“School of Astronomy”
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Paper IPM / Astronomy / 14348 |
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Abstract: | |||||
We study galaxies drawn from the semi-analytic models of Guo et al. (2011) based on the Millennium
Simulation. We establish a set of four observationally measurable parameters which can be used in
combination to identify a subset of galaxy groups which are old, with a very high probability. We therefore
argue that a sample of fossil groups selected based on the luminosity gap will result in a contaminated
sample of old galaxy groups. By adding constraints on the luminosity of the brightest galaxy, and its
offset from the group luminosity centroid, we can considerably improve the age-dating.
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