SCG0018-4854: a young and dynamic compact group^*

I. Kinematical analyses

¹ Universitá degli Studi dell'Insubria, via Valleggio 11, 22100 Como, Italy e-mail: valentina.presotto@brera.inaf.it
² INAF - Osservatorio Astronomico di Brera via Brera 28, 20122 Milan, Italy
³ European Southern Observatory (ESO) Alonso de Cordova 3107, Santiago, Chile
⁴ Institut für Astro- und Teilchenphysik, Universität Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria

Received: 13 July 2009
Accepted: 20 September 2009

Abstract

Aims. It has been widely recognized that processes taking place inside group environment could be important drivers of galaxy evolution. Compact groups of galaxies in particular are excellent laboratories for studying galaxy interactions and their effects on the evolution of galaxies due to their high density and low velocity dispersion. SCG0018-4854 is a remarkably high galaxy density and low velocity dispersion group with evidence of a recent interaction. It has been detected and analyzed at different wavelengths, but its kinematics have never been studied in detail.

Methods. We obtained VLT FORS2 optical observations and present spectroscopic and photometric evidence to illustrate how dramatically galaxy interactions have affected each of the four group member galaxies.

Results. For each galaxy, we detected peculiar kinematics and evidence of recent star formation. In particular, the gas and stellar radial velocity curves of two galaxies are irregular with a level of asymmetry similar to that of other interacting galaxies. We discovered a bar inside NGC 92 thereby revising a previous morphological classification, and we obtained spectroscopic confirmation of the galactic-scale outflow within NGC 89.

Conclusions. The peculiar kinematics and dynamical considerations provide a rough estimate of the age of the latest interaction of τ ≈ 0.2-0.7 Gyr, suggesting that SCG0018-4854 is a young and dynamical group.