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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

SPIDER - IX. Classifying galaxy groups according to their velocity distribution

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Ribeiro, A. L. B. [1] ; de Carvalho, R. R. [2] ; Trevisan, M. [2] ; Capelato, H. V. [2, 3] ; La Barbera, F. [4] ; Lopes, P. A. A. [5] ; Schilling, A. C. [1]
Total Authors: 7
[1] Univ Estadual Santa Cruz, Lab Astrofis Teor & Observac, BR-45650000 Ilheus, BA - Brazil
[2] MCT, Inst Nacl Pesquisas Espaciais, Sao Jose Dos Campos - Brazil
[3] Univ Cruzeiro Sul, Nucleo Astrofis Teor, Sao Paulo - Brazil
[4] INAF Osservatorio Astron Capodimonte, Naples - Italy
[5] Univ Fed Rio de Janeiro, Observ Valongo, BR-21941 Rio De Janeiro - Brazil
Total Affiliations: 5
Document type: Journal article
Source: Monthly Notices of the Royal Astronomical Society; v. 434, n. 1, p. 784-795, SEP 2013.
Web of Science Citations: 18

We introduce a new method to study the velocity distribution of galaxy systems, the Hellinger Distance (HD), designed for detecting departures from a Gaussian velocity distribution. Testing different approaches to measure normality of a distribution, we conclude that HD is the least vulnerable method to type I and II statistical errors. We define a relaxed galactic system as the one with unimodal velocity distribution and a normality deviation below a critical value (HD < 0.05). In this work, we study the Gaussian nature of the velocity distribution of the Berlind group sample, and of the FoF groups from the Millennium simulation. For the Berlind group sample (z < 0.1), 67 per cent of the systems are classified as relaxed, while for the Millennium sample we find 63 per cent (z = 0). We verify that in multi-modal groups the average mass of modes in high-multiplicity (N >= 20) systems are significantly larger than in low-multiplicity ones (N < 20), suggesting that groups experience a mass growth at an increasing virialization rate towards z = 0, with larger systems accreting more massive subunits. We also investigate the connection between galaxy properties ({[}Fe/H], Age, eClass, g - r, R-petro and <<mu(petro)>>) and the Gaussianity of the velocity distribution of the groups. Bright galaxies (M-r < -20.7) residing in the inner and outer regions of groups do not show significant differences in the listed quantities regardless if the group has a Gaussian (G) or a Non-Gaussian (NG) velocity distribution. However, the situation is significantly different when we examine the faint galaxies (-20.7 < M-r < -17.9). In G groups, there is a remarkable difference between the galaxy properties of the inner and outer galaxy populations, testifying how the environment is affecting the galaxies. Instead, in NG groups there is no segregation between the properties of galaxies in the inner and outer regions, showing that the properties of these galaxies still reflect the physical processes prevailing in the environment where they were found earlier. (AU)

FAPESP's process: 12/05142-5 - Assembling Baryons to Dark Halos: Stellar Content and the Star Formation History of Early-­type Galaxies
Grantee:Marina Trevisan
Support type: Scholarships in Brazil - Post-Doctorate