Download - Clustering properties and environment of AGN
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