An Optical Catalog of the Chandra Large Area Synoptic X-ray Survey Sources

We present photometric and spectroscopic observations of the X-ray sources detected in the wide-area, moderately deep Chandra Large Area Synoptic X-ray Survey of the Lockman Hole-Northwest field. We have B, V , R, I, and z photometry for 521 (99%) of the 525 sources in the X-ray catalog and spectroscopic redshifts for 271 (52%), including 20 stars. We do not find evidence for redshift groupings of the X-ray sources, like those found in the Chandra Deep Field surveys, because of the larger solid angle covered by this survey. We separate the X-ray sources by optical spectral type and examine the colors, apparent and absolute magnitudes, and redshift distributions for the broad-line and non-broad-line active galactic nuclei. Combining our wide-area survey with other Chandra and XMM-Newton hard X-ray surveys, we find a definite lack of luminous, high accretion rate sources at z < 1, consistent with previous observations that showed that supermassive black hole growth is dominated at low redshifts by sources with low accretion rates. Subject headings: X-ray:galaxies — general Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The observatory was made possible by the generous financial support of the W. M. Keck Foundation. Based in part on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. Based in part on data collected at Subaru Telescope and obtained from the SMOKA science archive at Astronomical Data Analysis Center, which are operated by the National Astronomical Observatory of Japan. Based in part on data collected at the WIYN Observatory, which is a joint facility of the University of Wisconsin, Indiana University, Yale University, and the National Optical Astronomy Observatory. Department of Astronomy, University of Wisconsin at Madison, 475 North Charter Street, Madison, WI 53706. Department of Physics and Astronomy, University of Hawaii, 2505 Correa Road, Honolulu, HI 96822. Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822. Laboratory for High Energy Astrophysics, Goddard Space Flight Center, Code 660, NASA, Greenbelt, MD 20770. Department of Astronomy, University of Maryland, College Park, MD 20742.