Astron. Astrophys. Suppl. Ser. 134, 75-86

The central region of the Fornax cluster

II. Spectroscopy and radial velocities of member and background galaxies

M. Hilker ^1,2 - L. Infante ² - G. Vieira ² - M. Kissler-Patig ^1,3,4 - T. Richtler ¹

Send offprint request: M. Hilker

1 - Sternwarte der Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
2 - Departamento de Astronomía y Astrofísica, P. Universidad Católica, Casilla 104, Santiago 22, Chile
3 - UCO/Lick Observatory, University of California, Santa Cruz, CA 95064, U.S.A.
4 - Feodor Lynen Fellow of the Alexander von Humboldt Foundation

Received March 23; accepted July 7, 1998

Abstract:

Radial velocities of 94 galaxies brighter than about $V_{\rm tot} = 20$ mag in the direction of the central Fornax cluster have been measured. Except for 8 Fornax members, all galaxies lie in the background. Among the 8 members, there are 5 nucleated dwarf ellipticals that are already listed in the FCC (Ferguson 1989). Two of the 3 "new'' members are very compact and have surface brightnesses comparable to globular clusters, however their luminosities are in the range of dwarf elliptical nuclei.

The measured line indices (especially Mg2, H$\beta$, and iron) of the brighter of the compact objects suggest a solar metallicity, whereas the fainter compact object as well as the dE, Ns have line indices that are similar to those of old metal-poor globular clusters (GCs). However, with these data it is not possible to clearly classify the compact objects either as very bright globular clusters, isolated nuclei of dE, Ns, or even compact ellipticals.

A background galaxy cluster at z = 0.11 has been found just behind the center of the Fornax cluster. This explains the excess population of galaxies reported in Paper I. The brightest galaxy of the background cluster lies only $1\hbox{$.\mkern-4mu^\prime$}1$ south of NGC 1399 and is comparable in absolute luminosity with the central Fornax galaxy itself.

Key words: galaxies: clusters: Fornax cluster -- galaxies: distances and redshifts -- galaxies: abundances -- galaxies: dwarf