A Deep ROSAT Survey of the Lynx.3A Region
Session 74 -- Clusters of Galaxies II: X-Rays
Display presentation, Wednesday, 11, 1995, 9:20am - 6:30pm

## [74.10] A Deep ROSAT Survey of the Lynx.3A Region

D. F. Mathis, R. A. Windhorst, D. Burstein, B. E. Franklin (ASU), S. F. Anderson (U.Wash.), T. Maccacaro (Osservatorio Astronomico di Brera), R. E. Griffiths, L. W. Neuschaefer (JHU), W. A. Morgan (PSU), D. C. Koo, C. Gronwall (UCSC), C. N. A. Willmer (DAN Observatorio Nacional)

We present the results of a deep ROSAT survey in the Leiden Berkeley Deep Survey field Lynx.3A, which has low $N_H$ and $E_{B-V}$. It has been well studied from the ground through deep Westerbork surveys (down to 17 $\mu$Jy at 1.4 GHz) {\it and} with the Palomar 200 inch Four-shooter CCD-array through a large contiguous mosaic in Gunn $gri$ with 90\% completeness to $B_J\sim$25.5 mag (Neuschaefer \& Windhorst 1995, ApJ 439, 000, in press).

We present the most likely optical candidates for the X-ray sources, as followed-up with the Kitt Peak 4 meter HYDRA multi-fiber and the Multiple Mirror Telescope's Red Channel spectrographs. Most ROSAT sources are stellar, and about two thirds of these have Gunn $gri$ colors typical of QSO's. The remainder are red objects, presumably X-ray stars. We also found a few compact galaxy ids, or galaxies in a group.

We also present the 0.5-2.0 keV source counts. At the bright end, the observed ROSAT/Lynx X-ray source counts have a slope and amplitude consistent with those of the Einstein Medium Sensitivity (EMSS) and Deep Surveys. At around $S_X \sim 10^{-14}$ cgs, our counts appear to flatten, in agreement with the results of two other ROSAT deep surveys. Below this level and down to our 3.5$\sigma$ completeness limit, the observed counts have a slope of 1.1$\pm$0.2. After correction for Eddington bias", our inferred intrinsic slope is 0.9$\pm$0.2, (at least marginally) flatter than the EMSS slope of 1.48$\pm$0.05 appropriate at brighter X-ray fluxes.

Our sample will be used to determine the AGN contribution to the XRB, as well as that of non-AGN (e.g. starburst and/or radio galaxies), and to constrain the evolution in radio--optical--X-ray of the primary X-ray population (AGN). This research is supported by NASA/ROSAT grant NAG-1455 and 2322.