Variability: who cares? or…. Photometric redshift for XMM-COSMOS sources M.Salvato, G. Hasinger, O. Ilbert, G. Zamorani, M.Brusa + COSMOS collaboration Salvato et al. 2009,ApJ, accepted

In order to better understand the role (if any) of the AGN phase in Galaxy evolution, a complete CENSUS of AGN is crucial. get them all : Due to the interplay between host and Active Nucleous, No criterion can exist that can identify all AGN using a single waveband (i.e. see talks at this conference). get the right redshift: most of the sources are faint and we must rely on photometric redshifts.

even for Xray selected AGN usually, for z<1, the accuracy is not better than 0.06 (after removing 20% of outliers...) …or, in other words, something linke this…

Our results: I + AB <22.5 I + AB >22.5

Our results: I + AB <22.5 I + AB >22.5

Our results: I + AB <22.5 I + AB >22.5.

HOW? Correction for variability New templates Tons of photometric points WHAT IS MORE IMPORTANT ?

SDSS SUBARU BB IB 1 IB 2 About 2/5 of the XMM sample has clearly detected long term variability

Sources vary in a unpredictable way ? Additional ~1000 non X-ray detected galaxies are varying and there are currently under investigation currently under investigation

Templates } QSO2+S0 } TQSO1+I22491 Sy1.8 Sy2 MRK231 QSO S0 I22491 M82 Sp Sb

Relevance of templates and variability correction Both factors are crucial to reducing the number of outliers.

Among other results: Correct stellar/galaxy separation Correct relation between hardness ratio and SED and variability Correct relation between Xray luminosity and SED

QSO selection at high z via Lyman break Siana et al. 2008

Normal gals type II type I

Thank you! Ilbert et al Salvato et al..

SUMMARY Variability effects your work more than you think…