) in the SDSS, particularly examining the joint
dependence on galaxy mass and color. AGN in galaxies with blue colors or
massive red galaxies with M*>~10^{10.5}Msun are found to show almost identical
clustering amplitudes at all scales to control galaxies of the same mass, color
and structural parameters. This suggests AGN activity in blue galaxies or
massive red galaxies is regulated by internal processes, with no correlation
with environment. The antibias of AGN at scales between ~100kpc and a few Mpc,
as found in Li et al. (2006) for the AGN as a whole, is observed only for the
AGN hosted by galaxies with red colors and relatively low masses
<10^{10.5}Msun. A simple halo model in which AGN are preferentially found at
dark halo centers can reproduce the observational results, but requiring a
mass-dependent central fraction which is a factor of ~4 higher than the
fraction estimated from the SDSS group catalogue. The same group catalogue
reveals that the host groups of AGN in red satellites tend to have lower halo
masses than control galaxies, while the host groups of AGN in red centrals tend
to form earlier, as indicated by a larger stellar mass gap between the two most
massive galaxies in the groups. Our result implies that the mass assembly
history of dark halos may play an additional role in the AGN activity in
low-mass red galaxies.
