We present VLT–observations of a recently detected galaxy cluster candidate in the field of the radio–quiet quasar Q 0307−0015. R–band images and multi–object spectra (MOS) have been obtained during the commissioning phase II of FORS1 in December 1998. The presumed central cluster galaxy shows the typical spectrum and surface brightness profile of an early–type galaxy and has a redshift of z=0....

We present CHANDRA observations of the X-ray luminous, distant galaxy cluster RBS797 at z = 0.35. In the central region the X-ray emission shows two pronounced X-ray minima, which are located opposite to each other with respect to the cluster centre. These depressions suggest an interaction between the central radio galaxy and the intra-cluster medium, which would be the first detection in such...

We are looking at quasar environment in the context of large-scale structure (LSS) — a new approach, giving a more informed interpretation of quasar-galaxy correlations. This paper presents our first results for a sample of z ∼ 0.3 quasars. We are using Voronoi tessellation applied in colour (BJ−R) slices for the detection of galaxy clusters and the minimal spanning tree (MST) to delineate the ...

We present ROSAT PSPC and HRI observations of A2111, the richest galaxy cluster photometrically surveyed by Butcher & Oemler (1984). The cluster contains a distinct comet-shaped X-ray subcomponent, which appears hotter than the rest of the cluster. The galaxy and X-ray surface brightness distributions of the cluster show a similarly elongated morphology. These results suggest that the cluster i...

The use of large, X-ray selected galaxy cluster catalogues for cosmological analyses requires a thorough understanding of the X-ray mass estimates.Weak gravitational lensing is an ideal method to shed light on such issues, due to its insensitivity to the cluster dynamical state. We perform a weak lensing calibration of 166 galaxy clusters from the REFLEX and BCS cluster catalogue and compare ou...

We present observations of a remarkable submillimetre-selected galaxy, SMMJ16359+6612. This distant galaxy lies behind the core of a massive cluster of galaxies, A 2218, and is gravitationally lensed by the foreground cluster into three discrete images which were identified in deep submillimetre maps of the cluster core at both 450 and 850μm. Subsequent follow-up using deep optical and near-inf...

We report the first detailed X-ray and optical observations of the medium-distant cluster A33 obtained with the Beppo-SAX satellite and with the UH 2.2m and Keck II telescopes at Mauna Kea. The information deduced from X-ray and optical imaging and spectroscopic data allowed us to identify the X-ray source 1SAXJ0027.21930 as the X-ray counterpart of the A33 cluster. The faint, F2−10 keV ≈ 2.4×1...

A study of the globular cluster systems of 23 brightest, or central, galaxies in 19 Abell clusters has recently been completed (Blakeslee 1997). This letter presents some of the newly discovered correlations of the globular cluster specific frequency SN in these galaxies with other galaxy and cluster properties and puts forth an interpretation of these results. SN is found to correlate strongly...

A striking signal of dark matter beyond the standard model is the existence of cores in the centre of galaxy clusters. Recent simulations predict that a Brightest Cluster Galaxy (BCG) inside a cored galaxy cluster will exhibit residual wobbling due to previous major mergers, long after the relaxation of the overall cluster. This phenomenon is absent with standard cold dark matter where a cuspy ...