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X-ray selected Type-2 QSOs: high luminosity in heavily obscured AGN

X-ray selected Type-2 QSOs: high luminosity in heavily obscured AGN. Vincenzo Mainieri ESO. -. G. Hasinger, M. Brusa, N. Cappelluti, K. Iwasawa, M. Salvato M. Bolzonella, A. Comastri, F. Fiore, R. Gilli, S. Lilly, J. Silverman, G. Zamorani + COSMOS. OUTLINE: COSMOS Survey

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X-ray selected Type-2 QSOs: high luminosity in heavily obscured AGN

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  1. X-ray selected Type-2 QSOs: high luminosity in heavily obscured AGN Vincenzo Mainieri ESO - G. Hasinger, M. Brusa, N. Cappelluti, K. Iwasawa, M. Salvato M. Bolzonella, A. Comastri, F. Fiore, R. Gilli, S. Lilly, J. Silverman, G. Zamorani + COSMOS The X-ray Universe 2008

  2. OUTLINE: • COSMOS Survey • Selection criteria • Comparison with SDSS QSO-2 • Comparison with MIR selection criteria • Multi-wavelength properties • Host galaxy properties • Morphology • Stellar masses • Star formation rates • Conclusions The X-ray Universe 2008

  3. Why studying QSO-2? • Quantifying the population of obscured quasars is essential for many applications: • relating the present mass density of BH to the accretion history of the entire AGN population (e.g. Soltan 1982; Yu & Tremaine 2002; Marconi et al. 2004) • understand the origin of the cosmic XRB (e.g. Comastri et al. 1995; Gilli et al. 2007) • studying the effects of luminosity on AGN structure (e.g. Lawrence 1991; Urry & Padovani 1995; Hopkins et al. 2006; Hasinger 2008) The X-ray Universe 2008

  4. QSO-2 selection criteria • Radio: radio-loud QSO-2 have been know for decades from radio surveys, narrow line radio galaxies (see McCarthy 1993 for a review). They probably represents ~10% of the whole population • Optical : candidates selected as objects with narrow (FWHM<1000 km s-1) permitted emission lines and high ionization line ratios characteristic of non-stellar ionizing radiation (e.g. Djorgovski et al. 2001, DPSS) • SDSS (Zakamska et al. 2003; Reyes et al. 2008): • 887 QSO-2 with z<0.83 • MB<-23 --> L[OIII] > 3 x 108 LSUN • X-ray: hard X-ray spectra and high X-ray luminosity • NH>1022 cm-2 • LX>1044 erg s-1 • (e.g. Norman et al. 2001, Dawson et al. 2001, Mainieri et al. 2002, Stern et al. 2002, Della Ceca et al. 2003, Perola et al. 2004, Szokoly et al. 2004, Barger et al. 2005, Mateos et al. 2005, Krumpe et al. 2008, ….) • Mid-IR: the emission absorbed by the circumnuclear material is thermally re-emitted in the IR (e.g. Lacy et al. 2005, Stern et al. 2005, Martinez-Sansigre et al. 2006, Polletta et al. 2007, Daddi et al. 2008, Fiore et al. 2008) The X-ray Universe 2008

  5. PI N. Scoville http://cosmos.astro.caltech.edu/ The X-ray Universe 2008

  6. COSMOS major components (in order of appearance) : HST/ACS (I-band – 590 orbits – I(AB)~27) 2002-2003: Subaru imaging (~25 nights - b,v,r,i,z=26/27) VLA (265 hours – 24 μJy) GALEX deep (200 ks, AB~25) XMM-Newton (800 ks – 10-15 cgs) 2004-2005: XMM-Newton (600 ks) VLT (540 hours) & Magellan (12+ nights) SPITZER-IRAC(200 hours - ~1 μJy) 2006: SPITZER-MIPS (200 hours - ~70 μJy) Chandra (1.8 Ms) Cosmos Survey 2deg2 (PI: N. Scoville) XMM-Newton PI: G. Hasinger http://cosmos.astro.caltech.edu ApJS special issue vol. 172 + MAMBO, CFHT, Bolocam and (future) others soft 0.5-2.0 keV medium 2.0-4.5 keV hard 4.5-10.0 keV The X-ray Universe 2008 http://www.astro.caltech.edu/cosmos/

