J/MNRAS/392/1509 Distribution of AGNs in galaxy clusters (Gilmour+, 2009)
The distribution of active galactic nuclei in a large sample of galaxy clusters.
Gilmour R., Best P., Almaini O.
<Mon. Not. R. Astron. Soc., 392, 1509-1531 (2009)>
=2009MNRAS.392.1509G 2009MNRAS.392.1509G
ADC_Keywords: Clusters, galaxy ; Active gal. nuclei ; X-ray sources
Keywords: galaxies: active - galaxies: clusters: general - X-rays: galaxies -
X-rays: galaxies: clusters
Abstract:
We present an analysis of the X-ray point source populations in 182
Chandra images of galaxy clusters at z>0.1 with exposure time >10ks,
as well as 44 non-cluster fields. The analysis of the number and flux
of these sources, using a detailed pipeline to predict the
distribution of non-cluster sources in each field, reveals an excess
of X-ray point sources associated with the galaxy clusters. A sample
of 148 galaxy clusters at 0.1<z<0.9 , with no other nearby clusters,
shows an excess of 230 cluster sources in total, an average of ∼1.5
sources per cluster. The lack of optical data for these clusters
limits the physical interpretation of this result, as we cannot
calculate the fraction of cluster galaxies hosting X-ray sources.
However, the fluxes of the excess sources indicate that over half of
them are very likely to be active galactic nuclei (AGN), and the
radial distribution shows that they are quite evenly distributed over
the central 1Mpc of the cluster, with almost no sources found beyond
this radius. We also use this pipeline to successfully reproduce the
results of previous studies, particularly the higher density of
sources in the central 0.5Mpc of a few cluster fields, but show that
these conclusions are not generally valid for this larger sample of
clusters. We conclude that some of these differences may be due to the
sample properties, such as the size and redshift of the clusters
studied, or a lack of publications for cluster fields with no excess
sources. This paper also presents the basic X-ray properties of the
galaxy clusters, and in subsequent papers in this series the
dependence of the AGN population on these cluster properties will be
evaluated.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 136 182 Final cluster sample split by morphological class
table4.dat 105 9833 Properties of sources detected in the cluster
fields
refs.dat 54 81 References
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- Mcl Morphological class code (1)
4- 27 A24 --- Cluster Cluster name (2)
29- 42 A14 --- ObsID Chandra observation identification number(s)
44- 45 I2 h RAh Right ascension (J2000)
47- 48 I2 min RAm Right ascension (J2000)
50- 53 F4.1 s RAs Right ascension (J2000)
55 A1 --- DE- Declination sign (J2000)
56- 57 I2 deg DEd Declination (J2000)
59- 60 I2 arcmin DEm Declination (J2000)
62- 65 F4.1 arcsec DEs Declination (J2000)
67- 70 A4 --- CCD ACIS detector or CCDs used
71- 75 F5.1 ks Exp Good exposure time, after filtering
(average over the selected chips)
77- 81 F5.2 fW/m2 FX ?=- Observed X-ray flux in 0.5-8keV band (4)
83- 87 F5.2 10+37W LX1 ?=- Rest frame 0.5-8keV luminosity (4)
89- 93 F5.2 10+37W LX2 ?=- Rest frame 0.1-2.4keV luminosity (4)
95- 98 F4.2 --- rchi2 ?=- Reduced chi2 value
100-104 F5.3 --- z Redshift
106-110 A5 --- r_z References for redshift, in refs.dat file
112 A1 --- n_z [1/3] Note on z (3)
114-118 F5.2 --- Excess Excess number of sources in the central 1Mpc
(compared to the prediction)
120-123 F4.2 --- E_Excess Error on Excess (upper value)
125-128 F4.2 --- e_Excess Error on Excess (lower value)
130-134 F5.2 [10-7W] Centre ? log luminosity of any source detected
within 25 kpc of the cluster centre
136 I1 --- n_Centre [2]? Note on Centre (3)
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Note (1): Morphological classes code explained in section 3.2.1:
0 = no cluster emission visible
1 = relaxed cluster (may be elliptical or have edges)
2 = disturbed cluster (disturbance must be joined to the cluster
by visible emission)
3 = merging cluster (double-peaked system with sub-cluster > 20% of
the main cluster)
4 = two clusters (a second cluster but not clearly associated)
1c = morphology 1 (relaxed cluster) with a small contamination (<20%)
2c = morphology 2 (disturbed cluster) with a small contamination (<20%)
hz = High redshift (proto)clusters
Note (2): Name of cluster in the NED. If more than one cluster name exists,
then the nearest is given. If there is no cluster within 2 arcmin,
then the nearest object name at the cluster redshift is given.
Note (3): Notes as follows:
1 = NED gives z=0.35, but the X-ray spectral data have a far better
fit with z=0.38
2 = this cluster has two X-ray point sources within 25kpc, which
overlap slightly. The second, at 10kpc, has log luminosity ∼43.72
3 = NED gives two redshifts, but only one is given in the paper which
NED refers to
Note (4): X-ray flux in 10-12erg/cm2/s, and luminosities in 1044erg/s
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 24 A24 --- Cluster Cluster name
26- 31 A6 --- --- [CXOGBA]
33- 48 A16 --- CXOGBA Source name (JHHMMSS.s+DDMMSS)
50- 51 I2 h RAh Right ascension (J2000)
53- 54 I2 min RAm Right ascension (J2000)
56- 59 F4.1 s RAs Right ascension (J2000)
61 A1 --- DE- Declination sign (J2000)
62- 63 I2 deg DEd Declination (J2000)
65- 66 I2 arcmin DEm Declination (J2000)
68- 71 F4.1 arcsec DEs Declination (J2000)
73- 79 F7.1 ct Ct Net Counts
81- 87 F7.2 aW/m2 FX X-ray flux (1)
89- 94 F6.1 --- Sig Source significance (2)
96-100 F5.2 --- HR ?=-1.00 Hardness ratio (3)
102-105 F4.2 --- e_HR ?=0.00 rms uncertainty on HR
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Note (1): assuming a spectrum with Γ=1.7; expressed in 10-15erg/cm2/s
Note (2): Sig=Counts/σbg, where σbg is he error on the
calculated background counts in the annulus
Note (3): Hardness ratio, (H-S)/(H+S), where H(2-8keV) and S(0.5-2keV) are
set to 0 for detections with significance <3 in that band.
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Ref Reference code
4- 22 A19 --- BibCode BibCode
24- 54 A31 --- Aut Author's name
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History:
* 06-Oct-2009 : From electronic version of the journal
* 06-May-2010 : Some names corrected in table2
(End) Patricia Vannier [CDS] 21-Aug-2009