Optical Identification of the ASCA Lynx Deep Survey: An Association of Quasi-Stellar Objects and a Supercluster at z=1.3?

Results of optical identification of the ASCA Lynx Deep Survey are presented. Six X-ray sources are detected in the 2-7 keV band using the Solid-State Imaging Spectrometer in a ~20^'×20^' field of view with fluxes larger than ~4×10^-14 ergs s^-1 cm^-2 in the band. Follow-up optical spectroscopic observations were made, and five out of six sources are identified with active galactic nuclei/quasi-stellar objects (AGNs/QSOs) at redshifts of 0.5-1.3. We also identify two more additional X-ray sources detected in a soft X-ray band with AGNs/QSOs. We find that three QSOs identified are located at z~1.3. Two rich clusters and several groups of galaxies are also placed at the same redshift in the surveyed field, and projected separations between the QSOs and the clusters are 3-8 Mpc at the redshift.

Based on observations made with the Kiso Observatory, which is operated by Institute of Astronomy, the University of Tokyo, with the Kitt Peak National Observatory 2.1 and 4 m telescopes, which are operated by the National Optical Astronomy Observatories (NOAO), operated by AURA, Inc., under contract with the National Science Foundation, with the University of Hawaii 88 Inch telescope, and with the William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias.