Astron. J., 122, 518-535 (2001/August-0)
The large bright quasar survey. VII. The LBQS and FIRST surveys.
HEWETT P.C., FOLTZ C.B. and CHAFFEE F.H.
Abstract (from CDS):
The source catalog for the Large Bright Quasar Survey (LBQS) and the FIRST Survey are compared in their regions of overlap to assess the efficiency of the LBQS selection algorithms. In the 270 deg2 common to both surveys, the LBQS contains ≃100,000 stellar and ≃40,000 nonstellar objects, while the FIRST catalog contains ≃25,000 sources. Cross-correlation of these lists yields 67 positional coincidences between known LBQS quasars and FIRST sources and an additional 19 stellar and 149 nonstellar positional coincidences with the radio catalog. Spectroscopy of all the stellar matches and two-thirds of the nonstellar matches using the Keck I Telescope and the 6.5 m MMT produces eight new quasars. One BL Lac object, previously misclassified during the LBQS survey is also identified. The straightforward fractional incompleteness of the LBQS determined from this sample is 13%±4%, in good agreement with the published estimate of 10%. Furthermore, four of the nine new objects have redshifts in the range z=0.7-1.0, a redshift region in which the LBQS selection is known to have decreased efficiency. The distributions of the ratio of radio-to-optical power, apparent magnitude, and spectroscopic properties for the new objects are consistent with those of the 67 LBQS-FIRST objects previously known. The consistency of the optical and radio properties of the new objects with those of the known quasars thus supports the conclusion that no new population of objects, constituting more than ≃7% of quasars detected by FIRST, has eluded the LBQS optical selection techniques. The percentage of radio-detected quasars in the LBQS catalog is found to be 12%±2%, considerably smaller than the value of 25% advocated by White et al. (published in 2000) based on the First Bright Quasar Survey (FBQS). Apparent differences in the form of the number-redshift relation for the LBQS and FBQS samples are shown to arise in large part from the very different optical passbands used in the compilation of the surveys.
Galaxies: Quasars: General - Surveys
VizieR on-line data:
<Available at CDS (J/AJ/122/518): table1.dat table2.dat table3.dat table4.dat table5.dat>
Tables 1-2: LBQS HHMM+DDMMA N=12+75.
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