Bibcode
Park, C.; Song, H.; Einasto, M.; Lietzen, H.; Heinamaki, P.
Referencia bibliográfica
Journal of the Korean Astronomical Society, vol. 48, no. 1, pp. 75-82
Fecha de publicación:
2
2015
Número de citas
23
Número de citas referidas
17
Descripción
We use a volume-limited sample of quasars in the Sloan Digital Sky
Survey (SDSS) DR7 quasar catalog to identify quasar groups and address
their statistical significance. This quasar sample has a uniform
selection function on the sky and nearly a maximum possible contiguous
volume that can be drawn from the DR7 catalog. Quasar groups are
identified by using the Friend-of-Friend algorithm with a set of fixed
comoving linking lengths. We find that the richness distribution of the
richest 100 quasar groups or the size distribution of the largest 100
groups are statistically equivalent with those of randomly-distributed
points with the same number density and sky coverage when groups are
identified with the linking length of 70 h^-1 Mpc. It is shown that the
large-scale structures like the huge Large Quasar Group (U1.27) reported
by Clowes et al. (2013) can be found with high probability even if
quasars have no physical clustering, and does not challenge the
initially homogeneous cosmological models. Our results are statistically
more reliable than those of Nadathur (2013), where the test was made
only for the largest quasar group. It is shown that the linking length
should be smaller than 50 h^-1 Mpc in order for the quasar groups
identified in the DR7 catalog not to be dominated by associations of
quasars grouped by chance. We present 20 richest quasar groups
identified with the linking length of 70 h^-1 Mpc for further analyses.