Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000aas...19710804u&link_type=abstract
American Astronomical Society, 197th AAS Meeting, #108.04; Bulletin of the American Astronomical Society, Vol. 32, p.1585
Astronomy and Astrophysics
Astronomy
Scientific paper
A ``missing link'' in unified schemes for active galaxies has been the lack of a populous group of radio-quiet type 2 quasars (hereafter ``Q2s''), the more distant and powerful analogs of the narrow-lined Seyfert 2 galaxies. Recently, a population of Q2 candidates has been revealed in the redshift range 0.31 <= z <= 0.37, by means of extremely strong [O III] emission found during spectroscopic follow-up observations of the Digital POSS-II (Djorgovski et al. 1999, BAAS, 31, 1467). Nineteen Q2 candidates were observed in August 2000 using the Very Large Array in its most compact configuration, at a frequency of 8.4 GHz. Fourteen detections were achieved within 3'' of the optical positions of the candidates, with flux densities ranging from 70 μ Jy to 1500 μ Jy. The corresponding radio powers lie between 1022 and 1024 W Hz-1, implying that the Q2 candidates are radio-quiet, and overlap the upper end of the radio luminosity function for Seyfert 2 galaxies. The ratio of radio power to [O III] luminosity is consistent with the well-known relationship between those quantities for Seyfert 2 galaxies. Finally, the radio powers are consistent with those of radio-quiet quasars within the same redshift range, after allowance is made for possible differences in the radio/[O III] ratios for type 1 and type 2 objects. Therefore, the radio imaging confirms a substantial population of type 2 quasars with optically weak continua. This is consistent with the hypothesis that these objects contain a nuclear torus that is closer to edge-on than to face-on, blocking the continuum radiation that excites the powerful [O III] emission. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.
Brunner Robert J.
Djorgovski Stanislav G.
Mahabal Ashish A.
Ulvestad James S.
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