Optical and radio survey of
Southern Compact Groups of galaxies

Investigators:

E. Pompei (European Southern Observatory, Santiago, Chile)
M. Dahlem (CSIRO/ATNF, Narrabri, Australia)
A. Iovino (INAF-Osservatorio astronomico di Brera, Milano, Italy)

Overview

Compact groups of galaxies are considered first-class laboratories for studies of the influence of galaxy interactions on their evolution due to the relatively high density of their member galaxies galaxies and their short crossing times. In addition to this, galaxies in compact groups and loose groups represent about 50%-70% of the galaxy population in the local Universe and are thought to be the link between field and cluster galaxies, playing an important role in the formation and evolution of large scale structures.

Southern Compact Groups of galaxies were defined by Prandoni et al. (1994) [see also Iovino et al. (1999) and Iovino (2002)] using new, automated selection criteria that avoid the usual biases introduced by earlier selection criteria of candidate groups.

In broad terms the survey of Southern Compact Groups (SCGs) of galaxies conducted by us aims at a systematic study of the effects of galaxy interactions on their evolution and of the difference between galaxies in such dense environments compared to field galaxies.

The observational techniques employed in this study are as follows:

• HI line observations
• 1.4 GHz radio continuum observations
• Optical imaging
• Optical spectroscopy
• Near-infrared imaging
• X-ray imaging and spectroscopy

From these the following results are derived:

• Group membership
• HI gas properties
• Signs of gravitational disturbances
• Starburst vs. AGN activity
• Level and distribution of star formation activity
• Stellar population studies
• Group dynamics

These can be compared with the properties of field galaxies to determine the differences between isolated galaxies and galaxies in dense environments, which provides us with a measure of the influence of galaxy interactions on their (chemical and dynamical) evolution.

Here a list of relevant publications. A poster presented by us at a recent summer school can be used as an example of early results.

These pages will be updated and complemented as new information becomes available.