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 IB1IB2

About 2/5 of the XMM sample hasclearly detectedlong term variability

Sources vary in a unpredictable way

?

Additional ~1000 non X-ray detected

Additional ~1000 non X-ray detected

galaxies are varying and there are

galaxies are varying and there are

currently under investigation

currently under investigation

Templates

}QSO2+S0

}TQSO1+I22491

Sy1.8Sy2

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…

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.