2012A&A...543A..64F

We report first results of an investigation of the tidally disturbed galaxy system AM546-324, whose two principal galaxies 2MFGC04711 and AM0546-324 (NED02) were previously classified as interacting doubles. This system was selected to study the interaction of ellipticals in a moderately dense environment. We provide spectral characteristics of the system and present an observational study of the interaction effects on the morphology, kinematics, and stellar population of these galaxies. The study is based on long-slit spectrophotometric data in the range of ∼4500-8000Å obtained with the Gemini Multi-Object Spetrograph at Gemini South (GMOS-S). We have used the stellar population synthesis code STARLIGHT to investigate the star formation history of these galaxies. The Gemini/GMOS-S direct r-G0303 broad band pointing image was used to enhance and study fine morphological structures. The main absorption lines in the spectra were used to determine the radial velocity. Along the whole long-slit signal, the spectra of the Shadowy galaxy (discovered by us), 2MFGC04711, and AM0546-324 (NED02) resemble that of an early-type galaxy. We estimated redshifts of z=0.0696, z=0.0693 and z=0.0718, corresponding to heliocentric velocities of 20141km/s, 20057km/s, and 20754km/s for the Shadowy galaxy, 2MFGC04711 and AM0546-324 (NED02), respectively. The central regions of 2MFGC04711 and AM0546-324 (NED02) are completely dominated by an old stellar population of 2x10⁹<t≤13x10⁹yr and do not show any spatial variation in the contribution of the stellar-population components. The observed rotation profile distribution of 2MFGC04711 and AM0546-324 (NED02) can be adequately interpreted as an ongoing stage of interaction with the Shadowy galaxy as the center of the local gravitational potential-well of the system. The three galaxies are all early-type. The extended and smooth distribution of the material in the Shadowy galaxy is a good laboratory to study direct observational signatures of tidal friction in action.