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Astron. Astrophys. 353, 57-62 (2000)

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The redshift-space two-point correlation function of galaxy groups in the CfA2 and SSRS2 surveys

Marisa Girardi 1, Walter Boschin 2 and Luiz N. da Costa 3,4

1 Dipartimento di Astronomia, Università degli Studi di Trieste, Via Tiepolo 11, 34100 Trieste, Italy (girardi@ts.astro.it)
2 Osservatorio Astronomico di Trieste, Via Tiepolo 11, 34100 Trieste, Italy (boschin@ts.astro.it)
3 European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany (ldacosta@eso.org)
4 Departamento de Astronomia CNPq/Observatorio Nacional, Rua General Jose Cristino, 77, Rio de Janeiro, Brazil 20.921

Received 9 August 1999 / Accepted 5 November 1999


We measure the two-point redshift-space correlation function of loose groups of galaxies, [FORMULA], for the combined CfA2 and SSRS2 surveys. Our combined group catalog constitutes the largest homogeneous sample available (885 groups). We compare [FORMULA] with the correlation function of galaxies, [FORMULA], in the same volume. We find that groups are significantly more clustered than galaxies: [FORMULA] =[FORMULA]. A similar result holds when we analyze a volume-limited sample (distance limit 78 h-1 Mpc) of 139 groups. For these groups, with median velocity dispersion [FORMULA] km s-1 and mean group separation [FORMULA] h-1 Mpc, we find that the correlation length is [FORMULA] h-1 Mpc, which is significantly smaller than that found for rich clusters. We conclude that clustering properties of loose groups of galaxies are intermediate between galaxies and rich clusters. Moreover, we find evidence that group clustering depends on physical properties of groups: correlation strengthens for increasing [FORMULA].

Key words: cosmology: large-scale structure of Universe – galaxies: clusters: general – galaxies: statistics

Send offprint requests to: M. Girardi (girardi@ts.astro.it)

© European Southern Observatory (ESO) 2000

Online publication: December 8, 1999