X-ray view of the most obscured QSOs at high redshift

Chiara FeruglioCNRS - CEA, Saclay

IRAM - Institut de RadioAstronomie Millimetrique 

thanks to:Daddi, Fiore, Piconcelli, Alexander, Malacaria, Puccetti et al.

IXO science meeting, Roma, 14 March 2011

Why highly obscured, Compton thick, high luminosity AGN are so important:They can be witnesses of a crucial phase in the AGN/galaxy

coevolutionary sequence, an evolutionary scenario led by galaxy interactions (& mergers):

• Obscured, rapid growth of both central SMBH and galaxy (high SF)• Onset of AGN feedback, through powerful winds

• AGN power heats and expells the ISM in the disk, quenching star-formation [Silk & Rees 98, Di Matteo+ 05, Croton+ 06, King 05 Hopkins +08, Somerville+ 08, Menci +08, Catteneo+08]

galaxy-galaxy interactions major mergers

The phase of highly obscured, intrinsecally luminous QSO hosted in powerful SF galaxies

should be the best to catch AGN feedback

A spectacular example: QSO feedback in Mrk 231

The nearest (z=0.042, 187Mpc) QSO • Lbol=2 1046 erg/s • highly obscured, NH~1024 cm-2 • loBAL with winds arising from the BLR • expanding bubbles on kpc scales seen by HST• hosted in a ULIRG with SFR ~200 MSun/yr (late stage merging system)

Braito+2004

Lipari+09

Goal : detect the outflow of the cold molecular gas in the QSO host

QSO feedback revealed in Mrk 231

CO(1-0) @115.2712 GHzNarrow component +low surface brightness broad component with wings extending out to +-800 km/s(FWZI = 1500 km/s).

Wings are spatially resolved and extended on 1.2 kpc scales.

Map of Blue wing Map of Red wing

OUTFLOW RATE dM(H2)/dt = 700 M ⊙ /yr

SFR ~ 200M⊙ /yr

Kinetic energy of outflowing gas: E =1.2 1044 erg/s = ~1% LBol (2 1046 erg/s)expected for AGN radiation driven shock-wave expanding in the ISM (Lapi+05)

CO(1-0) CO(1-0)Broad

IRAM-PdBI detection of broad CO(1-0)

(Feruglio et al. 2010)

Mrk 231 massive, Kpc-scale molecular outflow

The P-Cygni profiles of the OH 119 μm and 18OH 120 μm OH 79 μm blue-shifted lines confirm the OUTFLOW with vel ~1400 km/s.

Confirmed by Herschel... (Fischer et al. 2010)

... and recently confirmed by IFU spectroscopy (Rupke+2011)Neutral gas absorption traces 2-3 Kpc scale outflow with v ~ 1100 km/s powered by the AGN

Are SMBH/galaxy rapid obscured growth and QSO feedback

common at z~2 ? peak of AGN & SF activity

Gilli et al. 2007

Finding highly obscured & Compton thick AGNs is extremely challenging because of Obscuring column NH > 1024 cm-2

but crucial for: • the hard X-ray background • feedback on SF • BH mass-bulge relation

Recent discovery of very large gas reservoirs in high-z massive galaxies support rise in average NH (hence, in very obscured system) (Daddi et al. 2009, Tacconi et al. 2010)

Finding the most obscured, missing BH at high z

Highly obscured AGN

Finding the most obscured, missing BH

IR selection of candidate highly obscured AGN, missed by hard X-ray surveys:• objects with mid-IR excess (Daddi+07)• obj bright in the mid-IR and faint in the optical (DOGs, Fiore+08,09, Martinez-

Sansigre 2005)• Power-law SED in the IR (Lacy+2004, Polletta+2006, Donley+2008)

X-ray stacking shows that a large fraction hosts highly obscured AGN.

However, only X-ray observations can confirm the AGN nature of these sources, by estimating obscuration and the intrinsic AGN

power.mid-IR excess

power-law SEDDOGs

Guainazzi+2005 Fukazawa+2010

Circinus galaxy

Fe Kwith high EW (>1 keV) on flat continuum is the hallmark of Compton thick obscurationNH > 1.5 1024 cm-2

Compton thick AGN in the local universe

Only few dozen objects known even locally

Deep X-ray observations confirm a few CThick at high z with o Fe K 6.4 keV with EW > 1 keVo flat spectrum

Compton thick AGN in the distant universe

a type 2 QSO at z=3.71 in CDFS (Norman et al. 02; )

Confirmed recently by Comastri et al. 2011(XMM survey of CDFS, 3 Ms)

