APM Surveys for High Redshift Quasars

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.