We propose that HCG 54 is a system that consists of at least two late type galaxies plus a dwarf companion involved in recent tidal interactions and a merger. Two low mass disk systems merged and induced the formation of a central blue, bar-like structure embedded in a red, round stellar envelope, outside which lies several stellar shells. A luminous starburst is associated with HCG 54b while HCG 54c and d are the remnant debris of the recent merger undergoing modest star formation activity. This merger is probably in a very advanced state. The 20 kpc long gaseous tidal tail discovered in HI may be a result of the same merger or driven by the dwarf galaxy A1127+2054 found at a projected distance of 8 kpc from the tip. In either scenario, it is likely playing a role in shaping the appearance of this tidal tail. Unfortunately current theoretical or numerical models do not provide information on the kinematics or the distribution of induced star formation in low mass disk mergers. Few similar systems have been discussed in the literature, and the present data should provide valuable inputs for future modeling of mergers involving low mass galaxies.
Acknowledgements
We wish to thank Dr. Masegosa and Dr. Márquez for the help with the R observations at the NOT and their valuable comments. LV-M, AO and JP are partially supported by DGI (Spain) Grant AYA2000-1564 and Junta de Andalucía (Spain). JMV is partially supported by DGI (Spain) Grant AYA2001-3939-C03-01 and Junta de Andalucía (Spain).
Copyright ESO 2002