Luminous obscured quasars in the HELLAS2XMM survey: the Spitzer perspective Cristian Vignali Dipartimento di Astronomia, Universita`degli Studi di Bologna F. Pozzi, A. Comastri, C. Gruppioni, L. Pozzetti, M. Mignoli, C. Lari, G. Zamorani, M. Brusa & The HELLAS2XMM collaboration

2 The culprit … Who inspired this work … Radio-quiet quasars Radio-loud quasars Elvis et al. 1994

3 …and some recent results … Richards et al. 2006

4 Talk outline obscured AGN  The importance of obscured AGN: the X-ray view Spitzer  Why Spitzer? luminous, obscured quasars in the HELLAS2XMM  Sample selection: luminous, obscured quasars in the HELLAS2XMM survey and K S -band morphology of their hosts IRACMIPS data  A quick look at the Spitzer IRAC and MIPS data spectral energy distributions  Broad-band spectral energy distributions using IRAC+MIPS24 data: first results bolometric corrections, BH masses, and Eddington ratios  Physical properties of the X-ray selected obscured quasar population from HELLAS2XMM: bolometric corrections, BH masses, and Eddington ratios Mission impossible: all in 10 minutes!

5 The importance of obscured AGN: the X-ray view  A large fraction of the accretion-driven energy density in the Universe is obscured by dust and gas (e.g., Fabian 1999)  Ingredient of the X-ray background synthesis models (e.g., Comastri et al. 1995; Gilli, Comastri & Hasinger 2007) Type 2 quasars the high-luminosity, obscured AGN population (Type 2 quasars), expected on the basis of Unification schemes, only partially found  Obscured phase of the AGN growth linked to the host galaxy formation?

6 Why Spitzer?  The nuclear emission is re-processed in the IR band (by the dusty torus envisaged by the model?), less affected by extinction  Spitzer provides coverage over the μm wavelength range (and also at 70 and 160 μm is some cases)  IR emission important to compute the resulting bolometric luminosity of obscured, luminous AGN through their SEDs REQUIRED: removal of the galaxy contribution

7 Sample selection: obscured quasars from the HELLAS2XMM survey SAMPLE: HELLAS2XMM F 2-10 keV > erg cm -2 s -1 over 1.4 deg 2 Optically faint (R>24) sources with no optical identification  high X-ray-to-optical flux ratio (X/O>10) sources with indications of X-ray obscuration Mignoli et al ALL bright in the K S band All have R-K S >5 Extremely Red Objects (EROs), some are extreme Most have elliptical profiles, two are point-like (Mignoli et al. 2004) ISAAC K S -band follow-up

8 High X/O population unveiled also by Chandra e.g., SEXSI survey: Eckart et al Log (X/O)>1 ≈10-20% of the sources detected in the X-ray surveys have X/O>1

9 BLAGN EROs X/O>10 Lx= z=1.2 Point-like + steep PL SED Extended + galaxy-dominated SED (Civano et al., in prep.) a significant fraction of EROs is associated with X/O>10 sources EROs have larger X/O than broad-line AGN similarly, in the COSMOS survey… Lx=10 45 z=1.59 acs mips 24

10 What about the source redshifts? 0.8<z<2.4 6/8 sources Estimated redshift range: 0.8<z<2.4 (from photometry, Mignoli et al. ’04) – 6/8 sources 2/8 sources: secure spectroscopic redshifts from ISAAC (Maiolino et al. ’06) Maiolino et al LINER (X/O=52) QSO 1.9 (X/O=78) N H ~10 23 cm -2 + L 2-10 keV >10 44 erg/s Type 2 QSOs J H K S

11 K S -band images with 24 μm contours 40 arcsec All sources detected in IRAC & MIPS24 S(24 μm)= μJy

12 Spectral Energy Distribution: the modeling (I) Host galaxy Elliptical galaxy normalized to Ks + Torus emission Template from Silva et al. ’04 Bulge-dominated sources L bol =f(L X ; N H ) every source model normalized using its X-ray luminosity and N H values Silva et al. 2004

13 Bulge-dominated sources (in K S ): nuclear vs. host-galaxy emission NUCLEAR COMPONENT: not a SED fitting! normalized to X-ray observables: L X and N H normalized to X-ray observables: L X and N H Elliptical galaxy + nuclear component = match the data within a factor of 2-3 Nuclear comp. consistent with K S upper limits Nucleus starts dominating at ≈6 μm from Pozzi et al., WORK IN PROGRESS

14 Point-like sources (in the K S band) Extincted Type 1 quasar or red quasar template (from Polletta et al. 2006) normalized to 24 μm Extincted Type1 quasar NOT able to reproduce the data sharp decrease in the optical Good match using a red QSO template Spectral Energy Distribution: the modeling (II) from Pozzi et al., WORK IN PROGRESS

