Observations of
Southern Compact Groups of galaxies
Several different types of observations are used to obtain information about a number of key properties of SCGs (see the page on results for a more science-driven compilation of the key topics).
The primary database comprises optical/NIR observations carried out with instruments of ESO and radio observations conducted with the ATCA.
HI line observations
HI line observations conducted with the ATCA are used to achieve several goals:
- trace the distribution of neutral atomic hydrogen gas in the member galaxies of each group studied
- study the kinematics of the HI gas in those galaxies
- search for indications of disturbances in the gas distributions and kinematics that might have been caused by gravitational interactions or other effects (e.g. ram pressure stripping)
- search for intergalactic gas associated with SCGs
- determine the total HI gas mass in each member galaxy and, from that, derive whether group members are HI deficient compared to field galaxies
- confirm group membership established by means of optical spectroscopy (see below)
- determine the groups' velocity dispersion
- determine the group members' rotational velocities and from these total dynamical masses
1.4 GHz radio continuum observations
- determine the distribution of star formation in member galaxies
- estimate the total star formation rates
- distinguish between AGN and starburst activity
- search for and study magnetic fields in member galaxies
Optical imaging
- Study the stellar distribution in member galaxies
- search for signs of disturbances caused by gravitational interactions
Optical spectroscopy
- Determine group membership of galaxies
- derive velocity dispersions for each group
- distinguish between AGN and starburst activity
- determine recession velocities for follow-up HI line observations
Near-infrared imaging
- Study the distribution of the old stellar population
X-ray imaging and spectroscopy
- Study the characteristics of hot thermal gas in member galaxies
- distinguish between AGN and starburst activity
- search for intergalactic hot gas
- estimate the metallicity of interstellar hot ionised gas
From all these we obtain the following results.
