Issue |
A&A
Volume 430, Number 3, February II 2005
|
|
---|---|---|
Page(s) | 811 - 825 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361:20041375 | |
Published online | 26 January 2005 |
The spatial clustering of X-ray selected AGN and galaxies in the Chandra Deep Field South and North
1
Istituto Nazionale di Astrofisica (INAF) – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy e-mail: gilli@arcetri.astro.it
2
European Southern Observatory, Karl-Schwarzschild-Strasse 2, Garching, 85748, Germany
3
Istituto Nazionale di Astrofisica (INAF) – Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
4
Istituto Nazionale di Astrofisica (INAF) – Osservatorio Astronomico, via G. Tiepolo 11, 34131 Trieste, Italy
5
INFN, c/o Dip. di Astronomia dell'Università, via G. Tiepolo 11, 34131 Trieste, Italy
6
Institut d'Astrophysique de Paris, 98bis boulevard Arago, 75014 Paris, France
7
The Johns Hopkins University, Homewood Campus, Baltimore, MD 21218, USA
8
Associated Universities, Inc., 1400 16th Street NW, Suite 730, Washington, DC 20036, USA
9
Max-Planck-Institut für extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany
10
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
Received:
31
May
2004
Accepted:
22
September
2004
We investigate the spatial clustering of X-ray selected
sources in the two deepest X-ray fields to date, namely the 2 Ms Chandra Deep Field North (CDFN) and the 1 Ms Chandra Deep
Field South (CDFS). The projected correlation function ,
measured on scales
Mpc for a sample of 240
sources with spectroscopic redshift in the CDFN and 124 sources in the
CDFS at a median redshift of
is used to constrain the
amplitude and slope of the real space correlation function
. The clustering signal is detected at
high confidence (
) in both fields. The amplitude of the
correlation is found to be significantly different in the two fields,
the correlation length r0 being
Mpc in the
CDFS and
Mpc in the CDFN, while the correlation
slope γ is found to be flat in both fields:
in the CDFS and
in the CDFN (a flat
Universe with
and
is assumed;
Poisson error estimates are considered).
The correlation function also has been measured separately for sources
classified as AGN or galaxies. In both fields AGN have a median
redshift of
and a median 0.5-10 keV luminosity of
erg s-1, i.e. they are generally in the Seyfert
luminosity regime.
As in the case of the total samples, we found a significant difference
in the AGN clustering amplitude between the two fields, the best fit
correlation parameters being
Mpc,
in the CDFS, and
Mpc,
in the CDFN. In the
CDFN, where the statistics are sufficiently high, we were also able to
measure the clustering of X-ray selected galaxies, finding
Mpc and
.
Within each field no statistically significant difference is found
between soft and hard X-ray selected sources or between type 1 and
type 2 AGN.
After having discussed and ruled out the possibility that the observed
variance in the clustering amplitude is due to observational biases,
we verified that the extra correlation signal in the CDFS is primarily
due to the two prominent redshift spikes at
reported by
Gilli et al. ([CITE]).
The high (
Mpc) correlation length measured for the
X-ray selected AGN at
in the two Chandra Ms fields
is comparable to that of early type galaxies at the same redshift.
This is consistent with the idea that, at
, AGN with
Seyfert-like luminosities might be generally hosted by massive
galaxies.
Key words: galaxies: general / cosmology: large-scale structure of Universe / galaxies: Seyfert / X-rays: galaxies
© ESO, 2005
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