The 2Ms Chandra Deep Field-North

Introduction to the X-ray background D. M. Alexander (IoA), Diversity of X-ray selected sources L. L. Cowie (IfA), and C. Vignali (Bologna) AGNs and binary AGNs in submm galaxies 2 Ms CDF-N (and 1 Ms CDF-S) catalogs are in Alexander et al. (2003) See http://www.astro.psu.edu/user/niel/hdf-chandra.html

Introduction to the X-ray background

Cosmic Background Radiation

CXB: first background discovered (e.g., Giacconi et al. 1962)

The Cosmic X-ray Background (Comastri et al. 1995)

G

~1.4

0.5-10.0 keV ROSAT: ~70% of 0.5-2.0 keV b/gd resolved ASCA/SAX: ~30% of 2-10 keV b/gd resolved Finding mostly unobscured AGNs

(G~2.0)

The New Generation of X-ray Observatories Chandra Weisskopf et al. (2000) Launched July 1999 ~0.1-10.0 keV band sensitivity Unsurpassed 0.”5 spatial resolution 4 mirrors (1145 cm 2 ) 16.’9x16.’9 field of view XMM-Newton Jansen et al. (2001) Launched December 1999 ~0.1-12.0 keV band sensitivity 5” spatial resolution 58 mirrors (4300 cm 2 ) ~30’ field of view

The 2Ms Chandra Deep Field-North

Deepest X-ray survey in 0.5-8.0 keV band See also talks by Comastri, Georgantopoulos, Green, and Mainieri ~50 times deeper than deepest ROSAT survey ~250 times deeper than deepest ASCA survey Alexander et al. (2003) Deep enough to detect mod.lum starbursts at z~1 and mod.lum AGNs at z~6

“True” color image 0.5-2.0 keV 2.0-4.0 keV 4.0-8.0 keV (447 arcmin 2 ) HDF-N 1.945 Ms ACIS-I exposure 80-95% of 0.5-2 keV 70-90% of 2-8 keV

Alexander et al. (2003)

20 observations spanning 27 months

Scores on the Doors… One count detected every 6 days!

503 main independent sources +78 supplementary sources +6 extended sources Alexander et al. (2003) Bauer et al. (2002)

“True” color image 0.5-2.0 keV 2.0-4.0 keV (447 arcmin 4.0-8.0 keV 2 ) 1.945 Ms ACIS-I exposure SCUBA (sub-mm) HDF-N GOODS survey (ACS+SIRTF) ISOCAM (mid-IR) Deep optical-near-IR, and radio observations over whole field ~1000 spectroscopic redshifts 80-95% of 0.5-2 keV 20 observations

Alexander et al. (2003)

70-90% of 2-8 keV spanning 27 months

HST ACS 3/5 Epochs 18000x24000 pixels

3” 6”

F850LP (z) F775W (i) F606W (V) F435W (B) (ACS+SIRTF)

2.5”

P.I.: M. Giavalisco Created by A. Koekemoer and Z. Levay Astrometry by S. Casertano and R. Hook Verification by M. Giavalisco, H. Ferguson, A. Koekemoer, M. Dickinson, N. Grogin, S. Ravindranath, T. Dahlen, and GOODS/ACS team

Source Redshifts

Optical and Redshift Data Optical data from the Subaru telescope (Capak et al. 2003) 503 Chandra sources (56% with redshifts) Spec-z are challenging even for 8-10m telescopes Spec-z Redshifts mostly from the Keck telescope (Barger et al. 2003)

Redshift Distribution Barger et al. (2003) Spec-z Phot-z Majority of the sources lie at low-z; taking account of incompleteness is unlikely to significantly raise the z-peak

Peaks in the Redshift Distribution Barger et al. (2003) Optical cluster (Dawson et al. 2001) and infrared redshift peak at z~0.85

FRI radio galaxy (Richards et al. 1999), and extended X-ray emission (Bauer et al. 2002) at z~1.01

Biasing due to large scale structure? See also Gilli et al. (2003) Similar peaks seen in the optical and infrared (e.g., Cohen et al. 2000)

Diversity of X-ray selected sources AGNs, starbursts, and galaxies

X-ray-to-optical flux ratio diagram Broad range of optical magnitudes at faint X-ray fluxes could suggest a variety of different source types

Barger et al. (2002) AGN source diversity Alexander et al. (2001) AGN source density ~5000 deg -2 : ~10 times higher than the deepest optical surveys Barger et al. (2002) Barger et al. (2002) X-rays provide a very efficient route to identifying AGNs and are relatively insensitive to absorption

AGN source diversity Bauer et al., in prep.

