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EVN observations of low-luminosity flat-spectrum AGNs

A. Caccianiga·M. J. M. Marcha·A. Thean·J. Dennett-Thorpe
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Abstract

We present and discuss the results of VLBI (EVN) observations of three low-luminosity (P(5 GHz)<10^25 W/Hz) Broad Emission Line AGNs carefully selected from a sample of flat spectrum radio sources (CLASS). Based on the total and the extended radio power at 5 GHz and at 1.4 GHz respectively, these objects should be technically classified as radio-quiet AGN and thus the origin of their radio emission is not clearly understood. The VLBI observations presented in this paper have revealed compact radio cores which imply a lower limit on the brightness temperature of about 3X10^8 K. This result rules out a thermal origin for the radio emission and strongly suggests an emission mechanism similar to that observed in more powerful radio-loud AGNs. Since, by definition, the three objects show a flat (or inverted) radio spectrum between 1.4 GHz and 8.4 GHz, the observed radio emission could be relativistically beamed. Multi-epoch VLBI observations can confirm this possibility in two years time.

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A. Caccianiga, M. J. M. Marcha, A. Thean, J. Dennett-Thorpe. 2001-08-29. EVN observations of low-luminosity flat-spectrum AGNs. https://doi.org/10.1046/j.1365-8711.2001.04928.x

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