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X-ray selected Type-2 QSOs and their host galaxies

X-ray selected Type-2 QSOs and their host galaxies. Vincenzo Mainieri. with. A. Bongiorno, A. Merloni, M. Bolzonella, M. Brusa, M. Carollo, G. Hasinger, K. Iwasawa, L. Pozzetti, M. Salvato, J. Silverman, G. Zamorani, E. Zucca & COSMOS. Introduction. Why QSO-2?.

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X-ray selected Type-2 QSOs and their host galaxies

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  1. X-ray selected Type-2 QSOs and their host galaxies Vincenzo Mainieri with A. Bongiorno, A. Merloni, M. Bolzonella, M. Brusa, M. Carollo, G. Hasinger, K. Iwasawa, L. Pozzetti, M. Salvato, J. Silverman, G. Zamorani, E. Zucca & COSMOS

  2. Introduction Why 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 galaxy to AGN contrast ratio is maximized: “easier” to study the morphology of the host as well as its stellar mass and SFR. Caveat: UV light can be contaminated from scattered AGN light, SFR diagnostics (e.g. H, [OII]) excited by accretion power rather than young stars, etc.. Vincenzo Mainieri (ESO) QSO-2 and their host galaxies AGN9, Ferrara 26 May 2010

  3. Introduction QSO-2 selection band • 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, Lanzuisi et al. 2010, …) • 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 & 2009, Lanzuisi et al. 2009,…) Vincenzo Mainieri (ESO) QSO-2 and their host galaxies AGN9, Ferrara 26 May 2010

  4. QSO-2 sample X-ray spectra Sample selection 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) Selection criteria: LX>1044 erg s-1 NH>1022cm-2 146 QSO-2 Vincenzo Mainieri (ESO) QSO-2 and their host galaxies AGN9, Ferrara 26 May 2010

  5. QSO-2 sample Redshifts Spectroscopic follow-up z~0.8 VIMOS/VLT IMACS/Magellan Vincenzo Mainieri (ESO) QSO-2 and their host galaxies AGN9, Ferrara 26 May 2010

  6. QSO-2 sample Redshifts Redshift distribution • 34 spectroscopic redshifts from zCOSMOS (Lilly+09) and IMACS (Trump+08) • 112 photometric redshifts using gal+AGN templates (z=0.015,Salvato+09) Vincenzo Mainieri (ESO) QSO-2 and their host galaxies AGN9, Ferrara 26 May 2010

  7. QSO-2 sample BH masses and Eddington ratios Marconi & Hunt (2003): Log(MBH)=8.28+0.96(M*-10.9) Lbol=f(L[2-10 keV) from Hopkins+07 Vincenzo Mainieri (ESO) QSO-2 and their host galaxies AGN9, Ferrara 26 May 2010

  8. SED SED fitting : galaxy + AGN • Multi-band photometry: U, B, V, g, r, I, z, J, H, K, IRAC, MIPS-24 micron • Galaxies SED templates: Bruzual & Charlot (2003) + SFHs + Calzetti’s law • AGN SED template : Richards et al. (2006) • 0<E(B-V)<3: <NH>~5x1022cm-2 (assuming 1/3 of Galactic dust-to-gas) -> E(B-V)~3 • Chabrier IMF Vincenzo Mainieri (ESO) QSO-2 and their host galaxies AGN9, Ferrara 26 May 2010

  9. SED SED fitting : galaxy + AGN • 2 minimization comparing observed and template fluxes at the redshift of the QSO-2 • PRIORS • The maximum allowed age is the age of the Universe at the redshift of the source Vincenzo Mainieri (ESO) QSO-2 and their host galaxies AGN9, Ferrara 26 May 2010

  10. Host galaxy properties Stellar Mass Stellar Mass • Chabrier IMF • Parent sample of ~7000 galaxies selected in the same redshift range and X-ray flux limits of the QSO-2 sample. The fraction of galaxies hosting a QSO-2 increases with the stellar mass, consistently with what observed for the overall AGN population (e.g. Kauffmann et al. 03, Silverman et al. 2009) Vincenzo Mainieri (ESO) QSO-2 and their host galaxies AGN9, Ferrara 26 May 2010

  11. Host galaxy properties Star formation Host galaxies classification Photometric classification Separating red and blue galaxies (DEEP2, Cooper+07): U-B=-0.032(MB+21.52)+0.454-0.25+0.831 “Blue” QSO-2 : 50% “Red” QSO-2 : 50% Star formation activity classification Active: log(SSFR/Gyr-1) > -1 (75%) Quiescent: log(SSFR/Gyr-1) < -1 (25%) Vincenzo Mainieri (ESO) QSO-2 and their host galaxies AGN9, Ferrara 26 May 2010

  12. Host galaxy properties Star formation SFR-M* correlation Goal: compare the star formation in the QSO2 hosts with the tight correlation between SFR and M* of blue star-forming galaxies (e.g. Noeske et al. 2007; Daddi et al. 2007; Elbaz et al. 2007; Rodighiero et al. 2010). Vincenzo Mainieri (ESO) QSO-2 and their host galaxies AGN9, Ferrara 26 May 2010

  13. Host galaxy properties Star formation SFR-M* correlation Goal: compare the star formation in the QSO2 hosts with the tight correlation between SFR and M* of blue star-forming galaxies (e.g. Noeske et al. 2007; Daddi et al. 2007; Elbaz et al. 2007; Rodighiero et al. 2010). The hosts are evolving secularly (clues from dynamical studies of rest-frame optical/ UV selected high-redshift galaxies e.g., Förster Schreiber et al. 2006; Genzel et al. 2008; Shapiro et al. 2008) and star formation is not linked to a specific state of the AGNs. Vincenzo Mainieri (ESO) QSO-2 and their host galaxies AGN9, Ferrara 26 May 2010

  14. Host galaxy properties Co-evolution Co-evolution of QSO-2 and their hosts (Netzer 2009) L(FIR) from the SFR using the Kennicutt+98 relation: SFR(Msun yr-1)=L(FIR)/(5.8x1043 erg s-1) Vincenzo Mainieri (ESO) QSO-2 and their host galaxies AGN9, Ferrara 26 May 2010

  15. Conclusions • We found that X-ray selected Type-2 QSOs at z>0.8: • have 108<MBH<109.5, 0.01<Lbol/Ledd<1 • prefer to live in massive galaxies (M*>1010.5 MSun) • the majority of their host galaxies are actively forming stars (<SFR>~20 MSun/yr) at a rate comparable to z~1 blue star-forming galaxies or z~2 sBzK: secular evolution of the hosts Vincenzo Mainieri (ESO) QSO-2 and their host galaxies AGN9, Ferrara 26 May 2010

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