Showing papers by "Mike Irwin published in 1992"

APM Surveys for High Redshift Quasars

Abstract: Two related surveys for high redshift quasars are described: (i) The APM BRI survey for z > 4 quasars. This survey currently covers ∼2000 deg2 to a nominal limiting magnitude of R = 19 and has resulted in eighteen new spectroscopically confirmed quasars with z > 4. No decline in the space density of luminous quasars is observed over the redshift range z = 2 to z = 4.5. (ii) The APM has been used to identify radio sources from the MIT-Greenbank (MG) 5Ghz radio survey on the POSS-I O and E plates. A subset have been selected for follow-up on the basis of their extreme red colours. Four new radio loud quasars with z > 3.5 have been discovered including one with z = 3.9.

Double star CCD astrometry and photometry

Abstract: Results are presented for angular separation, position angle and V and R photometry for 2373 binary stars, obtained with the CCD camera on the 1-m Jacobus Kapteyn Telescope at La Palma. The stars are part of the Input Catalogue of the Hipparcos Astrometric Satellite launched in 1989 August, and the purpose of our measurements is to assist in the satellite reductions.

A search for QSOs behind globular clusters

Abstract: In order to provide a reference frame against which proper motions of stars in globular clusters might be measured, we have searched for QSOs projected behind (primarily) northern globular clusters. Optical, x-ray, and radio techniques were used to select QSO candidates in these relatively crowded fields. Optical photometry, obtained from both CCD images and UK Schmidt Telescope photographic plates, resulted in most of the QSO identifications. Follow-up spectroscopy on the Multiple Mirror Telescope has confirmed fourteen new QSOs and one H II galaxy in the fields of eight clusters