Clustering properties and environment of AGN

R. Gilli, T. Miyaji, J. Silverman, G. Zamorani

and many others (mainly from the COSMOS collaboration)

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

A few issues and questions

Clustering = spatial distribution

The correlation function – w(θ), ξ(r), wp(rp) - is a statisticaldescription of a spatial distribution: it simply measures howmany pairs of objects are found over a random distribution

Random distribution

Highly clustered distribution

Clustering of dark matter and halos

Millennium simulation (Springel+05)

z=3.0 z=0.0

ξ(r)

r [Mpc]

Moustakas & Somerville 04

z=3.0

z=0.0

Halos form in high density peaks; at each redshift more massive halos are more clustered

On small scales (< 1-2 Mpc): objects in the same dark matter halo (1-halo term).Infos on the mechanisms triggeringnuclear 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 thecosmic web;hosting dark matter halos and galaxies; typical environment

Infos from AGN clustering

From 2dF

Correlation length r0 ≈ powerlaw normalization

Host galaxies and dark matter halos at z~1

Minimum halo mass: logM > 12.4 Msun/h

AGN at z~1 seem tobe preferentially hosted by massivegalaxies (M*>2-3 1010 Msun)Consistent with non-clustering studies (eg. Silverman +09)

r0 (z~1) = 5.2+-1.5 Mpc/h

AGN lifetime from clustering

Optical QSOs (logLbol~46.5 , z~1-2): tA ~ 10-100 MyrX-ray AGN (logLbol~45.5 , z~1): tA ~ 1 Gyr

tA nA

tH nH

=

Clustering as a function of redshift

Despite earlier claims, X-ray AGN cluster similarly to opticallyselected QSOs at the same redshifts

Radio-galaxies, instead are moreclustered.

Halo mass, logM/Mo~12-12.5,typical of poor groups, seems the be the same at anyepoch: is there any halo thresholdmass for nuclear triggering??

Millennium halos

CDFS

The Hickox et al. (2009) cartoonThreshold halo mass (group mass) to start the sequence through galaxymergers

Descendants of z~0.7 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

Red, early

green, transitional

blue, late

Loh+10, GALEX

X-ray AGN

So mergers are the triggering mechanism?Hopkins+08

QSOs are consistent with being triggered by mergers, Seyferts probably notIssue still to be solved..

z<0.4

1-halo term