S. Phillipps

The surface brightness of IRAS galaxies

Using IRAS measurements, we find positive correlations between both the infrared to optical flux ratio (LFIR/LB) and infrared colour temperature (L60/L100) with optical surface brightness. These correlations can be understood by high surface brightness galaxies having (i) a high star formation rate, or (ii) a high-space density of stars and dust.In an attempt to interpret (ii) above, we have produced radiative transfer models for the dust absorption in a galactic disc. These models indicate that the highest surface brightness galaxies may be the most dust obscured (i.e., optically thick) and that the total luminosity (and, hence, mass) of these galaxies may be considerably underestimated.

Studies of Galaxy Clusters Using APM

The Automatic Plate Measuring System (APM) at the Institute of Astronomy, Cambridge, has been used to obtain surface photometry of a large sample of galaxies. Several studies involving galaxies in the Fornax cluster are currently being undertaken.