SDSS_DR10.GalGroup table

The GalGroup table contains galaxy groups and clusters that are extracted from the Galaxy table using the FoF method.

Table structure

ColumnTypeUCDUnitDescription
groupidintmeta.id
meta.main
group/cluster id
ngalintmeta.numberrichness (number of members) of the group
raj2000doublepos.eq.radegright ascension of the group centre
dej2000doublepos.eq.decdegdeclination of the group centre
zcmbdoublesrc.redshiftCMB-corrected redshift of group, calculated as an average over all group/cluster members
groupdistdoublepos.distanceMpc/hcomoving distance to the group centre
sigma_vfloatstat.stdev
phys.veloc
km/srms radial velocity deviation
sigma_skyfloatstat.stdev
pos.distance
Mpc/hrms deviation of the projected distance in the sky from the group centre; sigma_sky defines the extent of the group in the sky
r_virfloatphys.size.radius
phys.virial
Mpc/hvirial radius (the projected harmonic mean)
r_maxfloatstat.max
phys.size.radius
maximum radius of the group/cluster
mass_nfwfloatphys.mass10+12Msun/hestimated mass of the group assuming the NFW density profile
mass_herfloatphys.mass10+12Msun/hestimated mass of the group assuming the Hernquist density profile
lum_r_groupfloatphys.luminosity10+10Lsun/h2observed luminosity, i.e. the sum of the luminosities of the galaxies in the group/cluster
weightfloatstat.weightweight factor for the group at the mean distance of the group
den1floatsrc.densitynormalised environmental density (mean of group galaxy densities) of the group for the smoothing scale of 1 Mpc/h
den2floatsrc.densitynormalised environmental density (mean of group galaxy densities) of the group for the smoothing scale of 2 Mpc/h
den4floatsrc.densitynormalised environmental density (mean of group galaxy densities) of the group for the smoothing scale of 4 Mpc/h
den8floatsrc.densitynormalised environmental density (mean of group galaxy densities) of the group for the smoothing scale of 8 Mpc/h