G. Lodato (Università degli studi di Milano) New insights on the torus models from high-resolution SEDs of obscured high-z QSOs Margherita Bonzini Collaborators: M. Polletta (INAF-IASF Milano), D. Weedman (Cornell University, USA), L. Sargryan (Byurakan Astrphysical Observatory, Armenia) , G. Lodato (Università degli studi di Milano) AGN9, Ferrara, 24-27 maggio 2010

Outline Obscured Active Galactic Nuclei (AGN) at high redshift Sample and data Analysis: estimate of the host galaxy and AGN spectral energy distributions (SEDs) fit of the AGN SED with clumpy and smooth torus models Main results AGN9, Ferrara, 24-27 maggio 2010 Margherita Bonzini

Obscured Active Galactic Nucleai Black hole and accretion disk (optical-UV, X) Anisotropical dust structure (TORUS) (Infrared; IR) (e.g. Krolik & Begelman, 1988; Antonucci 1993) Unobscured AGN Obscured AGN AGN9, Ferrara, 24-27 maggio 2010 Margherita Bonzini

Obscured high-z AGN Why studying them? Some observational problems: Faint at optical and X-ray wavelengths The obscured AGN fraction decreases with increasing luminosity (?) (e.g. Simpson 2005, Akylas et al. 2006, Maiolino et al. 2007) Recently discovered by the Spitzer Space Telescope (e.g. Weedman et al., 2006; Lacy et al., 2007; Fiore et al., 2008; Polletta et al.,2008) Why studying them? To estimate the contribution to the total energy due to accretion processes To study AGN evolution To investigate the AGN and host galaxy interplay AGN9, Ferrara, 24-27 maggio 2010 Margherita Bonzini

Sample selection Obscured quasars at z ∼ 2 + HST images 30 sources From the Spitzer survey of the Boötes field (∼ 8 deg2) SELECTION CRITERIA: F24 μm > 0.8 mJy F[24 μm] /F[R] > 1000 With HST data (Bussmann et al. 2009, ApJ, 639, 750) Obscured quasars at z ∼ 2 (Weedman et al. 2006; Dey et al. 2008; Polletta et al. 2008) + HST images 30 sources AGN9, Ferrara, 24-27 maggio 2010 Margherita Bonzini

Objectives and method Objectives: characterization of the nuclear emission of z~2 quasars dust distribution: is it organized in a torus? is it described by current models? do dust properties vary with redshift and luminosity? Methods: nuclear and host galaxy optical-to-MIR SED reconstruction using photometric and spectroscopic data model comparison AGN9, Ferrara, 24-27 maggio 2010 Margherita Bonzini

10μm silicate feature in ABSORPTION Spitzer/IRS spectra Mean redshift: 2.17 ± 0.36 10μm silicate feature in ABSORPTION AGN9, Ferrara, 24-27 maggio 2010 Margherita Bonzini

Spectral energy distribution (SED) Host Galaxy AGN MIPS (24μm) IRS spectra (8-35μm ) IRAC (3.6, 4.5, 5.8, 8μm) HST (I, V, H) KPNO (Bw, R, I) (Ashby et al., 2009; Bussmann et al., 2009) Total Flux Separation of the host galaxy and AGN contribution to the total flux High-resolution HST data AGN9, Ferrara, 24-27 maggio 2010 Margherita Bonzini

Host galaxy and AGN contribution Estimate of the host galaxy SED using a starburst model library (Siebenmorgen & Krügel, 2007) CRITERIA: - agreements with HST data - model < total flux at all λ Host galaxy subtraction from the total flux Total Flux Host Galaxy AGN AGN SED The UV nuclear emission is absorbed by the dust and thermally re-emitted in the IR AGN9, Ferrara, 24-27 maggio 2010 Margherita Bonzini

Comparison with high-resolution MIR SEDs of local Seyfert 2 galaxies NGC 5506 Mrk 573 Circinus NGC 5506 Mrk 573 Circinus The nuclear emission from obscured AGNs with different L and z is similar NGC 5506 Mrk 573 Circinus NGC 5506 Mrk 573 Circinus (Ramos Almeida et al., 2009) AGN9, Ferrara, 24-27 maggio 2010 Margherita Bonzini

TWO SETS OF TORUS MODELS The dust is organized in clumps distributed in a toroidal structure around the black hole (Krolik & Begelman, 1988). TWO SETS OF TORUS MODELS CLUMPY tori (Nenkova et al., 2008) SMOOTH tori (Granato & Danese, 1994) Φ ~ 1 Φ ≪1 Φ = Vc/Vtot AGN9, Ferrara, 24-27 maggio 2010 Margherita Bonzini

