A study of the remarkable galaxy system AM 546-324 (the core of Abell S0546)^⋆

¹ MCTI/Laboratório Nacional de Astrofísica, Rua Estados Unidos 154, Bairro das Nações, CEP 37.504-364, Itajubá, MG, Brazil
e-mail: mfaundez@lna.br; mabans@lna.br
² Universidade do Vale do Paraíba – UNIVAP, Av. Shishima Hifumi 2911, Urbanova CEP 12244-000, São José dos Campos, SP, Brazil
e-mail: angela.krabbe@gmail.com; irapuan@univap.br
³ UNIFEI, Instituto de Engenharia de Produção e Gestão, Av. BPS 1303 Pinheirinho, 37500-903 Itajubá, MG, Brazil
⁴ UEFS, Departamento de Física, Av. Transnordestina S/N, Novo Horizonte, CEP 44036-900, Feira de Santana, BA, Brazil
⁵ UEFS, Observatório Astronômico Antares, Rua da Barra 925, Jardim Cruzeiro, CEP 44015-430, Feira de Santana, BA, Brazil
e-mail: paulopoppe@gmail.com; vmartin1963@gmail.com; irafbear@gmail.com;

Received: 17 February 2012
Accepted: 7 May 2012

Abstract

Aims. We report first results of an investigation of the tidally disturbed galaxy system AM 546-324, whose two principal galaxies 2MFGC 04711 and AM 0546-324 (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.

Methods. The study is based on long-slit spectrophotometric data in the range of  ~4500−8000 Å 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.

Results. Along the whole long-slit signal, the spectra of the Shadowy galaxy (discovered by us), 2MFGC 04711, and AM 0546-324 (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 20 141 km s^-1, 20 057 km s^-1, and 20 754 km s^-1 for the Shadowy galaxy, 2MFGC 04711 and AM 0546-324 (NED02), respectively. The central regions of 2MFGC 04711 and AM 0546-324 (NED02) are completely dominated by an old stellar population of 2 × 10⁹ < t ≤ 13 × 10⁹ yr and do not show any spatial variation in the contribution of the stellar-population components.

Conclusions. The observed rotation profile distribution of 2MFGC 04711 and AM 0546-324 (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.