GMBCG Cluster Catalog for SDSS DR7

important to know


Do you believe galaxy clusters that do not look like a cluster at all when you look at the image? Here are some images to help you know what a typical cluster looks like.

c c
c c
c c

  Click on the image to see larger one

The following is not a galaxy cluster!


ContacT Info
Jiangang Hao
Center for Particle Astrophysics MS-127
Fermi National Accelerator Laboratory
P.O. Box 500, Batavia, IL 60510
Office Phone:  (630) 840-2705

about this Catalog                           SDSS

The GMBCG cluster catalog for SDSS DR7 covers the legacy survey area of SDSS and spanning a redshift range from 0.1 to 0.55. The catalog consists of over 55,000 rich clusters and is approximately volume limited up to redshift 0.40.

This catalog is an extension of the maxBCG cluster catalog for SDSS (Koester et al 2007) to redshift beyond 0.3 and covers slightly more sky area too (~ 8000 square deg).

maxBCG matches the assumed model cluster filter to select clusters while GMBCG detects clusters by looking at the difference between cluster and background in color space. It is a kind of differential detection compared to maxBCG. Details about the cluster finding algorithm and the catalog can be found from Hao et al 2010.  

Get the Catalog

Click here and Leave your email to receive future updates/imformation of the catalog.

  • Data: The clusters are indexed by BCGs and can be download from here:
Public Catalog Tags: (for the fit format)

      • ObjID: unique id of the BCG. Some of the objids are not long64 type, which are due to a known bug in the sdss dr7 database. We will update the objid after that bug is fixed. For now, matching object using ra/dec is recommended.
      • RA: 0 - 360 degree (J2000)
      • DEC: (J2000)
      • Photoz: photometric redshift
      • Photoz_err: errors of photoz
      • SPZ: spectroscopic redshift of BCG
      • gmr: g-r color
      • gmr_err: measurement errors for g-r
      • rmi:  r-i color
      • rmi_err: measurement errors for r-i
      • model_mag: 5 band (u,g,r,i,z) model magnitude after correction for reddening
      • model_mag_err: 5 band (u,g,r,i,z) model magnitude  errors
      • S_cluster: clustering strength
      • GM_Scaled_Ngals: richness
      • GM_Ngals_weighted: weighted richness
      • WeightOK: if it is set to 1, weighted richness is recommended.
Public Catalog Tags: (for the ASCII format)

  • model_mag in this format is given as: dered_u, dered_g, dered_r, dered_i, dered_z
  • model_mag_err in this format is given as: u_Err, g_Err, r_Err, i_Err, z_Err.

mf    Last updated 11/29/10