Bibcode
La Barbera, F.; de Carvalho, R. R.; de la Rosa, I. G.; Sorrentino, G.; Gal, R. R.; Kohl-Moreira, J. L.
Referencia bibliográfica
The Astronomical Journal, Volume 137, Issue 4, pp. 3942-3960 (2009).
Fecha de publicación:
4
2009
Número de citas
45
Número de citas referidas
42
Descripción
We use SDSS-DR4 photometric and spectroscopic data out to redshift z ~
0.1 combined with ROSAT All Sky Survey X-ray data to produce a sample of
25 fossil groups (FGs), defined as bound systems dominated by a single,
luminous elliptical galaxy with extended X-ray emission. We examine
possible biases introduced by varying the parameters used to define the
sample, and the main pitfalls are also discussed. The spatial density of
FGs, estimated via the V/V MAX test, is 2.83 ×
10-6 h 3 75 Mpc-3 for
LX > 0.89 × 1042 h -2
75 erg s-1 consistent with Vikhlinin et al., who
examined an X-ray overluminous elliptical galaxy sample (OLEG). We
compare the general properties of FGs identified here with a sample of
bright field ellipticals generated from the same data set. These two
samples show no differences in the distribution of neighboring faint
galaxy density excess, distance from the red sequence in the
color-magnitude diagram, and structural parameters such as a
4 and internal color gradients. Furthermore, examination of
stellar populations shows that our 25 FGs have similar ages,
metallicities, and α-enhancement as the bright field ellipticals,
undermining the idea that these systems represent fossils of a physical
mechanism that occurred at high redshift. Our study reveals no
difference between FGs and field ellipticals, suggesting that FGs might
not be a distinct family of true fossils, but rather the final stage of
mass assembly in the universe.
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