15 Bolometric correction and luminosity Bolometric luminosity = L BOL = k X  L 2-10 keV L BOL Sum the radiation directly linked to the accretion 1. Sum the radiation directly linked to the accretion L BOL = L X,INT + L OPT,UV REQUIRED: ►to remove IR bump (re-processed radiation) REQUIRED: ►to remove IR bump (re-processed radiation) to correct for gas/dust absorption in X-ray, optical, and UV ►to correct for gas/dust absorption in X-ray, optical, and UV Integration of the observed luminosities 2. Integration of the observed luminosities L BOL ≈ ∫ observed SED = L X,OBS + L IR,OBS our approach bolometric correction (≈35 in Type 1 QSOs from Elvis+ 94) BUT large dispersion in the broad-line QSO SEDs

16 from Urry & Padovani 1995 Corrections applied to the obtained face values to account for covering factor ↔ opening angle of the torus ↔ N(AGN2)/N(AGN1) in this L X range from Gilli+ 07 XRB models factor 1.5 covering factor ↔ opening angle of the torus ↔ N(AGN2)/N(AGN1) in this L X range from Gilli+ 07 XRB models factor 1.5 anisotropy ↔ only part of the anisotropy ↔ only part of the re-emission from the torus reaches the observer ≈ 10% re-emission from the torus reaches the observer ≈ 10% according to Silva templates

17 Median k X = L BOL /L 2-10 keV ≈ 27 Red QSO at z=2.08 Bolometric correction: preliminary results bulge-dominated point-like

18 Bulge and black hole masses K S -band flux mostly from the host galaxy L K M BH using the Marconi & Hunt (2003) local relation and assuming (M BH /M * ) z=1 = 2  (M BH /M * ) z=0 (Peng+ 06) Bulge-dominated sources ≈ 10 9 M  ≈ 10 9 M  Eddington ratio=L BOL /L EDD ≈ 0.06

19 BH masses: comparison with SDSS quasars Indications that:  these luminous obscured QSOs, residing in K S -luminous galaxies, have  these luminous obscured QSOs, residing in K S -luminous galaxies, have massive black holes SDSS data from McLure & Dunlop ’04

20 Eddington ratios: comparison with SDSS QSOs Indications that:  these very massive, X-ray luminous black holes at z ≈1-2 have z ≈1-2 have already passed their rapidly accreting phase  they have  they have reached their final masses with low accretion rates SDSS data from McLure & Dunlop ’04

21 if you have questions… I’m not sure I can answer … THE END

22 Abell2690_75 Abell2690_75 (Ell) R-K=6.3 z ph =1.30 Pks 0312_36 Pks 0312_36 (Ell) R-K=5.5 z ph =1.05 Pks 0537_91 Pks 0537_91 (Ell) R-K=5.1 z ph =0.90 Pks 0537_54 Pks 0537_54 (Ell) R-K>6.2 z ph =1.30 Pks 0537_111 Pks 0537_111 (Ell) R-K=6.8 z ph =1.45 Abell2690_29 Abell2690_29 (P) R-K=7.4 z sp =2.08 Pks 0312_45 Pks 0312_45 (P) R-K=5.7 z ph =1.65 BPM16274_69 BPM16274_69 (Ell) R-K=6.6 z sp =1.35 smoothed K S -band images

23 Spitzer observations T int Flux limit (5σ) IRAC (3.6/4.5/5.8/8.0  m ) 480 s  2.0  Jy (3.6 μm) MIPS 24  m 1400 s  100  Jy All sources detected in IRAC & MIPS24 Results All sources detected in IRAC & MIPS  m  Jy 24  m  Jy Detection of the obscured nuclear component? Detection of the obscured nuclear component?

24 24 micron data cleaning

25 X-ray vs. 24 μm flux

26 X-ray vs. 24 μm flux: the X/O>10 samples

27 Bulge-dominated sources (in K S ) NUCLEAR COMPONENT: not a SED fitting! normalized to X-ray observables: L X and N H normalized to X-ray observables: L X and N H Elliptical galaxy + nuclear component = match the data within a factor of 2 Nuclear comp. consistent with K S upper limits Nucleus starts dominating at 8.5 μm

28 Bulge and black hole masses K S -band flux mostly from the host galaxy estimate of the stellar mass M bulge assuming M star /L K =0.3-1 (valid for old stellar populations at z~0.9-2 and t~1-6 Gyr; Bruzual & Charlot ’03 ) Bulge-dominated sources massive host galaxies M star ≈ 10 11_ M  > ≈ 10 9 M  > ≈ 10 9 M  assuming the local L K -M BH relation (Marconi & Hunt ’ 03; see also Peng et al. ’ 06)

29 Summary  We have observed with Spitzer (  m) a sample of obscured X-ray selected AGNs. For almost all of them the optical & NIR emission is dominated by the host galaxy  All the sources have been detected in IRAC & MIPS24: dusty torus revealed?  Yes: SEDs well reproduced by 2 components: host elliptical galaxy + dusty torus emission (normalized to X-ray luminosity)  Bolometric luminosity & Black Hole masses derived.  Eddington ratios. "Fading" very massive Black Holes ( M  ) at high-z post rapidly accreting phase (L bol /L edd ~ )