Evolution of Absorption in AGN Günther Hasinger NGC 3079 Sy2 + SB Gal HST & Chandra Ringberg HE Meeting February,

The X-ray background Courtesy: M. Brusa, M. Ajello

G.H., Miyaji & Schmidt, 2005Ueda et al., 2003, based on ~1000 AGN-1based on ~250 AGN AGN Space Densities in soft and hard band Very similar behaviour in hard and soft band. Soft samples go deeper and are more complete. What is the role of selection effects? Brandt & G.H., 2005

Study of evolution through a Meta-analysis of all available high-quality surveys

Meta-Survey Analysis COSMOS

Summary of Surveys used + COSMOS (1058 AGN)

Type1/Type2 Discrimination absorbed unabsorbed

Meta-Sample Filled circles: AGN-1 Open circles: AGN-2

Number Counts unidentified photo-z

Correcting Incompleteness

Type-2 fraction vs. Luminosity Maiolino et al., Spitzer Simpson et al., SDSS This work: corrected uncorrected for z incompletn. Clear trend of less absorption for more luminous AGN in different samples  High-luminosity AGN can clean out their environment  Break-down of the strong unified AGN model G. Hasinger (2008)

Evolution of the fraction of obscured AGN? La Franca et al. 2005

Type2/Total AGN vs. Redshift Gilli et al. no evolution prediction This work: corrected uncorrected for z incompletn.

Comparison of systematic effects This work: X-ray/optical classification BLAGN classification Treister &Urry 2006/2008

In Luminosity, including COSMOS

Type-2 relation as a function of redshift

Evolution of type-2 normalization Formally barely consistent with Treister & Urry 2006 and with La Franca et al., But more significant and flattening Fit by (1+z) α with α=0.76±0.11 up to z=2 Effect highly significant This work La Franca et al. 2005

A bi-modal AGN evolution scenario

G.H., Miyaji & Schmidt, 2005Ueda et al., 2003, based on ~1000 AGN-1based on ~250 AGN Densities in soft and hard band Very similar behaviour in hard and soft band. Soft samples go deeper and are more complete. Brandt & G.H., 2005

History of Merger Events Press-Schechter treatment shows that Major AND minor mergers follow almost the same evolution with a peak at redshift ~ 3. The merger abundance can explain the evolution of luminous QSOs quite well. Quasars We need a completely separate, more abundant BH triggereing mode showing up much later in the history of the Universe. Why so late? c/f cosmic downsizing of galaxies. AGN Kochfar, Burkert, Hasinger, 2007, in prep.)

Where do the late AGN live? Silverman et al., 2007, submitted to A&A They live in sheets in the „green valley“ and have bulges/BHs plus disks Disks Bulges Blue Cloud Red Sequence Green Valley

The GALEX Perspective SDSS local Seyferts observed with GALEX show this trend even clearer: T. Heckman et al., 2007, priv. comm. S. Faber et al., 2005, astro-ph Seyferts

Conclusions The X-ray background is made by AGN X-rays detect (almost) all AGN The unified AGN model breaks down High-luminosity AGN clean out environment Significant obscuration evolution seen up to z~2 AGN evolution needs two modes: mergers at high z and a slow rejuvenation of disks later AGN populate the „green valley“ from above