Southern sky redshift survey: Clustering of local galaxies

Christopher N.A. Willmer, Luiz Nicolaci Da Costa, Paulo S. Pellegrini

Research output: Contribution to journalArticlepeer-review

123 Scopus citations


We use the two-point correlation function to calculate the clustering properties of the recently completed SSRS2 survey, which probes two well-separated regions of the sky, allowing one to evaluate the sensitivity of sample-to-sample variations. Taking advantage of the large number of galaxies in the combined sample, we also investigate the dependence of clustering on the internal properties of galaxies. The redshift-space correlation function for the combined magnitude-limited sample of the SSRS2 is given by ξ(s) = [s/(5.85 h-1 Mpc)]-1.60 for separations in the range 2 h-1 Mpc ≤ s ≤ 11 h-1 Mpc, while our best estimate for the real-space correlation function is ξ(r) = [r/(5.36 h-1 Mpc)]-1.86. Both are comparable with previous measurements using surveys of optical galaxies over much larger and independent volumes. By comparing the correlation function calculated in redshift and real space, we find that the redshift distortion on intermediate scales is small. This result implies that the observed redshift-space distribution of galaxies is close to that in real space and that β = Ω0.6/b < 1, where Ω is the cosmological density parameter and b is the linear biasing factor for optical galaxies. We have used the SSRS2 sample to study the dependence of ξ on the internal properties of galaxies, such as luminosity, morphology, and color. We confirm earlier results that luminous galaxies (L > L*) are more clustered than sub-L* galaxies and that the luminosity segregation is scale-independent. We also find that early types are more clustered than late types. However, in the absence of rich clusters, the relative bias between early and late types in real space, bE+s0/bs ∼ 1.2, is not as strong as previously estimated. Furthermore, both morphologies present a luminosity-dependent bias, with the early types showing a slightly stronger dependence on luminosity. We also find that red galaxies are significantly more clustered than blue ones, with a mean relative bias of bR/bB ∼ 1.4, stronger than that observed for morphology. Finally, by comparing our results with the measurements obtained from the infrared-selected galaxies, we determine that the relative bias between optical and IRAS galaxies in real space is bo/bI ∼ 1.4.

Original languageEnglish (US)
Pages (from-to)869-884
Number of pages16
JournalAstronomical Journal
Issue number3
StatePublished - Mar 1998
Externally publishedYes


  • Cosmology: observations
  • Galaxies: clusters: general
  • Large-scale structure of universe

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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