Models are obtained solving the radiative transfer equations. SEDs library UV-to-IR SEDs with 2 components: Primary nuclear emission (transmitted and reflected) Dust thermal emission CLUMPY tori SMOOTH tori 7 PARAMETERS: dust grains properties spatial dust distribution optical depth inclination angle 6 PARAMETERS: number of clouds Models are obtained solving the radiative transfer equations. AGN9, Ferrara, 24-27 maggio 2010 Margherita Bonzini

Comparison between best-fit models SMOOTH tori CLUMPY tori SMOOTH models reproduce continuum + silicate absorption CLUMPY models are NOT able to reproduce the silicate absorption Smooth models better fit obscured QSO SEDs AGN9, Ferrara, 24-27 maggio 2010 Margherita Bonzini

SMOOTH tori parameters distributions Optically thick structures along the line of sight NO constraints on geometrical parameters AGN9, Ferrara, 24-27 maggio 2010 Margherita Bonzini

Torus size Possible explanation: compact torus + cold dust absorber Smooth torus models with a deep Si absorption correspond to spatially extended structures (~100 pc ). BUT: high-resolution measurements suggest compact structures (≲ 10 pc ) ( e.g. Tristram et al. 2007; Meisenheimer et al. 2007) Possible explanation: compact torus + cold dust absorber (see also Polletta et al. 2008, Martinez-Sansigre et al 2009) AGN9, Ferrara, 24-27 maggio 2010 Margherita Bonzini

Summary Selection of a sample of obscured quasar at z ~ 2 UV-to-MIR SED reconstruction using spectroscopic photometric measurements (with low and high resolution) Estimate of the host galaxy contribution using high spatial resolution HST data Characterization of the AGN SED with smooth and clumpy torus models AGN9, Ferrara, 24-27 maggio 2010 Margherita Bonzini

Possible cold dust component separated from the torus Conclusions IR continuum: similar in AGNs with different z and L well reproduced by both smooth and clumpy torus models Si absorption: Not reproduced by clumpy torus models but only by the smooth ones Importance of using both photometric and spectroscopic data to describe optical-to-IR AGN SEDs Smooth dust density structures better fit obscured QSO SEDs Deep Si absorption features correspond to extended structures (in contrast with high resolution measurements) Possible cold dust component separated from the torus AGN9, Ferrara, 24-27 maggio 2010 Margherita Bonzini

AGN9, Ferrara, 24-27 maggio 2010 Margherita Bonzini

AGN9, Ferrara, 24-27 maggio 2010 Margherita Bonzini

Conclusions The IR continuum of AGNs with different z and L is similar The clumpy model are not able to reproduce the deep Si absorption observed The SEDs are well reproduced by smooth tori Deep Si absorptions correspond to extended structures (in contrast with high resolution measurements) Possible cold dust component separated from the torus Importance of using both photometric and spectroscopic data to describe optical-to-IR AGN SEDs AGN9, Ferrara, 24-27 maggio 2010 Margherita Bonzini

Obscured AGN at high redshift and luminosity The fraction of obscured AGN decreases at high luminosities (from>80% at L~1042 erg/s to 38% at 1045 erg/s) (e.g. Hasinger et al. 2004, Simpson 2005, La Franca et al. 2005, Treister & Urry 2006, Akylas et al. 2006, Tozzi et al. 2006, Maiolino et al. 2007) Many high-z obscured quasars have been recently discovered by the Spitzer Space Telescope (e.g. Weedman et al., 2006; Lacy et al., 2007; Polletta et al.,2008) Dust properties vs luminosity Test of current torus models IMPRS workshop, Garching, Feb 9-11, 2010 Margherita Bonzini

Fitting the AGN SED Granato & Danese, 1994 Nenkova et al., 2002 METHOD: Minimization of the merit function: METHOD: BayesCLUMPY = code for the Bayesian analysis of AGN SEDs using clumpy models. (Asensio Ramos & Ramos Almeida, 2009, ApJ, 696, 2075) OUTPUT: probability distribution of the model parameters N = number of detections Fi = fluxes OUTPUT: Best fit values and probability distribution of the model parameters (See also e.g. Efstathiou & Rowan-Robinson 1995; van Bemmel & Dullemond 2003; Hönig et al. 2006) IMPRS workshop, Garching, Feb 9-11, 2010 Margherita Bonzini

Fitting results (1): MIR continuum & Si (10 μm) feature Granato & Danese Nenkova et al. IMPRS workshop, Garching, Feb 9-11, 2010 Margherita Bonzini

Fitting results (2) Granato & Danese Nenkova et al. Margherita Bonzini IMPRS workshop, Garching, Feb 9-11, 2010 Margherita Bonzini

Granato & Danese best-fit parameters About 2/3 of the objects require highly inclined tori with high optical depth IMPRS workshop, Garching, Feb 9-11, 2010 Margherita Bonzini