J/other/NewA/27.41 Velocity distributions in galaxy clusters (Sampaio+, 2014)
Velocity distributions in galaxy clusters. How to combine different
normality tests.
Sampaio F.S., Ribeiro A.L.B.
<New Astron., 27, 41-55 (2014)>
=2014NewA...27...41S 2014NewA...27...41S
ADC_Keywords: Clusters, galaxy ; Velocity dispersion
Keywords: Galaxy clusters
Abstract:
We study 416 galaxy systems with more than 7 members selected from the
2MASS catalog. We applied five well known normality tests to the
velocity distributions of these systems to distinguish Gaussian and
non-Gaussian clusters. Using controlled samples, we estimated type I
and II errors for each test. We verified that individual tests
minimize the chances of classifying a Gaussian system as non-Gaussian,
while the Fisher's meta-analysis method, a procedure to combine
p-values from several statistical tests, minimizes the chances of
classifying a non-Gaussian system as Gaussian. Taking the positive
elements of each method and also including a modality analysis of the
velocity distribution, we defined objective criteria to split up the
sample into Gaussian and non-Gaussian clusters. Our analysis indicates
that 50-58% of groups have Gaussian distribution, a lower fraction
than that we found using individual normality tests, 71-87%. We also
found that some properties of galaxy clusters are significantly
different between Gaussian and non-Gaussian systems. For instance,
non-Gaussian clusters have larger radii and contain more galaxies than
Gaussian clusters. Finally, we discussed the importance of choosing
the adequate methodology to classify galaxy systems from their
velocity distributions and also the dependence of the results on the
criteria used to identify clusters in galaxy surveys.
Description:
We study 416 galaxy systems selected from the 2MASS (Two Micron All
Sky Survey Extended Source Catalog - Crook et al. (2007, Cat.
J/ApJ/655/790)). We used just groups with more than 7 members to avoid
severe sample size effects
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
appena.dat 49 416 Complete results for the classification of Gaussian
and non-Gaussian groups taking galaxies within R200
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See also:
J/ApJ/655/790 : Groups of galaxies in 2MASS survey (Crook+, 2007)
Byte-by-byte Description of file: appena.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- Group [LDC HDC] Low or High Density Contrast group
5- 8 I4 --- ID [6/1260] Group number (1)
10- 12 I3 --- N200 [8/300] Number of galaxies within R200
14- 19 F6.2 km/s sigma [43/950] Velocity dispersion σ
21- 25 F5.3 Mpc R200 [0.1/3] Virial radius, R200
27- 31 F5.2 [Msun] logM200 [11.2/15.3] Mass of galaxies within R200
33- 37 F5.2 mag m12 [-4.3/0] Magnitude difference between the first
and second brightest galaxies
39- 43 F5.3 Mpc-3 v200 [0.6/4.2] Number density of galaxies
(in N200*Mpc-3 unit)
45 I1 --- DP [0/1] Gaussian (0) or non-Gaussian (1) group
according to the DP test
47 I1 --- MA [0/1] Gaussian (0) or non-Gaussian (1) group
according to the metanalysis
49 I1 --- mod [0/1] Gaussian (0) or non-Gaussian (1) group
according to the modality analysis
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Note (1): Identification number in the Crook et al. 2007 (J/ApJ/655/790)
table; <[CHM2007] LDC NNNN> or <[CHM2007] HDC NNNN> in Simbad
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 23-Mar-2015