Column density distribution determined via X-ray spectral analyses of 320/503 bright sources Many obscured AGNs are detected and the 183 fainter sources appear to be heavily obscured Very few Compton-thick AGNs (~30: Alexander et al. 2003)

AGN source diversity Only a few obscured QSOs are identified: they are either rare or mostly exist at fainter fluxes Column density distribution determined via X-ray spectral analyses of 320/503 bright sources Many obscured AGNs are detected and the 183 fainter sources appear to be heavily obscured Very few Compton-thick AGNs (~30: Alexander et al. 2003)

Starbursts and Normal galaxies Hornschemeier et al. (2003) Bauer et al. (2002) Normal Galaxies Starburst Galaxies Evidence for X-ray detected galaxies: infrared, radio, optical, and X-ray (e.g., Alexander et al. 2002; Bauer et al. 2002; Hornschemeier et al. 2003)

Starbursts and Normal galaxies Hornschemeier et al. (2003) Normal galaxies may dominate the source counts at very faint X ray fluxes (Miyaji & Griffiths 2002; Hornschemeier et al. 2003)

Stacking sources below the detection limit This technique has been successful in detecting average X-ray emission from these other source populations: EROs (Alexander et al. 2002; Brusa et al. 2002) Normal galaxies out to z~1 (Hornschemeier et al. 2002; Nandra et al. 2002) Brandt et al. (2001) See Brusa talk for more Stacking 24 individually undetected z=2-4 Lyman-break galaxies, an overall X-ray detection was achieved! Average X-ray luminosity is comparable with that of a luminous starburst galaxy (e.g., NGC 3256)

Contributions to the cosmic background

15 micron (IR) background (~70%): ~15% from AGNs (Alexander et al. 2002; Fadda et al. 2002) ~85% from starbursts/galaxies 0.5-8.0 keV background (~70-95%): Close to 100% from AGNs (many obscured) 2-5% from starbursts/galaxies 850 micron (submm) background: ~15% from AGNs (Barger et al. 2001) but many bright submm galaxies host an AGN (Alexander et al. 2003) ~85% from starbursts/galaxies

Accretion Activity in the Universe AGN evolution

The cosmic evolution of AGNs

Cowie et al. (2003) AGN evolution is a function of the luminosity of the AGN => moderate-luminosity activity peaks at lower-z than high-luminosity activity (see also Fiore et al. 2003; Hasinger et al. 2003)

The cosmic evolution of AGNs

Less high-z AGNs than many models predicted; too few to re ionise the Universe (see also Alexander et al. 2001 and Cristiani et al. 2003) See Brandt talk for properties of z>4 AGNs Cowie et al. (2003) CDF-N Barger et al. (2003) SDSS AGN evolution is a function of the luminosity of the AGN => moderate-luminosity activity peaks at lower-z than high-luminosity activity (see also Fiore et al. 2003; Hasinger et al. 2003)

X-ray detected submm sources AGNs in dusty starburst galaxies

Moderately deep Chandra surveys reported little overlap with the submm source population (e.g., Fabian et al. 2000; Severgnini et al. 2000; Hornschemeier et al. 2000, 2001; Barger et al. 2001)… What is the picture for a deep Chandra survey?

AGNs in submm galaxies 850 micron SCUBA image Borys et al. (2003) 13 S/N>4 SCUBA galaxies detected with f(850um)>5 mJy (Borys et al. 2003)

AGNs in submm galaxies 850 micron SCUBA image Borys et al. (2003) 7 (54%) of the sources are X-ray detected (Alexander et al. 2003)

AGNs in submm galaxies 850 micron SCUBA image At least 5 are AGNs (38% of bright submm galaxies) => almost all appear to be Compton-thin moderate luminosity AGNs Given that only ~50% of local AGNs are Compton thin (i.e., Risaliti et al. 1999), most (if not all) bright submm galaxies may contain an accreting SMBH AGNs are not luminous enough to power the submm emission Borys et al. (2003) 7 (54%) of the sources are X-ray detected (Alexander et al. 2003)

Binary AGNs?

Komossa et al. (2003) ~20kpc NGC6240 ~1kpc Alexander et al. (2003) 2/7 (30%) submm galaxies with close X ray pairs (<3”) vs 5/193 (3%) over whole field (see also Smail et al. in prep) ~20kpc Alexander et al. (2003) This phenomena seems to be more closely linked to submm galaxies

Future Directions

Deeper vs Wider 1.

2.

3.

4.

Why Go Deeper?

Discovery space (still approx. photon limited) Detect more Compton-thick AGNs Improve X-ray spectral analysis Detect more galaxies 1.

2.

3.

4.

Why Go Wider?

Detect rarer source types (e.g., obscured QSOs, high-z AGNs) Improve statistics on AGN evolution/luminosity function Trace both obscured and unobscured AGN evolution Uncover extent of large-scale structure (i.e., redshift peaks)

Summary

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Resolved close to 100% of the 0.5-8.0 keV background:

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most sources lie at at z<1

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peaks in z-distribution suggest large-scale structure effects

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Broad variety of source types are detected:

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optically (and X-ray) obscured and unobscured AGNs

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starburst and normal galaxies

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stars, galaxy groups and clusters

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stacking analyses provides constraints on sources below detection limit

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Efficient (and mostly absorption independent) AGN selection:

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AGN source density >10 times larger than in optical ( ~5000 deg -2 )

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but few Compton thick AGNs are detected (further AGNs to be found?)

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Mod-lum AGNs dominant at low-z, contrary to high-lum AGNs

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Many (all?) bright submm galaxies contain an AGN/binary AGN For all papers and data products (CDF-N and CDF-S): http://www.astro.psu.edu/user/niel/hdf-chandra.html