EDP Sciences
Free access
Volume 403, Number 1, May III 2003
Page(s) 73 - 81
Section Galactic structure and dynamics
DOI http://dx.doi.org/10.1051/0004-6361:20030254

A&A 403, 73-81 (2003)
DOI: 10.1051/0004-6361:20030254

The multiplicity function of galaxies

E. Puddu1, E. De Filippis1, 2, G. Longo3, 1, S. Andreon1, 4 and R. R. Gal5

1  INAF - Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy
2  Astrophysics Research Institute, Liverpool John Moores University, Egerton Wharf, Twelve Quays House, Birkenhead CH41 1LD, UK
3  Università di Napoli Federico II, via Cinthia, 80126 Napoli, Italy
4  INAF - Osservatorio Astronomico di Brera, via Brera 28, 20121 Milano, Italy
5  Department of Physics and Astronomy, Johns Hopkins University, Baltimore - MD, USA

(Received 21 November 2002 / Accepted 4 February 2003 )

The multiplicity function (MF) of groups and clusters of galaxies is determined using galaxy catalogues extracted from a set of Digitized Palomar Sky Survey (DPOSS) plates. The two different types of structures (of low and high richness) were identified using two different algorithms: a modified version of the van Albada method for groups, and a peak finding algorithm for larger structures. In a 300 deg 2 area up to z<0.2, we find 2944 groups and 179 clusters. Our MF covers a wide range of richnesses, from 2 to 200, and the two MFs derived by the two algorithms match smoothly without the need for additional conditions or normalisations. The resulting multiplicity function, of slope $\alpha= -2.08 \pm 0.07$, strongly resembles a power law.

Key words: galaxies: clusters: general -- galaxies: general

Offprint request: E. Puddu, puddu@na.astro.it

© ESO 2003