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J/other/NewA/27.41 Velocity distributions in galaxy clusters (Sampaio+, 2014)
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Beginning of ReadMe :J/other/NewA/27.41 Velocity distributions in galaxy clusters (Sampaio+, 2014)
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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
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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