AAS 195th Meeting, January 2000
Session 17. Quasars, QSO's and Their Environments
Display, Wednesday, January 12, 2000, 9:20am-6:30pm, Grand Hall

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[17.03] Quasar Candidates in the Hubble Deep Field South

E. Monier, A. Conti, P. Osmer (OSU), J. Kennefick (Oxford), P. Hall (Toronto), M. Smith (CTIO/NOAO)

We present preliminary results of a multicolor search for faint quasars in the Hubble Deep Field South (HDF-S) using the publicly available HDF-S source catalogs and deep, ground-based z-band imaging obtained with the Big Throughput Camera on the CTIO 4-m. The four HST-WFPC2 filters were used to select quasar candidates with z < 5. At higher redshifts, the z-band data are invaluable for distinguishing quasars from late-type stars, as demonstrated by the results of the Sloan Digital Sky Survey. Point sources (CLASS>0.90) were selected from the HST-WFPC2 F300W (U), F450W (B), F606W (V) and F814W (I) filter object catalogs. The z-band catalog was produced using the FOCAS/SKICAT package to detect and classify objects. Synthetic quasar spectra were generated with 1.0 < z < 5.5 and included effects of intrinsic emission lines and absorption by Ly-alpha forest and Lyman-limit systems. From these computed quasar colors, we identify areas in the multicolor space where quasars might be found and overlay them on the data to select candidates. At the lowest redshifts (z < 2.2), quasars can be selected in the U and B images by adopting the standard UV-excess technique. As Ly-alpha moves into the V filter, quasars at z > 3.5 can be selected based on their (B-V) colors. For quasars at z > 4.8, Ly-alpha moves into the I filter, continuum absorption by Ly-alpha becomes stronger, and the (V-I) color serves as a powerful selector. As redshifts exceed z ~ 5, late type stars of similar (V-I) color will become progressively redder in (I-z) relative to quasars, allowing for the separation of quasars from stars.

The author(s) of this abstract have provided an email address for comments about the abstract: monier@astronomy.ohio-state.edu

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