Clustering properties and environment of AGN R. Gilli, T. Miyaji, J. Silverman, G. Zamorani and many others (mainly from the COSMOS collaboration)

A few issues and questions Where do AGN live? (host galaxies, enviroment, dark matter halos) Does environment play a role in triggering an AGN? Mergers, galaxy interactions or internal secular processes? From AGN clustering: Duty cycle and lifetime Descendants and progenitors L/LEDD distribution Towards an evolutionary sequence

Clustering = spatial distribution The correlation function – w(θ), ξ(r), wp(rp) - is a statistical description of a spatial distribution: it simply measures how many pairs of objects are found over a random distribution

Random distribution

Highly clustered distribution

Clustering of dark matter and halos z=3.0 z=0.0 ξ(r) r [Mpc] z=0.0 z=3.0 Millennium simulation (Springel+05) Moustakas & Somerville 04 Halos form in high density peaks; at each redshift more massive halos are more clustered

Infos from AGN clustering Correlation length r0 ≈ powerlaw normalization On small scales (< 1-2 Mpc): objects in the same dark matter halo (1-halo term). Infos on the mechanisms triggering nuclear activity: mergers, fly by or secular processes? On large scales (>1-2 Mpc): objects in different halos (2-halo term). Infos on location of AGN within the cosmic web; hosting dark matter halos and galaxies; typical environment From 2dF

Host galaxies and dark matter halos at z~1 r0 (z~1) = 5.2+-1.5 Mpc/h Minimum halo mass: logM > 12.4 Msun/h AGN at z~1 seem to be preferentially hosted by massive galaxies (M*>2-3 1010 Msun) Consistent with non-clustering studies (eg. Silverman +09)

AGN lifetime from clustering tA nA tH nH = Optical QSOs (logLbol~46.5 , z~1-2): tA ~ 10-100 Myr X-ray AGN (logLbol~45.5 , z~1): tA ~ 1 Gyr

Clustering as a function of redshift Despite earlier claims, X-ray AGN cluster similarly to optically selected QSOs at the same redshifts Radio-galaxies, instead are more clustered. Halo mass, logM/Mo~12-12.5, typical of poor groups, seems the be the same at any epoch: is there any halo threshold mass for nuclear triggering?? CDFS Millennium halos

The Hickox et al. (2009) cartoon Threshold halo mass (group mass) to start the sequence through galaxy mergers

Descendants of z~0.7 X-ray AGN Red, early green, transitional blue, late Loh+10, GALEX X-ray AGN conserving scenario (Nusser & Davis 94, Moscardini +98): objects in halos with a given mass simply evolve without merging along the density field X-ray AGN at z~0.7 will switch off by z=0 and their relic SMBHs will be hosted by local bright (L~L*) early type galaxies

So mergers are the triggering mechanism? Hopkins+08 z<0.4 1-halo term QSOs are consistent with being triggered by mergers, Seyferts probably not Issue still to be solved..