  7. Relative sizes of X-ray surveys CDFN-CDFS 0.1deg2 Barger et al. 2003; Szokoly et al. 2004 -16 E-CDFS 0.3deg2 Lehmer et al. 2005 EGS/AEGIS 0.5deg2 Nandra et al. 2006 Flux 2-10 keV (cgs) -15 ELAIS-S1 0.5deg2 Puccetti et al. 2006 XMM-COSMOS 2 deg2 HELLAS2XMM 1.4 deg2 Fiore et al. 20003 Cocchia et al. 2006 Champ 1.5deg2 Silverman et al. 2005 -14 SEXSI 2 deg2 Eckart et al. 2006 -13 XBOOTES 9 deg2 Murray et al. 2005, Brand et al. 2005 Area (see Brandt & Hasinger 2005 review (ARA&A 43, 827)

  8. X-ray spectral analysis Fit statistic Cash-statistic with a binning of 1 count per bin: it recovers the input values better than 2 for faint sources (see also Tozzi et al. 2006 and Krumpe et al. 2008) Input models PL : powerlaw APL: powerlaw + intrinsic absorption at the redshift of the source Additional component to account for the photoelectric absorption due to the Galactic column density (NHGal~2.7 x 1020 cm-2, Dickey & Lockman 1990) Soft excess: black body model or a double powerlaw (pcfabs) FeK line: Gaussian centered at 6.4 keV rest-frame We have used the F-test to measure the significance for each spectral component (confidence threshold of 95%). 180 counts The X-ray Universe 2008

  9. X-ray zoo [0.5-2][2-4.5][4.5-10] keV APL APL+Fe PL APL+soft

  10. QSO-2: X-ray selection criteria • LXdeabs[0.5-10 keV]>1044erg/s • NH>1022 cm-2 121 QSO-2 Probably the largest sample of X-ray selected QSO-2 : 14 (Krumpe et al. 2008) 6 (Mainieri et al. 2002) 10 (Szokoly et al. 2004) 6 (Mateos et al. 2005) SDSS: 887 The X-ray Universe 2008

  11. QSO-2 : NH distribution The X-ray Universe 2008

  12. NH versus Redshift Statistical fluctuations in the X-ray spectrum can lead to spurious high values of NH at high redshift (e.g. Tozzi et al. 2006, Akylas et al. 2006). We find no trend of the NH values with redshift. The X-ray Universe 2008

  13. Compton-thick pexrav+gauss 25 arcsec ACS/HST z=0.1248 (SDSS spectrum) The X-ray Universe 2008

  14. Stacked X-ray spectrum • Only the rest-frame 2.1-10.1 keV band was used for each spectrum. • Spectral binning was designed to match a fixed rest-frame 200eV intervals. • The total accumulated counts are 4763.3 • Assuming =1.8 --> NH=(3.7± 0.6) 1022 cm-2 • EW(FeK)~200 eV The X-ray Universe 2008

  15. X-ray to optical flux ratios IAB=24 For IAB<24, 42% of the QSO-2 have spectroscopic redshifts. Above IAB=24, only photometric redshifts are available. 10% of the QSO-2 have X/O>10 The X-ray Universe 2008

  16. Photometric redshifts for AGN • = 0.017 Less than 10% of catastrophic errors • Improved templates, including hybrids of galaxy+AGN • Photometry from >30 bands (SDSS, Subaru including IB, CFHT, J, K, IRAC) Salvato et al., 2008 The X-ray Universe 2008

  17. ESO - PI S. Lilly The X-ray Universe 2008

  18. QSO-2 Redshift distribution • 34 spectroscopic redshifts (28%) : 17 from IMACS/Magellan, 13 from zCOSMOS VIMOS/VLT and 4 from DEIMOS/Keck. • 15 out of 34 (44%) do not show any sign of AGN activity from the optical spectra. zspec The X-ray Universe 2008

  19. X-ray vs L[OIII]5007 luminosity We measured L[OIII]5007 for 6 QSO-2 and 112 AGN: • X-ray selected QSO-2 have lower L[OIII] compared to optically selected ones. • Their L2-10/L[OIII] ratios are higher than opticaly seleted AGN : • <log(L2-10/L[OIII]>=0.6 for Seyfert-2 from Heckman et al. (2005) • Their L2-10/L[OIII] ratios are consistent with what observed for local sample of X-ray selected AGN: • <log(L2-10/L[OIII]>=2.2 from Heckman et al. (2005) The X-ray Universe 2008

  20. X-ray vs optical QSO-2: optical colors z~0.8 Stellar locus The X-ray Universe 2008

  21. QSO-2: X-ray vs MIR selection Stern’s wedge Lacy’s wedge MIR selection: good (86% of X-ray QSO-2 inside Lacy’s wedge, 75% of X-ray QSO-2 inside Stern’s wedge) …but not perfect :high contamination by starburst (all z) and elliptical (z>2) galaxies z=0-2 z=2-7 The X-ray Universe 2008

