Active star formation taking place in gas condensations ejected during
the merging of large galaxies is a possible source of dwarf galaxy
formation. This idea, first proposed by
Zwicky (1956), has received
important recent observational support
(Mirabel 1992;
Mirabel et al. 1992;
Elmegreen et al. 1993;
Duc & Mirabel 1994). The
strongest evidence comes from the identification of blue condensations
in the tips of ejected tails of ultraluminous mergers, with typical HI
masses from 
to
.
Objects similar to dwarf irregulars, HII galaxies or Magellanic
irregulars are indeed found in the ejected tails of colliding
galaxies, and some are likely to become detached systems, or isolated
dwarf galaxies (Sanders & Mirabel 1996). A study of
seven Hickson Compact Groups of galaxies
(Hickson 1982; Hunsberger et al. 1996)
exhibiting tidal tails or debris also showed these objects, and
Hunsberger et al. estimate that a third to half of all dwarfs in
compact galaxy groups may have formed during galaxy-galaxy encounters.
Our aim is to look for evidence either in favor or against the possible genesis of dwarf galaxies as a result of strong galactic encounters. To this end we have conducted a search of small, although extended, nebulosities around a sample of luminous infrared galaxies (LIGs) with compact nuclear starbursts. Twelve galaxies were selected from the IRAS bright galaxy sample (Soifer et al. 1989) and from Condon et al. (1991). These galaxies display a wide range in size and luminosity - the observations presented here are not restricted to ultraluminous objects or to well defined merger systems with sharply designed tails. The sample covers a large variety of morphologies and stages in the merging process. It includes, for example, ellipticals with double peaked nuclei, galaxies in groups, and merging spirals that still show their individual spiral structure. Most sample galaxies are included in Arp's (1966) Atlas of Peculiar Galaxies.
For the twelve sample galaxies, this catalogue lists all extended
objects (EOs) found within a field of 
size,
centered at the central galaxy. An account of the observations is
given in Sect. 2. The procedure to identify the EOs in the CCD
frames is described in Sect. 3.
Section 4 presents a description of
the photometric and astrometric calibration.
Section 5 describes the
content of the tables which comprise the main part of the
catalogue. Final remarks are given in Sect. 6.