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J/A+A/514/A102      SDSS DR7 groups of galaxies              (Tago+, 2010)

Groups of galaxies in the SDSS Data Release 7. Flux- and volume-limited samples. Tago E., Saar E., Tempel E., Einasto J., Einasto M., Nurmi P., Heinamaki P. <Astron. Astrophys. 514, A102 (2010)> =2010A&A...514A.102T
ADC_Keywords: Galaxy catalogs ; Clusters, galaxy ; Galaxies, photometry Keywords: cosmology: observations - large-scale structure of the Universe - galaxies: clusters: general - catalogues Abstract: We extract groups of galaxies as flux-limited and volume-limited samples from the SDSS Data Release 7 to study the supercluster-void network and environmental properties of groups therein. Volume-limited catalogues are particularly useful for comparison of numerical simulations of dark matter halos and the large-scale structure with observations. Extraction of a volume-limited sample of galaxies and groups requires special care to avoid excluding too much observational data. We use a modified friends-of-friends (FoF) method with a slightly variable linking length to obtain a preliminary flux-limited sample. We use the flux-limited groups as the basic sample to include as many galaxies as possible in the volume-limited samples. To determine the scaling of the linking length we calibrated group sizes and mean galaxy number densities within groups by magnitude dilution of a nearby group sub-sample to follow the properties of groups with higher luminosity limits. Our final flux-limited sample contains 78800 groups, and volume-limited subsamples with absolute magnitude limits Mr=-18, -19, -20, and -21 contain 5463, 12590, 18973, and 9139 groups, respectively, in the DR7 main galaxy main area survey. The spatial number densities of our groups within the subsamples, as well as the mean sizes and rms velocities of our groups practically do not change from sub-sample to sub-sample. This means that the catalogues are homogeneous and well suited for comparison with simulations. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2a.dat 104 78800 DR7 flux-limited groups table2b.dat 104 5463 DR7 flux-limited Mr < -18 groups table2c.dat 104 12590 DR7 flux-limited Mr < -19 groups table2d.dat 104 18973 DR7 flux-limited Mr < -20 groups table2e.dat 104 9139 DR7 flux-limited Mr < -21 groups table2f.dat 118 583362 DR7 flux-limited galaxies table2g.dat 118 40665 DR7 volume-limited Mr < -18 galaxies table2h.dat 118 94912 DR7 volume-limited Mr < -19 galaxies table2i.dat 118 148195 DR7 volume-limited Mr < -20 galaxies table2j.dat 118 103978 DR7 volume-limited Mr < -21 galaxies
See also: J/A+AS/123/119 : The supercluster-void network. I. (Einasto+ 1997) J/A+A/336/35 : Shape and orientation of superclusters (Jaaniste+, 1998) J/AJ/122/2222 : Superclusters of Abell and X-ray clusters (Einasto+, 2001) J/AJ/123/51 : Distribution of Abell and APM clusters (Einasto+, 2002) J/A+A/459/L1 : Supercluster sample from SDSS DR4 (Einasto+, 2006) J/AN/327/365 : Clusters and groups of galaxies in 2dF (Tago+, 2006) J/A+A/479/927 : Group of galaxies in SDSS 5 (Tago+, 2008) J/A+A/462/811 : Superclusters of galaxies from 2dF (Einasto+, 2007) Byte-by-byte Description of file: table2[abcde].dat
Bytes Format Units Label Explanations
1- 6 I6 --- Group Group identification number 8- 12 I5 --- Ngal Richness (number of member galaxies) 14- 25 F12.8 deg RAdeg Right Ascension (mean of member galaxies), J2000 27- 38 F12.8 deg DEdeg Declination (mean of member galaxies), J2000 40- 47 F8.4 Mpc Dist Comoving distance (mean of member galaxies) (G1) 49- 55 F7.4 Mpc Size Maximum projected linear size (G1) 57- 65 F9.6 Mpc dispD rms deviation of projected distance (G1) 67- 75 F9.4 km/s dispV rms radial velocity 77- 85 F9.6 Mpc Rvir Virial radius (projected harmonic mean) (G1) 87- 92 F6.3 --- w Luminosity weight 95-104 F10.6 10+10Lsun Lobs Observed total group luminosity (G1)
Byte-by-byte Description of file: table2[fghij].dat
Bytes Format Units Label Explanations
2- 7 I6 --- Group Group ID number 10- 14 I5 --- Ngal Group richness 16- 27 F12.8 deg RAdeg Right Ascension (J2000.0) 29- 40 F12.8 deg DEdeg Declination (J2000.0) 42- 49 F8.4 Mpc Dist Co-moving distance corrected for CMB (G1) 51- 59 F9.5 mag uMAG Absolute u magnitude 61- 69 F9.5 mag gMAG Absolute g magnitude 71- 79 F9.5 mag rMAG Absolute r magnitude 81- 89 F9.5 mag iMAG Absolute i magnitude 91- 99 F9.5 mag zMAG Absolute z magnitude 101-106 F6.4 --- w Luminosity weight 110-118 F9.6 10+10Lsun Lr Luminosity in r band (10^10^/h^2^)(G1)
Global notes: Note (G1): cosmology with h=H0/100, Ωm=0.27, ΩΛ=0.73. * Distances are in Mpc/h * Luminosities are in 10+10L/h2
Acknowledgements: Erik Tago, erik(at)
(End) Erik Tago [Tartu Obs., Estonia], Patricia Vannier [CDS] 10-Mar-2010
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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