  22. Host galaxy morphology Zurich Estimator of Strutural Type (Scarlata et al. 2007, ApJS, 172, 406) • Five non-parametric diagnostics • (asymmetry A, concentration C, Gini coefficient G, 2nd order moment of the brightest 20% of galaxy pixels M20, ellipticity ) • Sersic index n • ZEST morphological type: • 1 Early type • 2 Disk • 2.0 Bulge dominated disk (n>2.5) • 2.1 … (1.25<n<2.5) • 2.2 … (0.75<n<1.25) • 2.3 Pure disk galaxy (n<0.75) • 3 Irregular http://www.exp-astro.phys.ethz.ch/ZEST/ Since optical radiation from QSO-2 is heavily obscured there is no significant contamination from the bright central source

  23. Host galaxy morphology ZEST morphological classification for 29 QSO-2 ELL SPIRALIRR B/D The majority the QSO-2 host galaxies are late type or irregular. Several of the irregular hosts can be described as undergoing merger activity or show tidal debris. • SDSS QSO-2 (Zakamska et al. 2006): • 6/9 de Vaucouleurs light profiles • 1/9 disk dominated • 2/9 marginal disk detection Comparison sample of 36000 galaxies morphologically classified The X-ray Universe 2008

  24. ACS/HST F814 W (5”x5”) 1.0 2.0 2.1 2.2 3.0 The X-ray Universe 2008

  25. Radio Loudness 1.4 GHz (2’x2’) Radio loudness defined in terms of the ratio of radio flux to broadband optical flux (e.g. Kellermann et al. 1989): assuming r~0.7 --> R~1.4 23/121 (~19%) radio loud QSO-2 R=log(f1.4GHz /fV) The X-ray Universe 2008

  26. Type-2 QSO: Spectral Energy Distribution [0.1-20 m] The mean SED of our QSO-2 is consistent with the typical SED of Type-2 AGN (Schmitt et al. 1997) and rule out Type-1 SED in which L rises by ~2 orders of magnitude below 1 m (Elvis et al. 1994). The X-ray Universe 2008

  27. Tyep-2 QSOs: stellar masses of the host galaxies Estimate of the stellar masses Bolzonella et al. 2008: SED fitting to the multi-band photometry in COSMOS (U,B,V,g,r,I,z,K,3.6,4.5): BC03/CB07/M05 libraries + Chabrier/Kroupa IMF+ smooth exponential SFHs The majority (75%) of QSO-2 have stellar masses above log M*~10.5MSUN. This is similar to the characteristic mass for obscured AGN (Kauffmann et al. 2003) and radio-loud AGN (Best et al. 2005) in the SDSS. It is also consistent with the more general result that the fraction of galaxies hosting AGN increases with the stellar mass ( e.g. Silverman et al. 2008). Comparison sample of 22157 galaxies with 0.7<z<3.7 The X-ray Universe 2008

  28. Tyep-2 QSOs: star formation rates of the host galaxies Estimate of the stellar masses Bolzonella et al. 2008: SED fitting to the multi-band photometry in COSMOS (U,B,V,g,r,I,z,K,3.6,4.5): BC03/CB07/M05 libraries + Chabrier/Kroupa IMF+ smooth exponential SFHs The host galaxies of QSO-2 have ongoing star formation higher that the comparison sample of galaxies. This is consistent with the host galaxies be manly late types or irregulars. 60% of QSO-2 have SFR in range 1-1000 MSUN/yr. Comparison sample of 22157 galaxies with 0.7<z<3.7 The X-ray Universe 2008

  29. Conclusions • We have selected a large (121) sample of QSO-2 based on their X-ray properties (NH>1022cm-2 & LX>1044 erg/s) on a wide redshift range: 0.6<z<3.7 • Their L2-10/L[OIII] ratios are higher than optically selected AGN-2. • Different selection methods (radio, mid-IR, optical, X-ray) of QSO-2 are affected by different selection effect therefore select different samples. • The majority the QSO-2 host galaxies are late type or irregular. • Several can be described as undergoing merger activity or show tidal debris. • The mean SED of our QSO-2 is consistent with the typical SED of Type-2 AGN. • The majority (75%) of QSO-2 host galaxies have stellar masses above log M*~10.5MSUNandhave ongoing star formation, <SFR>~100 MSUN/yr The X-ray Universe 2008

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