The statistical nature of the brightest group galaxies
- Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China)
- Department of Astronomy, University of Massachusetts, Amherst, MA 01003-9305 (United States)
- Astronomy Department, Yale University, Box 208101, New Haven, CT 06520-8101 (United States)
- Kavli Institute for Cosmological Physics at the University of Chicago 5640, S. Ellis Avenue, Chicago, IL 60637 (United States)
We examine the statistical properties of the brightest group galaxies (BGGs) by using a complete spectroscopic sample of groups/clusters of galaxies selected from the Data Release 7 of the Sloan Digital Sky Survey. We test whether BGGs and other bright members of groups are consistent with an ordered population among the total population of group galaxies. We find that the luminosity distributions of BGGs do not follow the predictions from the order statistics (OS). The average luminosities of BGGs are systematically brighter than OS predictions. On the other hand, by properly taking into account the brightening effect of the BGGs, the luminosity distributions of the second brightest galaxies are in excellent agreement with the expectations of OS. The brightening of BGGs relative to the OS expectation is consistent with a scenario that the BGGs on average have overgrown about 20% masses relative to the other member galaxies. The growth (ΔM) is not stochastic but correlated with the magnitude gap (G {sub 1,} {sub 2}) between the brightest and the second brightest galaxy. The growth (ΔM) is larger for the groups having more prominent BGGs (larger G {sub 1,} {sub 2}) and averagely contributes about 30% of the final G {sub 1,} {sub 2} of the groups of galaxies.
- OSTI ID:
- 22348057
- Journal Information:
- Astrophysical Journal, Vol. 782, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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