ar X iv : a st ro - p h / 06 11 22 8 v 1 7 N ov 2 00 6 How large is the population of heavily obscured X - ray sources ?

ar X iv : a st ro - p h / 01 11 13 6 v 1 7 N ov 2 00 1 1 Active Optics in Modern , Large Optical Telescopes

ar X iv : a st ro - p h / 06 11 54 4 v 1 1 6 N ov 2 00 6 Discovery of a nearby twin of SN 1987 A ’ s nebula around the

ar X iv : a st ro - p h / 06 11 09 9 v 1 2 N ov 2 00 6 Nuclear Activity in UZC Compact Groups of Galaxies

ar X iv : a st ro - p h / 06 11 43 8 v 1 1 4 N ov 2 00 6 Lack of cooling flow clusters at z > 0 . 5

The goal of this work is to study the incidence rate of “cooling flows” in the high redshift clusters using Chandra observations of z > 0.5 objects from a new large, X-ray selected catalog [1]. We find that only a very small fraction of high-z objects have cuspy X-ray brightness profiles, which is a characteristic feature of the cooling flow clusters at z ∼ 0. The observed lack of cooling flows...

ar X iv : a st ro - p h / 05 11 74 7 v 1 2 6 N ov 2 00 5 1 THE NATURE OF X - RAY ABSORBED STARBURST QSOS AND THE QSO EVOLUTIONARY SCHEME

In contradiction to the simple AGN unification schemes, there exists a significant population of broad line, z ∼ 2 QSOs which have heavily absorbed X-ray spectra. These objects have luminosities and redshifts characteristic of the sources that produce the bulk of the QSO luminosity in the universe. Our follow up observations in the submil-limetre show that these QSOs are embedded in ultralumi-n...