Cosmic evolution of AGN in several X-ray bands

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

2. 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

3. 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.

4. RBS RIXOS Overall sky coverage RDS CDF-S XMS Samples • Soft (0.5 – 2 keV): • SurveyNAGNFlux 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

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

6. HBS XMS Overall sky coverage Samples • Ultrahard (4.5 – 7.5 keV): • SurveyNAGNFlux limit (cgs) • XMS 57 6.8 x 10-15 • HBS 62 7.0 X 10-14

7. 43 < log L4.5-7.5 < 43.75 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. Ebrero et al., 2008, in preparation

8. We use a Luminosity-dependent Density Evolution (LDDE) model: 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. • For the Ultrahard sources we use absorption-corrected data and we introduce the best-fit NH function when performing the fit.

9. XLF: Results Soft (0.5-2 keV)

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

11. XLF: Results Hard (2-10 keV)

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

13. XLF: Results Ultrahard (4.5-7.5 keV)

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

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

16. Soft Hard Ultrahard XLF: Results Accretion rate density 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.

17. 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.