Groups and Clusters
SDSS DR7

SDSS DR7 Catalogues

Here you can download the corresponding group and cluster catalogues for SDSS DR7.

Sample Galaxy Catalogue Group Catalogue Mock Catalogues
Mr19 Galaxy Catalogue Group Catalogue Mock Catalogues
Mr20 Galaxy Catalogue Group Catalogue Mock Catalogues
Mr21 Galaxy Catalogue Group Catalogue Mock Catalogues

Volume-limited Samples - SDSS DR7

We start with the NYU Value-Added Galaxy Catalog (NYU-VAGC; version: sample14). All galaxy luminosities are K-corrected and passive evolution-corrected to redshift 0.1 (see Blanton et al. 2003). Galaxies that don't have measured redshifts are included in the sample and placed at the redshift of their nearest neighbor on the sky. We then construct three volume-limited sub-samples of galaxies with the following characteristics:

Name < Mr zmin zmax Ng ng
(h/Mpc)3
Mr19 -19 0.02 0.067 90893 0.01503
Mr20 -20 0.02 0.106 144943 0.00593
Mr21 -21 0.02 0.165 96400 0.00104

where Mr is the resulting limiting r-band absolute magnitude; zmin and zmax are the redshift limits of each sample; Ng, the number of galaxies; and ng, the number density in (h/Mpc)3.

Group and cluster Catalogues

For each volume-limited sample, we present a catalog of groups and a catalog of group members.
These catalogs can be downloaded as ASCII tables containing the following columns:

  • Group Catalog - DR7

    Name Description Units Column Number
    Group ID An integer ID for each group. Group ID 1
    N Total number of galaxies in the group. - 2
    RA Right ascension of the group centroid. Degrees 3
    Dec Declination of the group centroid. Degrees 4
    cz Velocity of the group centroid km/s 5
    σv Velocity dispersion of the galaxies in the group. km/s 6
    Mg Total absolute g-band magnitude of all galaxies in the group. Magnitudes 7
    Mr Total absolute r-band magnitude of all galaxies in the group. Magnitudes. 8
    redge Projected root-mean-square radius of group. Mpc/h 9
    log M*,G Total stellar mass in the group. Msun 10
    log sSFRtot,G Total specific star formation rate of the group Msun yr-1 11

  • Galaxy Catalog - DR7

    Name Description Units Column Number
    Gal. ID An integer ID for each galaxy corresponding to the NYU-VAGC catalogue. Group ID 1
    RA Right ascension of the galaxy. Degrees 2
    Dec Declination of the galaxy. Degrees 3
    cz Velocity of the galaxy. km/s 4
    M0.1,g Absolute g-band magnitude the galaxy.
    Corrected to a redshift of z = 0.1.    		 Magnitudes 5
    M0.1,r Absolute r-band magnitude the galaxy.
    Corrected to a redshift of z = 0.1.    		 Magnitudes 6
    Sersic Sersic index of the galaxy. - 7
    fibcol Fiber collision flag.
    0 if galaxy has a measured redshift, 1 if it got the redshift of its nearest neighbor.    		 - 8
    redge Distance of the galaxy from the survey edge. Mpc/h 9
    log M* Stellar mass in the galaxy. Msun 10
    Flag M* Galaxy stellar mass flag.
    1 if galaxy obtained its stellar mass from the JHU-MPA VAGC.
    0 if galaxy obtained its stellar mass from Bell2003.     		- 11
    log sSFR Specific star formation rate of the galaxy.
    -999 if galaxy didn't have a match in the JHU-MPA VAGC.     		Msun yr-1 12
    Group ID The ID of the group to which the galaxy belongs. - 13
    Type Type of galaxy within the group.
    1 if galaxy is a group central. 0 if galaxy is a group satellite.     		- 14