Groups and Clusters
SDSS DR3

SDSS DR3 Catalogues

Here you can download the corresponding group and cluster catalogues for SDSS DR3.

Sample Galaxy Catalogue Group Catalogue Mock Catalogues Multiplicity Function
Mr18 Galaxy Catalogue Group Catalogue Mock Catalogues Multiplicity Functions
Mr19 Galaxy Catalogue Group Catalogue Mock Catalogues Multiplicity Functions
Mr20 Galaxy Catalogue Group Catalogue Mock Catalogues Multiplicity Functions

Volume-limited Samples - SDSS DR3

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
Mr18 -18 0.015 0.045 18895 0.02434
Mr19 -19 0.015 0.068 37820 0.01396
Mr20 -20 0.015 0.1 57138 0.00673

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 - DR3

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 - DR3

    Name Description Units Column Number
    Group ID An integer ID for each group. Group ID 1
    RA Right ascension of the group centroid. Degrees 2
    Dec Declination of the group centroid. Degrees 3
    cz Velocity of the group centroid km/s 4
    N Total number of galaxies in the group. - 5
    Mr Total absolute r-band magnitude of all galaxies in the group. Magnitudes 6
    (g-r)tot Total g-r color of all galaxies in the group Magnitudes 7
    σv Velocity dispersion of the galaxies in the group. km/s 8
    Rperp,rms Projected root-mean-square radius of group. Mpc/h 9
    redge Distance of group from survey edge Mpc/h 10

  • Galaxy Catalog - DR3

    Name Description Units Column Number
    Group ID The ID of the group to which the galaxy belongs. - 1
    RA Right ascension of the galaxy. Degrees 2
    Dec Declination of the galaxy. Degrees 3
    z Redshift of the galaxy. - 4
    M0.1,g Absolute g-band magnitude the galaxy.
    Corrected to a redshift of z = 0.1.    		 Magnitudes 5
    Mr Absolute r-band magnitude the galaxy. Magnitudes 6
    (g-r) (g-r) color 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

Multiplicity Functions - SDSS DR3

We measure the multiplicity function (the space density of groups as a function of group multiplicity - or richness) for each group catalog after correcting for fiber collisions and survey edge effects. The multiplicity fuctions are shown in the figure to the right. These multiplicity functions can be downloaded as ASCII tables containing the following columns:

Name Description Units Column Number
Nmin Minimum group richness in bin. - 1
Nmax Maximum group richness in bin. - 2
ngrp (N) Space density of groups with richness within the bin, divided by the bin width dN. (h/Mpc)3 3
σn,grp Error in ngrp estimated from the dispersion among independent mock catalogs. (h/Mpc)3 4
σn,grp (Poisson) Poisson error in ngrp estimated from the number of groups in each bin. (h/Mpc)3 5

The corresponding files can be downloaded in the SDSS DR3 section.