The identification of two z3.8 QSOs
in a deep CCD survey

Introduction

Although now overtaken as the most distant objects known (Dey et al. 1998; Hu, Cowie & McMahon 1998), QSOs remain the brightest optical sources found in the distant Universe and they can therefore be used to study the structure and characteristics of gas along their sight-lines (e.g. Liske & Webb 1998). While QSOs are relatively numerous at , their numbers drop significantly at higher redshifts, -4 (Shaver et al. 1998). At the time of writing there are roughly z>3.7 QSOs catalogued in NED, selected using a variety of techniques. Of these, around have been detected as X-ray sources and -20 are identified as radio sources.

In this communication we present the identification of two QSOs, found during a deep CCD survey of moderate redshift clusters. The two QSOs lie in the fields of A1758 (z=0.280) and A2261 (z=0.225) and they were identified as candidate high-redshift sources from their stellar morphologies, relatively blue optical colours and very red UV-optical colours. Their redshifts have been subsequently confirmed from spectroscopic observations. In the next section we present the observations of these two objects before going on to discuss their observed properties. Throughout we assume and kmsMpc.

© Copyright Astronomical Society of Australia 1997