DPOSS Identifications of Flat-Spectrum Radio Sources: Limits on the Hypotetical Population of Obscured Quasars

Details DPOSS Identifications of Flat-Spectrum Radio Sources: Limits on the Hypotetical Population of Obscured Quasars DPOSS Identifications of Flat-Spectrum Radio Sources: Limits on the Hypotetical Population of Obscured Quasars

Sep 1998

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998aas...192.5521k&link_type=abstract

American Astronomical Society, 192nd AAS Meeting, #55.21; Bulletin of the American Astronomical Society, Vol. 30, p.1152

Astronomy and Astrophysics

Astronomy

Scientific paper

We use the digitized version of the Second Palomar Sky Survey (DPOSS) to obtain optical IDs of a complete sample of several hundred unresolved, flat-spectrum (alpha > -0.5, where F_nu ~ nu (alpha ) ) radio sources, selected from the Texas, GB, and PKS radio surveys. The radio selection was designed to maximize the number of quasars, rather than radio galaxies. The DPOSS data typically reach down to the equivalent limiting magnitude of Blim ~ 22(m) . About 85% of the entire sample detected by DPOSS, but about 95% of the sources with alpha > -0.3 (more likely to be quasars) were identified. The majority of the remaining DPOSS non-detections have relatively steep spectra (alpha ~ -0.5), which is consistent with the expected radio galaxy contamination. Follow-up CCD and near-IR imaging of these empty fields at the Palomar 60-inch telescope is consistent with this interpretation: we find no extremely red, point sources. We use these results to address the possibility (proposed, e.g., by Webster et al.) that there may exist a large population of dust-obscured quasars which would have escaped detection by any non-radio-based technique. Our identification rate for point sources, and the contamination pattern by radio galaxies, suggest that at most a few percent (probably < 1%) of all radio-loud quasars can be obscured by dust.

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