Cosmic evolution of AGN in several X-ray bands Jacobo Ebrero Instituto de Física de Cantabria (CSIC-UC) X-ray Universe Symposium 2008 Granada, 27th May 2008

Outline Introduction X-ray samples The NH function of Ultrahard sources The X-ray luminosity function Results Summary X-ray Universe Symposium 2008 Granada, 27th May 2008

Introduction We have computed the luminosity function of a combination of nearly completely identified AGN surveys in 3 different energy bands (0.5-2 keV, 2-10 keV and 4.5-7.5 keV) up to z = 3. The backbone of this study is the XMS survey, a flux-limited highly complete survey at medium fluxes. It is 96% complete in the 0.5-2 keV band, and over 86% in the others. We have combined XMS with other highly complete shallower and deeper surveys in order to obtain a wider LX-z plane coverage. Detailed spectral information is available for most of the sources detected in the 4.5-7.5 keV band thus allowing us to study their absorption properties.

Samples Soft (0.5 – 2 keV): Survey NAGN Flux limit (cgs) XMS 178 1.5 x 10-14 CDF-S 226 5.5 x 10-17 RIXOS 222 3.0 x 10-14 RDS 39 5.5 x 10-15 RBS 310 2.5 x 10-12 Overall sky coverage XMS CDF-S RDS RIXOS RBS

Samples Hard (2 – 10 keV): Survey NAGN Flux limit (cgs) Overall sky coverage XMS CDF-S AMSS Hard (2 – 10 keV): Survey NAGN Flux limit (cgs) XMS 120 3.3 x 10-14 CDF-S 236 4.5 x 10-16 AMSS 79 3.0 x 10-13

Samples Ultrahard (4.5 – 7.5 keV): XMS 57 6.8 x 10-15 Overall sky coverage XMS HBS Ultrahard (4.5 – 7.5 keV): Survey NAGN Flux limit (cgs) XMS 57 6.8 x 10-15 HBS 62 7.0 X 10-14

The NH function of Ultrahard sources We have used the joint XMS/HBS sample in the 4.5-7.5 keV band (119 identified AGN). The NH function is a probability distribution for the absorption column density as a function of LX and redshift. 43 < log L4.5-7.5 < 43.75 Ebrero et al., 2008, in preparation

The X-ray luminosity function We first calculate the binned XLF using the 1/Va method: We perform a ML fit to an analytic model using all the available information in each source without binning. We use a Luminosity-dependent Density Evolution (LDDE) model: For the Ultrahard sources we use absorption-corrected data and we introduce the best-fit NH function when performing the fit.

XLF: Results Soft (0.5-2 keV)

Evolution in LX and redshift present. XLF: Results Soft (0.5-2 keV) Evolution in LX and redshift present.

XLF: Results Hard (2-10 keV)

Evolution in LX and redshift present. XLF: Results Hard (2-10 keV) Evolution in LX and redshift present.

XLF: Results Ultrahard (4.5-7.5 keV)

Evolution in LX and redshift present. XLF: Results Ultrahard (4.5-7.5 keV) Evolution in LX and redshift present.

XLF: Results ? Comoving density Hard Soft Ultrahard High-luminosity AGNs reach a maximum in density earlier than the less luminous AGN. Growth and formation more efficient for high-luminosity AGN. ?

Accretion rate density XLF: Results Accretion rate density Soft Hard Ultrahard The majority of the accretion rate density in the Universe is produced by low-luminosity AGN. High-luminosity AGN reach a maximum in the accretion rate density earlier than the less luminous AGN.

Summary We have used the XMS survey along with other highly complete shallower and deeper surveys to study the cosmic evolution of AGN in three energy bands: Soft (0.5-2 keV), Hard (2-10 keV) and Ultrahard (4.5-7.5 keV). The XLF has been computed by ML fitting to an analytic model (LDDE). We have modelled the intrinsic absorption of the Ultrahard sample (NH function). We found that the fraction of absorbed AGN depends on the X-ray luminosity but not on redshift. High-luminosity AGN grow and feed more efficiently in the early stages of the Universe than the less luminous AGN, and are fully formed at redshifts ~1.5-2. The evolution of AGN along cosmic time is therefore not caused by changes in the absorption environment but by intrinsic variations in the accretion rate at different epochs of the Universe.