Obscured and unobscured growth of Supermassive Black Holes
Obscured and unobscured growth of Super-massive Black Holes Francisco J. Carrera, X. Barcons, J. Bussons, J. Ebrero, M. Ceballos, A. Corral (IFCA, CSIC-UC, Spain) & XMM-Newton Survey Science Centre (S. Mateos, M. J. Page, M. G. Watson, J. Tedds, R. Della Ceca. . . ) Extragalactic X-ray Surveys, Boston, November 6, 2006
Resolving the X-ray background: An XMM-Newton International Survey (AXIS)
Definition of the AXIS survey (Carrera et al 06) • 36 XMM-Newton target fields: – Galactic latitude |b|>20 deg – X-ray observations with EPIC-pn detector in FULL-FRAME-MODE – ~Avoided fields with bright and/or extended targets – Good time intervals > 10 ksec – Available early on in the mission • Solid angle ~4. 8 deg 2 • Using SAS v 6. 1. 1 to produce final source list and products: – Exposure and background maps – Source detection – Spectra and calibration matrices • Areas around target + OOT+ near the pn CCD gaps excluded • Own empirical sentitivity maps from detected source parameters • Very detailed source screening • Total of 1433 distinct X-ray sources with detection likelihood >15 in any of 4 bands (see below) Mrk 205 NGC 4291
Soft 0. 5 -2 ke. V XID 0. 5 -4. 5 ke. V X-ray source counts (XMM-Newton & Chandra & ASCA) Hard 2 -10 ke. V Ultrahard 4. 5 -7. 5 ke. V
The contribution to the X-ray background Deep Medium Shallow Surveys Medium surveys resolve the brightest 50% of the X-ray background
The XMM-Newton Medium Survey (XMS)
The XMS samples (Barcons et al. 07) • Subset of AXIS: – 25 fields chosen for follow-up: 3. 3 deg 2 – Flux limited in Soft, Hard and XID Name Band (ke. V) Flux limit # sources # identified 10 -14 cgs (unique) (fraction) Soft XMS 0. 5 -2 1. 5 210 (1) 200 (95%) -S Hard XMS 2 -10 -H 3. 3 159 (20) 132 (83%) XID XMS 0. 5 -4. 5 -X Ultrahard 4. 5 -7. 5 XMS-U 2. 0 284 (56) 261 (92%) - 70 (2) 60 (86%)
Optical identification of the XMS • Optical imaging: g, r, i (SDSS), Z (Gunn), mostly at the INT/WFC to r~23 -24 mag • Reliable & unique candidate counterpart in r/i for virtually all sources (< 5” or < 5 ) • Optical spectroscopy – 50% from AXIS programme (WHT, TNG, NOT): multifibre and long-slit spectroscopy – 20% from Calar Alto/3. 5 m long-slit spectroscopy – 15% from VLT/FORS 2 long-slit spectroscopy – A few from AAT/2 d. F, SUBARU/FOCAS, and others • Preliminary results from 2 XMM-Newton fields (~30 sources) in Barcons et al (2002)
The content of the XMS
Deep 10 m spec lim 4 m spec lim Medium Shallow
Breakdown of identified sources XMS-S Soft Broad-line AGN 75% (148/200) XMS-H Hard 63% (83/132) XMS-X XID 73% (190/261) XMS-U Ultrahard 65% (39/60) Narrow-line galaxies (AGN) 27% (35/132) 15% (39/261) 27% (16/60) 7% (9/132) 2% (3/132) 4% (10/261) 8% (20/261) 5% (3/60) 0% (0/60) 13% (27/200) Absorption line 4% galaxies+clust (8/200) Stars 8% (15/200)
Redshift distribution Soft Obscured population out to z~1 in Hard sample Hard Peak of QSO distribution (z~1. 5) well sampled.
Luminosities and redshifts QSO-2 @ z=2. 2 Soft QSOs All galaxies consistent with hosting AGN LX>1042 erg/s “Seyferts” Hard
Tips for statistical identification log(FHard/Fopt) 90% unobscured AGN ~90% Obscured AGN Stars HR 2
Obscured and Unobscured AGN
log(FSoft/Fopt) X-ray to optical ratio: a marker for obscuration? Soft • 5% of sources with f. X/fopt>10 • 30% of f. X/fopt>10 obscured AGN FX(10 -14 cgs) log(FHard/Fopt) FX/Fopt >10 • 15% of sources with f. X/fopt>10 • ~70% of f. X/fopt>10 obscured AGN Hard FX(10 -14 cgs)
E+S 0 r-i E+S 0 QSOs S+Irr Soft g-r QSOs S+Irr Optical colours 10% of QSOs are red # g-r Hard
Reddening r-i Fainter X-ray sources are redder? FHard(10 -14 cgs)
Optical versus X-ray “colours”: Hard g-r Harder sources are >90% obscured AGN Softer sources: Optically blue: unabsorbed AGN Optically red: mix of abs & unabs AGN Hard HR 2 Softer
X-ray absorption vs obscuration: not equivalent The XMS survey • 10% of type 1 AGN are absorbed (with NH<1022 cm-2) • >40% of type 2 AGN are absorbed The Lockman Hole survey • 15% (<30% at 3 ) of type 1 AGN are absorbed (with NH<1022 cm-2) • 80% (>50% at 3 ) of type 2 AGN are absorbed. But 5/28 are unabsorbed Mateos et al (2006) Mateos et al (2005)
Stacking analysis
Averaging X-ray spectra Corral et al. , in preparation AXIS+XMM-2 d. F NELGs • • Procedure still being tested Selecting X-ray spectra with >80 cts Unfolding with best fit Gal+Intrinsic abs. p. l. Correcting for Galactic NH AXIS+XMM-2 d. F De-redshifting BLAGN Renormalizing using flux in 2 -8 ke. V band Averaging in final bins (≥ 500 cts) Averaging AXIS: – BLAGN (200 sources) – NELG (43) • Much improved averaging AXIS+XMM-2 d. F (see Xu, Mateos): – BLAGN (549): =1. 95± 0. 02 Fe line @6. 5± 0. 2 ke. V EW=130± 60 e. V – NELG (113): =1. 53± 0. 02 Fe line @6. 6± 0. 4 ke. V EW=130± 100 e. V
Conclusions
• On-going work • Brightest 50% of the X-ray background dominated by AGN. • Unobscured accretion dominates, but increasingly important contribution from obscured objects. • X-ray absorption and optical obscuration not equivalent: – – 10% 15% 25% 10% of of type 1 AGN are X-ray absorbed type 2 AGN are not X-ray absorbed f. X/fopt>10 hard X-ray sources are type 1 AGN X-ray selected type 1 AGN have red colours • Even at medium fluxes, an important fraction of the X-ray sources have optically faint and red optical counterparts. • Most un. IDed objects faint (r/i>21. 5) and extended: NELGs • Preliminary results from average spectra show Fe lines in both BLAGN and NELGs
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