x-ray selected type-2 qsos and their host galaxies vincenzo mainieri with a. bongiorno, a. merloni,...

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

Vincenzo Mainieri (ESO) QSO-2 and their host galaxies AGN9, Ferrara 26 May 2010

Introduction

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)

Why QSO-2?

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..


Introduction

• 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<0.83MB<-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,…)

QSO-2 selection band


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


QSO-2 sample Redshifts

Spectroscopic follow-up

VIMOS/VLT

IMACS/Magellan

z~0.8


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)


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


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


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


Host galaxy properties Stellar Mass

Stellar Mass

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)

• Chabrier IMF

• Parent sample of ~7000 galaxies selected in the same redshift range and X-ray flux limits of the QSO-2 sample.


Host galaxy properties Star formation

Host galaxies classification

Photometric classificationSeparating 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%)



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).



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.


Host galaxy properties Co-evolution

Co-evolution of QSO-2 and their hosts

L(FIR) from the SFR using the Kennicutt+98 relation: SFR(Msun yr-1)=L(FIR)/(5.8x1043 erg s-1)

(Netzer 2009)


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

x-ray selected type-2 qsos and their host galaxies vincenzo mainieri with a. bongiorno, a. merloni,...

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