We create a catalogue of simulated fossil groups and study their properties,
in particular the merging histories of their first-ranked galaxies. We compare
the simulated fossil group properties with those of both simulated non-fossil
and observed fossil groups. Using simulations and a mock galaxy catalogue, we
searched for massive (> 5 × 1013h−1M⊙) fossil
groups in the Millennium Simulation Galaxy Catalogue. In addition, attempted to
identify observed fossil groups in the Sloan Digital Sky Survey Data Release 6
using identical selection criteria. Our predictions on the basis of the
simulation data are:(a) fossil groups comprise about 5.5% of the total
population of groups/clusters with masses larger than 5 x 1013h−1M⊙. This fraction is consistent with the fraction of fossil groups
identified in the SDSS, after all observational biases have been taken into
account; (b) about 88% of the dominant central objects in fossil groups are
elliptical galaxies that have a median R-band absolute magnitude of ∼−23.5−5logh, which is typical of the observed fossil groups known in the
literature; (c)first-ranked galaxies of systems with M> 5 x 1013h−1M⊙, regardless of whether they are either fossil or
non-fossil, are mainly formed by gas-poor mergers; (d) although fossil groups,
in general, assembled most of their virial masses at higher redshifts in
comparison with non-fossil groups, first-ranked galaxies in fossil groups
merged later, i.e. at lower redshifts, compared with their non-fossil-group
counterparts. We therefore expect to observe a number of luminous galaxies in
the centres of fossil groups that show signs of a recent major merger.Comment: 9 pages, 3 figures, accepted for publication in Astronomy &
Astrophysic