EDP Sciences
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Volume 397, Number 1, January I 2003
Page(s) 63 - 70
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20021498

A&A 397, 63-70 (2003)
DOI: 10.1051/0004-6361:20021498

The mass function of the Las Campanas loose groups of galaxies

P. Heinämäki1, 2, J. Einasto1, M. Einasto1, E. Saar1, D. L. Tucker3 and V. Müller4

1  Tartu Observatory, 61602 Tõravere, Estonia
2  Tuorla Observatory, Väisäläntie 20, 21500 Piikkiö, Finland
3  Fermi National Acceleration Laboratory, M8 127, PO Box 500, Batavia, IL 60510, USA
4  Astrophysical Institute Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany

(Received 18 February 2002 / Accepted 10 October 2002 )

We have determined the mass function of loose groups of galaxies in the Las Campanas Redshift Survey. Loose groups of galaxies in the LCRS range in mass from $M \sim 10^{12}~M_{\odot}$ to $10^{15}~{M}_{\odot}$. We find that the sample is almost complete for masses in the interval $5\times 10^{13}{-}8\times
10^{14}~{M}_{\odot}$ . Comparison of the observed mass function with theoretical mass functions obtained from N-body simulations shows good agreement with a CDM model with the parameters $\Omega_{\rm m} =
0.3$ , $\Omega_{\Lambda} = 0.7$ and the amplitude of perturbations about $\sigma_8=0.78{-}0.87$. For smaller masses the mass function of LCRS loose groups flattens out, differing considerably from the group mass function found by Girardi & Giuricin (2000) and from mass functions obtained by numerical simulations.

Key words: cosmology: observations -- cosmology: large-scale structure of Universe

Offprint request: P. Heinämäki, pekka@aai.ee

© ESO 2003