Dwarfs after mergers? The case of NGC 520, NGC 772, Arp 141, NGC 3226/7, NGC 3656 and Arp 299

¹ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK e-mail: edelgado@ast.cam.ac.uk
² Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain e-mail: cmt@ll.iac.es, hdeeg@ll.iac.es
³ Laboratoire d'Astrophysique de Marseille, Traverse du Siphon - Les Trois Lucs, 13376 Marseille, France e-mail: jorge.iglesias@astrsp-mrs.fr

Corresponding author: E. J. Delgado-Donate, edelgado@ast.cam.ac.uk

Received: 21 June 2002
Accepted: 13 February 2003

Abstract

We present results from a survey of dwarf galaxy candidates in the vicinity of strongly interacting galaxies. The goal of the survey was a test of the hypothesis that massive condensations of stars and Hi in tidal tails of large interacting galaxies may be a significant source of independent, self-gravitating dwarf galaxies. These so called tidal dwarf galaxies (TDG) can be expected to resemble the blue luminous knots found in tidal tails, but also might appear as redder, evolved systems if formed much before they are being observed. For the present study, a homogeneous subsample of 6 fields was selected from the catalog of extended objects in fields around 15 strongly interacting galaxies by Deeg et al. (1998). Criteria for the subsample were: similar redshifts of the central interacting galaxies, and photometric completeness of the extended objects in V and R. The number density of these TDG candidates was compared with expected background galaxy densities. Within the statistical errors, background galaxies account for most, if not all of the extended objects. There is no evidence for a substantial locally formed dwarf galaxy population. Thus, we conclude that field galaxy-galaxy interactions are likely to result in the formation of only a few long-lived TDG.