Heavily-Obscured Super-Massive Black Holes at Low and High Redshift

1. Heavily-Obscured Super-Massive Black Holes at Low and High Redshift Ezequiel Treister (IfA, Hawaii) Meg Urry, Priya Natarajan, Carie Cardamone, Kevin Schawinski (Yale), Eric Gawiser (Rutgers), Dave Sanders (IfA) and the MUSYC collaboration Credit: ESO/NASA, the AVO project and Paolo Padovani

2. Active Galactic Nuclei (AGN) Urry & Padovani, 1995

3. Black hole–galaxy connection All (massive) galaxies have black holes Tight correlation of MBH with  Common BH/SFR Evolution AGN feedback important

4. All (Massive) Galaxieshave super-massive black holes

5. Black hole–galaxy connection All (massive) galaxies have black holes Tight correlation of MBH with  Common BH/SFR Evolution AGN feedback important

6. MBH-  Correlation Same relation for both active and non-active galaxies. Greene & Ho, 2006

7. Black hole–galaxy connection All (massive) galaxies have black holes Tight correlation of MBH with  Common BH/SFR Evolution AGN feedback important

8. Common BH/Star Formation Evolution Marconi et al. 2004

9. Black hole–galaxy connection All (massive) galaxies have black holes Tight correlation of MBH with  Common BH/SFR Evolution AGN feedback important

10. No AGN With AGN Feedback AGN Feedback Springel et al. 2005

11. Supermassive Black Holes Many obscured by gas and dust • How do we know that? • Local AGN Unification • Explain Extragalactic X-ray “Background” Credit: ESO/NASA, the AVO project and Paolo Padovani

12. Observed X-ray “Background” Frontera et al. (2006)

13. AGN in X-rays Photoelectric absorption affect mostly low energy emission making the observed spectrum look harder. Increasing NH

14. X-ray Background XRB well explained using a combination of obscured and unobscured AGN. • Setti & Woltjer 1989 • Madau et al. 1994 • Comastri et al. 1995 • Gilli et al. 1999,2001 • Treister & Urry 2005 • Gilli et al. 2007 • And others… Gilli et al., 2007

15. Compton Thick AGN • Defined as obscured sources with NH>1024 cm-2. • Very hard to find (even in X-rays). • Observed locally and needed to explain the X-ray background. • Number density highly uncertain. • May contribute significantly to SMBH accretion. • Multiwavelength observations are required to find them. • Hard X-rays (E>10keV) very useful locally.

16. Swift INTEGRAL

17. ISDC Swift Sources Tueller et al. 2007

18. Deep INTEGRAL Survey (3 Msec) Significance Image, 20-50 keV

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

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

21. Fraction of CT AGN X-ray background does not constrain density of CT AGN Treister et al. 2009

22. X-Ray Background Synthesis Treister et al. 2009

23. Contribution of CT AGN to the XRB Only 1% of the XRB comes from CT AGN at z≥2.  We can increase the # of CT AGN by ~10x and still fit the XRB. 50% 80% 90% Treister et al. 2009

24. CT AGN at High Redshift Treister et al. 2009

26. NuSTAR

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

28. How to find high-z CT AGN NOW? Mid-IR X-ray Stacking F24/FR>1000 F24/FR<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) Fiore et al. 2008

29. Extended Chandra Deep Field-South Area: 0.3 deg2 X-rays: Chandra 250ks/pointing Optical: Broad band UBVRIz (V=26.5)+ 18 Medium band filters (to R=26) Near-IR: JHK to K=20 (Vega) Mid-IR: IRAC 3.6-8 microns + MIPS 24 microns to 35 µJy Spectroscopy: VLT/VIMOS, Magellan/IMACS (optical) VLT/SINFONI, Subaru/MOIRCS (near-IR)

30. Mid-IR Selection • 211 sources with f24m/fR>1000 and R-K>4.5 • f24m>35Jy • 18 X-ray detected Log (f24µm/fR) R-K (Vega) Treister et al. ApJ in press

31. X-ray Undetected X-ray Detected All Sources Redshift Distribution • 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

32. Hardness Ratio  NH 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

33. Stacking of non-Xrays Sources Soft (0.5-2 keV) Hard (2-8 keV) • ~4 detection in each band. • fsoft=2.1x10-17erg cm-2s-1. Fhard= 8x10-17erg cm-2s-1 • Sources can be detected individually in ~10 Msec. • Hardness ratio 0.13, NH=1.8x1023cm-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

34. Rest-Frame Stacking Good fit with either NH1023cm-2 or combination of CT AGN with star-forming galaxies. Consistent results with observed-frame stacking. Treister et al. ApJ in press

35. 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

36. 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

37. X-Ray to Mid-IR Ratio ~100x lower ratio for X-ray undetected sources. Explained by NH~5x1024 to 1025cm-2 Treister et al. ApJ in press

38. X-Ray to Mid-IR Ratio Ratio for sources with L12µm>1043erg/s (~80% of the sources) ~2-3x higher than star-forming galaxies Treister et al. ApJ in press

39. X-Ray to Mid-IR Ratio Using Lx/L12µm=0.007 to separate AGN and star-forming galaxies  ~80% AGN, consistent with HR value. In sources with L12µm>1044erg/s outside selection region fraction of AGN ~10%. Treister et al. ApJ in press

40. Near to Mid-IR Colors • Distributions significantly different • X-ray detected sources much bluer • Average f8/f24=0.2 for X-ray sources and 0.04 for X-ray undetected sample Well explained by different viewing angle (30o vs 90o) in the same torus model Can it be star-formation versus AGN? Redder Bluer Treister et al. ApJ in press

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

42. Morphologies Ground based: K,H,R UDF GOODS-S HST/WFC3 J,H,Y

43. Optical/Near-IR SED Fitting X-ray Undetected X-ray Detected • Median stellar mass for X-ray detected sources ~4.6x1011 Msun. • For X-ray undetected source ~1011 Msun. Evidence for significant recent star formation in most sources X-ray Detected • 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. X-ray Undetected Treister et al. ApJ in press

44. Heavily-Obscured AGN Space Density Systematic excess for Lx>1044erg/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

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

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

47. The Merger-Quasar Connection t=7716 Myrs Treister et al. in prep.

48. Summary • Number of mildly CT sources at z~0 lower than expected. • Only ~1% of XRB comes from CT AGN at z~2. • Multiwalength surveys critical to find high-z CT AGN. • Mid-IR selection finds large number of CT AGN at z>1.5. • Morphologies indicates interactions/mergers. • Host galaxy masses ~1011 Msun 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.