Falcke et al., Boosted Radio-Weak Quasars
EVN+MERLIN Observations of Radio-Intermediate Quasars: Evidence
for Boosted Radio-Reak Quasars
Heino Falcke(1), Alok Patnaik(2), William Sherwood(2)
(1) Department of Astronomy, University of Maryland, College Park, MD 20742-2421
(2) Max-Planck Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany
The Astrophysical Journal Letters, Vol. 473, L13-L16
We present VLBI (EVN+MERLIN) observations of a sample of three
low-redshift radio-intermediate PG quasars (RIQ) with flat and
variable radio spectrum (III Zw 2, PG 1309+355, PG 2209+184). Their
radio-to-optical flux ratio (R) is slightly lower than the average
R for steep-spectrum quasars, but their radio spectral properties are
those of core-dominated quasars. It was proposed previously that these
sources might be relativistically boosted jets in radio-weak quasars.
Our VLBI observations now indeed confirm the presence of a high
brightness temperature core in all three of these objects --- two of
them have lower limits on TB well in excess of 1010
Kelvin. Moreover, we find no ``missing-flux'' which means that
basically all the flux of these quasars is concentrated in the compact
radio core. As the total radio flux is already at the low end for
radio-loud quasars, we can place a strong limit on the presence of any
extended emission. This limit is consistent with the extended
emission in radio-weak quasars, but excludes that the flat-spectrum
RIQ reside in typical radio-loud quasars. The observations therefore
strongly support the idea that relativistic jets are present in
radio-weak quasars and hence that radio-loud and radio-weak quasars
have very similar central engines.
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