Quasar Candidates in the Hubble Deep Field

We focus on the search for unresolved faint quasars and AGN in the crudecombine images using a multicolor imaging analysis that has proven verysuccessful in recent years. Quasar selection was carried out both in multicolorspace and in "profile space," defined as the multi-parameter space formed bythe radial profiles of the objects in the different images. By combining thedither frames available for each filter, we were able to obtain well-sampledradial profiles of the objects and measure their deviation from that of astellar source. We also generated synthetic quasar spectra in the range 1.0 < z< 5.5 and computed expected quasar colors. We determined that the data are 90%complete for point sources at 26.2, 28.0, 27.8, 26.8 in the F300W, F450W, F606Wand F814W filters, respectively. We find 41 compact objects in the HDF: 8pointlike objects with colors consistent with quasars or stars, 18 stars, and15 slightly resolved objects, 12 of which have colors consistent with quasarsor stars. We estimate the upper limit of unresolved and slightly resolvedquasars/AGNs with V < 27.0 and z < 3.5 to be 20 objects (16,200 per deg^2). Wefind good agreement among authors on the number of stars and the lack of quasarcandidates with z > 3.5. We find more quasar candidates than previous workbecause of our more extensive modeling and use of all of the available colorinformation. (abridged)Comment: We have clarified our discussion and conclusions, added some references and removed the appendix, which is now available from the first author. 37 pages including 10 embedded postscript figures and 6 tables. To appear in the Feb. 99 issue of A