J/MNRAS/436/275 Relaxation parameter of 2092 rich galaxy clusters (Wen+, 2013)
Substructure and dynamical state of 2092 rich clusters of galaxies derived
from photometric data.
Wen Z.L., Han J.L.
<Mon. Not. R. Astron. Soc., 436, 275-293 (2013)>
=2013MNRAS.436..275W 2013MNRAS.436..275W
ADC_Keywords: Clusters, galaxy ; Morphology
Keywords: galaxies: clusters: general
Abstract:
Dynamical state of galaxy clusters is closely related to their
observational properties in X-ray, optical and radio wavelengths. We
develop a method to diagnose the substructure and dynamical state of
galaxy clusters by using photometric data of Sloan Digital Sky Survey
(SDSS). To trace mass distribution, the brightness distribution of
member galaxies is smoothed by using a Gaussian kernel with a weight
of their optical luminosities. After deriving the asymmetry, the ridge
flatness and the normalized deviation of the smoothed optical map, we
define a relaxation parameter, Γ, to quantify dynamical state of
clusters. This method is applied to a test sample of 98 clusters of
0.05<z≲0.42 collected from literature with known dynamical
states and can recognize dynamical state for relaxed (Γ≥0)
and unrelaxed (Γ<0) clusters with a success rate of 94
percent. We then calculate relaxation parameters of 2092 rich clusters
previously identified from the SDSS, of which 28 percent clusters are
dynamically relaxed with Γ≥0. We find that the dominance and
absolute magnitude of the brightest cluster galaxies closely correlate
with dynamical states of clusters. The emission power of radio haloes
is quantitatively related to cluster dynamical state, beside the known
dependence on the X-ray luminosity.
Description:
We use the photometric data of the SDSS Data Release 8 (SDSS DR8,
Aihara et al., 2011ApJS..193...29A 2011ApJS..193...29A) to discriminate luminous member
galaxies and to estimate cluster richness and radius which will be
used in the quantification of cluster dynamical state.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 91 2092 Relaxation parameters of 2092 rich clusters in
the SDSS
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See also:
J/ApJS/183/197 : Galaxy clusters identified from the SDSS-DR6 (Wen+, 2009)
http://www.sdss3.org/dr8 : SDSS DR8 Home Page
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- --- [WHL]
5- 20 A16 --- WHL Cluster name (JHHMMSS.s+DDMMSS)
23- 31 F9.5 deg RAdeg BCG right ascension (J2000) (1)
34- 42 F9.5 deg DEdeg BCG declination (J2000) (1)
45- 50 F6.4 --- z [0.05/0.42] photometric or spectroscopic redshift
53 I1 --- f_z [0/1] 0 for photometric,
1 for spectroscopic redshift
56- 60 F5.2 mag rmag [13/20] BCG r magnitude (1)
63- 66 F4.2 Mpc R200 [1.2/2.3] Radius r200 of cluster
68- 73 F6.2 --- RL* [50/220] Cluster richness
75- 77 I3 --- N200 [30/178] Number of member galaxies within R200
80- 84 F5.2 --- Gamma Relaxation parameter Γ (2)
88- 91 F4.2 --- e_Gamma rms uncertainty on Gamma
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Note (1): BCG = Brightest Cluster Galaxy (central galaxy of the cluster)
Note (2): the relaxation parameter Γ is defined in section 3.6;
a positive value (Γ>0) indicates a relaxed cluster (a larger
Γ means a more relaxed cluster), whereas negative values of
Γ indicate unrelaxed clusters.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 19-Oct-2014