Article

# Non-Gaussian velocity distributions - The effect on virial mass estimates of galaxy groups

Monthly Notices of the Royal Astronomical Society (Impact Factor: 5.52). 03/2011; 413. DOI: 10.1111/j.1745-3933.2011.01038.x

Source: arXiv

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**ABSTRACT:**The dynamical state of galaxy groups at intermediate redshifts can provide information about the growth of structure in the universe. We examine three goodness-of-fit tests, the Anderson--Darling (A-D), Kolmogorov and chi-squared tests, in order to determine which statistical tool is best able to distinguish between groups that are relaxed and those that are dynamically complex. We perform Monte Carlo simulations of these three tests and show that the chi-squared test is profoundly unreliable for groups with fewer than 30 members. Power studies of the Kolmogorov and A-D tests are conducted to test their robustness for various sample sizes. We then apply these tests to a sample of the second Canadian Network for Observational Cosmology Redshift Survey (CNOC2) galaxy groups and find that the A-D test is far more reliable and powerful at detecting real departures from an underlying Gaussian distribution than the more commonly used chi-squared and Kolmogorov tests. We use this statistic to classify a sample of the CNOC2 groups and find that 34 of 106 groups are inconsistent with an underlying Gaussian velocity distribution, and thus do not appear relaxed. In addition, we compute velocity dispersion profiles (VDPs) for all groups with more than 20 members and compare the overall features of the Gaussian and non-Gaussian groups, finding that the VDPs of the non-Gaussian groups are distinct from those classified as Gaussian. Comment: 11 pages, 9 figures, accepted for publication in ApJThe Astrophysical Journal 08/2009; · 6.73 Impact Factor -
##### Article: The RASS-SDSS galaxy cluster survey

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**ABSTRACT:**Solid observational evidences indicate a strong dependence of the galaxy formation and evolution on the environment. In order to study in particular the interaction between the intracluster medium and the evolution of cluster galaxies, we have created a large database of clusters of galaxies based on the largest available X-ray and optical surveys: the ROSAT All Sky Survey (RASS), and the Sloan Digital Sky Survey (SDSS). We analyzed the correlation between the total optical and the X-ray cluster luminosity. The resulting correlation of L_X and L_{op} shows a logarithmic slope of 0.6, a value close to the self-similar correlation. We analysed also the cluster mass to light ratio, by finding a significant dependence of M/L on the cluster mass with a logarithmic slope ranging from 0.27 in the i and r bands to 0.22 in the z band. Comment: proceedings of 'Multiwavelength mapping of galaxy evolution' conference held in Venice (Italy), October 2003, A. Renzini and R. Bender (Eds.), 2 pages, 1 figure03/2004; - [Show abstract] [Hide abstract]

**ABSTRACT:**Pages: 135Monthly Notices of the Royal Astronomical Society 01/2009; · 5.52 Impact Factor

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