Gilli+2011 @z = 4.76

Georgantopoulos+09, 6 CThick in CDFN, Fe K stacked

Discovery of CThick QSO in two BzK galaxies at z~2.5-3

Feruglio, Daddi, Fiore, Alexander, Piconcelli & Malacaria, 2011

Based on the 4 Msec Chandra data of CDFSBzK4892 zspec=2.578 Fe Kα (6.4 keV) > 4σ detectionEW=2.3 -0.6

+1 keV

EW(Fe Kα) = 2.3 keV ==> COMPTON THICK QSO , NH>>1024 cm-2

L(2-10 keV) ~1044.5 erg/s, most likely 1045 erg/s

derived from Fe Kα, mid-IR , optical lines

zspec=2.578

BzK8608 zphot=2.9

Fe Kα 3σ detection with EW=1.2 ± 0.4 keV

Compton-thick QSO, NH> a few 1024

Lx ~ 1044 erg/s

Discovery of CThick QSO in two BzK galaxies at z~2.5-3 Feruglio, Daddi, Fiore, Alexander, Piconcelli & Malacaria, 2011

zphot=2.9

Fe K redshift constraint vs optical redshift constraint

FeK might be a useful tool (for future missions)to measure redshifts of the most obscured systems

z/1+z ~ 0.02 (1)

spectro-z photo-z

Extreme mid-IR excess (x170), DOG, F(24um) = 591 uJy U-band drop-out SFR ~70 MSun/yr from UV SFR ~1100 MSun/yr from Radio (VLA) SFR ~500 MSun/yr from Apex-Laboca 870 um detected by Herschel PACS+Spire ACS morphology suggests merger, 2 blobs

Mid-IR excess (x6), U-band drop-out SFR ~70 MSun/yr from UV SFR ~300 MSun/yr from Radio no Herschel detection

ACSACS

The SF host galaxies of Compton thick QSOs

Highly obscured QSO hosted in highly star forming, dust obscured galaxies

ERS+GOODS-MUSIC survey in the CDFS 4Msec exposure Compton thick AGN at z > 3

Large fraction of highly obscured AGN at z > 3 (3/17) in CDFS 4Ms ERS survey (Fiore+2011). Fraction of CThick~17% at F(2-10)~0.3-3 10-16 cgsThis is already ~ total CT fraction predicted by GCH2007. Fraction of CT at high-z may be higher than predicted before (similar result obtained by Gilli+ 2011)

E537 L(2-0keV)=1043.8 erg/sE1577 L(2-10keV)=1043.6 erg/sE8579 L(2-10keV)=1043.5 erg/s

20-40keV20-40keV ERS (FF+11)ERS (FF+11) GCH 2007 GCH 2007

Treister 2009Treister 2009

2-10 keV Chandra/XMM2-10 keV Chandra/XMM

Fiore+2011

Gas-to-dust ratio of the absorbing matter ~ 1/100-1/1000 of the Galactic value.

Compact absorber <1 pc smaller than dust sublimation radius (see eg. Shi+2006) or smaller dust content

ERS+GOODS-MUSIC survey in the CDFS 4Msec exposure

Shi+2006

1/1001/1000

Filled:Point-likeOpen: extended

Density of CThick AGN

• @z=1.4-3 and L(2-10keV) > 1044 erg/s: 3E-6 Mpc-3 ~1 in 80 arcmin2 • @z >3 and L(2-10keV) > 10 43.5 : ~ 1 in 25 arcmin2

In WFI 18x18 arcmin FOV it means between 2-10 obj. per field

Simulated 100 and 500ks IXO/WFI spectra of ERS 537 and ERS 1577, assuming Fe Ka 6.4 keV, Fe He-like 6.7 keV and Fe H-like 6.9 keV as in NGC1068

NGC1068 Matt+2004

The IXO view of CThick QSOs

Simulated spectra of BzK4892 at z=2.578: - WFI in 100 ks make redshift of BzK-like objects z / 1+z ~ 0.01 (1- XMS: detects emission lines only: search for sharp concentration of photons in deep XMS fields

A survey of 20 50/200ks fields would yield ~40 CThick with L(2-10keV) > 1044 erg/s at z<3 and ~160 with L(2-10keV)>1043.5 erg/s with spectra of quality similar or better to that available today with Chandra multiMsec exposures.Surprises from search of photon concentration in energy in deep XMS pointings

• Luminous CT AGN can be witnesses of crucial phase in AGN/galaxy co-evolution: onset of AGN feedback

• Chandra provides today the best evidence for luminous CThick AGNs at high-z

• Tip of the iceberg: Lx ~ 1044 erg/s for BzK4892 Strong Fe Ka (30 counts in the line, 80 total in 4Msec)

• Lx>1043.5 erg/s CThick AGN and/or higher z are fainter but still feasible with Chandra (Gilli+2011, Fiore+2011). They are probably more common, 1-2 per WFI FOV.

Conclusions