Program: GN-2011B-Q-15

Analysis of the spectra of SDSS quasars in the redshift interval 5.7<z<6.5, has shown that z=6 marks the threshold of the epoch of cosmic reionisation. Because Ly-alpha moves out of the z band at z=6.5, a wide-field near-infrared survey is required to find quasars at z>6.5, in order to explore the epoch of reionisation. The UKIDSS LAS is the largest survey suitable for this work, and we are searching it for quasars 5.7<z<7.2. Last semester we discovered a quasar of redshift z=7.085. The transmission spectrum shows the characteristic profile of a damping wing, indicating that along this line of sight the intergalactic medium at z=7 was substantially neutral: this is a breakthrough in the study of cosmic reionisation. We have now completed analysis of 2200 sq degs of the total 3792 sq degs of the LAS. We have in addition discovered 7 new quasars 5.7<z<6.3, and rediscovered the 6 SDSS quasars in these fields. Reionisation is predicted to be a patchy process so it is important to increase the sample of quasars, especially at z>6.5. Here we apply to expand the survey to 2700 sq degs. Our selection methods now result in a 100% success rate at the spectroscopic stage.