1. Space Density of Heavily-Obscured AGN, Star Formation and Mergers Ezequiel Treister (IfA, Hawaii Ezequiel Treister (IfA, Hawaii) Meg Urry, Priya Natarajan, Carie Cardamone, Kevin Schawinski (Yale), Eric Gawiser (Rutgers), Dave Sanders (IfA) Credit: ESO/NASA, the AVO project and Paolo Padovani

2. How to find high-z Obscured AGN? X-rays Tozzi et al. 2006 Trace rest-frame higher energies at higher redshifts  Less affected by obscuration Tozzi et al. claimed to have found 14 Compton- Thick AGN (reflection dominated) candidates in the CDFS. Polletta et al. (2006) report 5 CT QSOs (transmission dominated) in the SWIRE survey.

3. Fiore et al. 2008 Mid-IR X-ray Stacking F 24 /F R >1000 F 24 /F R <200 4  detection in X-ray stack. Hard spectral shape, harder than X- ray detected sources.  Good CT AGN candidates. Similar results found by Daddi et al. (2007) How to find high-z Obscured AGN?

4. Extended Chandra Deep Field-South Area: Area: 0.3 deg 2 X-rays: X-rays: Chandra 250ks/pointing Optical: Optical: Broad band UBVRIz (V=26.5)+ 18 Medium band filters (to R=26) Near-IR: Near-IR: JHK to K=20 (Vega) Mid-IR: Mid-IR: IRAC 3.6-8 microns + MIPS 24 microns to 35 µJy Spectroscopy: Spectroscopy: VLT/VIMOS, Magellan/IMACS (optical) VLT/SINFONI, Subaru/MOIRCS (near-IR)

5. Mid-IR Selection R-K (Vega) Log (f 24µm /f R ) - 211 sources with f 24  m /f R >1000 and R-K>4.5 - f 24  m >35  Jy - 18 X-ray detected Treister et al. ApJ in press

6. Redshift Distribution All Sources X-ray Detected X-ray Undetected - Photo-z for ~50% of the sources - X-ray sources brighter at all wavelengths - Spec-z for 3 X-ray sources and photo-z for 12 (83% complete). Treister et al. ApJ in press

7. Hardness Ratio  N H X-ray sources with redshift only - 2 unobscured - 11 obscured Compton-thin - 2 Compton Thick Assumed fixed  =1.9 Treister et al. ApJ in press

8. Stacking of non-Xrays Sources Soft (0.5-2 keV)Hard (2-8 keV) - ~4  detection in each band. - f soft =2.1x10 -17 erg cm -2 s -1. F hard = 8x10 -17 erg cm -2 s -1 - Sources can be detected individually in ~10 Msec. - Hardness ratio 0.13, N H =1.8x10 23 cm -2. - Alternatively, ~90% CT AGN and 10% star-forming galaxies. - Some evidence for a flux dependence. >95% CT AGN at the brightest bin, 80% at the lowest. Large error bars. Treister et al. ApJ in press

9. Rest-Frame Stacking Good fit with either NH  10 23 cm -2 or combination of CT AGN with star-forming galaxies. Consistent results with observed-frame stacking. Treister et al. ApJ in press

10. X-Ray to Mid-IR Ratio Both X-rays and 12µm good tracers of AGN activity. Observed ratios for X-ray sources consistent with local AGN (dashed line). Treister et al. ApJ in press

11. X-Ray to Mid-IR Ratio Effects of obscuration in X-ray band luminosity. Only important for Compton Thick sources. Treister et al. ApJ in press

12. X-Ray to Mid-IR Ratio ~100x lower ratio for X-ray undetected sources. Explained by N H ~5x10 24 to 10 25 cm -2 Treister et al. ApJ in press

13. X-Ray to Mid-IR Ratio Ratio for sources with L 12µm >10 43 erg/s (~80% of the sources) ~2-3x higher than star-forming galaxies Treister et al. ApJ in press

14. X-Ray to Mid-IR Ratio Using Lx/L 12µm =0.007 to separate AGN and star-forming galaxies  ~80% AGN, consistent with HR value. In sources with L 12µm >10 44 erg/s outside selection region fraction of AGN ~10%. Treister et al. ApJ in press

15. Morphologies Ground based: K,H,R HST/WFC3 J,H,Y GOODS-SUDF

16. Optical/Near-IR SED Fitting X-ray DetectedX-ray Undetected X-ray Detected X-ray Undetected - Median stellar mass for X-ray detected sources ~4.6x10 11 M sun. - For X-ray undetected source ~10 11 M sun. - Mild extinction values found in general. - Maximum Av~4 mags. - Median E(B-V)=0.6 for X-ray detected sources and 0.4 for undetected ones. Treister et al. ApJ in press Evidence for significant recent star formation in most sources

17. Heavily-Obscured AGN Space Density Systematic excess for L x >10 44 erg/s sources relative to extrapolation of Compton-thin LF Strong evolution in number of sources from z=1.5 to 2.5. Consistent with heavily- obscured phase after merger? Treister et al. ApJ in press

18. Obscured to Unobscured Quasar Ratio Treister et al. in prep.

19. The Merger-Quasar Connection Treister et al. in prep. Obscured quasars are the product of the gas-rich merger of two massive galaxies. After a time  t the quasar becomes unobscured.

20. The Merger-Quasar Connection Treister et al. in prep.  t=96  23 Myrs

21. Summary Mid-IR selection finds large number of heavily obscured AGN at z>1.5. Morphologies indicates interactions/mergers. Host galaxy masses ~10 11 M sun with young and obscured stellar populations. Strong evolution in numbers up to z~3. This could be evidence for a heavily obscured phase after quasar triggering. Mid-IR selection finds large number of heavily obscured AGN at z>1.5. Morphologies indicates interactions/mergers. Host galaxy masses ~10 11 M sun with young and obscured stellar populations. Strong evolution in numbers up to z~3. This could be evidence for a heavily obscured phase after quasar triggering.

22. IRAC Colors [5.8]-[8] (Vega) [3.6]-[4.5] (Vega) z=0-1 z>1 AGN Faint 8 µm Treister et al. ApJ submitted

23. Log N-Log S Treister et al. 2009

24. CT AGN Space Density z=0 LF Number of sources roughly consistent with extrapolation of Compton-thin LF Steeper evolution suggested by Della Ceca et al. (2008) and Yencho et al. (2009) work better Treister et al. ApJ submitted

25. IRAC Colors log (f 5.8 /f 3.6 ) log (f 8 /f 4.5 ) Faint 8µm Treister et al. ApJ submitted

26. Near to Mid-IR Colors - Distributions significantly different - X-ray detected sources much bluer - Average f 8 /f 24 =0.2 for X-ray sources and 0.04 for X-ray undetected sample BluerRedder Well explained by different viewing angle (30 o vs 90 o ) in the same torus model Can it be star-formation versus AGN? Treister et al. ApJ in press

27. Near to Mid-IR Colors Armus et al. 2007 ULIRG, LINER ULIRG, Sey2