Although the existence of a faint background of starlight in the core of the Coma cluster has been well established, its origin is uncertain. This vast sea of stars could have formed outside the galaxies, using gas left over from the time of the cluster’s birth. Alternatively, it might be the accumulated debris generated by interactions between the galaxies over the lifetime of the cluster. Her...

The X-ray galaxy cluster sample from the REFLEX Cluster Survey, which covers the X-ray brightest galaxy clusters detected in the ROSAT All-Sky Survey in the southern sky, is used to construct the X-ray luminosity function of clusters in the local Universe. With 452 clusters detected above an X-ray flux-limit of 3 · 10 erg s cm in 4.24 sr of the sky, this sample is the most comprehensive X-ray c...

Both the X-ray luminosity-temperature (L-T) relationship and the iron abundance distribution of galaxy clusters show intrinsic dispersion. Using a large set of galaxy clusters with measured iron abundances we find a correlation between abundance and the relative deviation of a cluster from the mean L-T relationship. We argue that these observations can be explained by taking into account the ra...

We present the first results of our application of photometric redshifts to the study of galaxy populations in high-redshift clusters. For this survey , we are examining a sample of galaxy clusters at z > 0.6 which have already been well-studied in the optical and infrared wavelengths (Oke, Postman & Lubin 1998). Our main goal is to use photometric redshifts to delineate accurately between fiel...

Two colour photometry of the cluster A1689 reveals a `relative magniication-bias' between lensed blue and red background galaxies, arising from a dependence of the faint galaxy count-slope on colour. The colour distribution is skewed blueward of the far eld, allowing us to measure the cluster magniication and to understand the notorious blueness of large arcs. We show that the magniication info...