Evidence for Jet Domination of the Nuclear Radio Emission in Low-Luminosity Active Galactic Nuclei

Abstract

We present simultaneous, sub-arcsecond ( = 10^{-5} L_Edd, or ADAFs with strong (p >= 0.6) outflows. The jet interpretation is favored by three factors: a) the detection of pc-scale radio extensions, morphologically reminiscent of jets, in the five nuclei with the highest peak radio flux-density; b) the domination of parsec-scale jet radio emission over unresolved `core' emission in the three best-studied nuclei; and c) the lack of any clear correlation between radio spectral shape and black hole mass as would be expected from the dependence of the radio turnover frequency on black hole mass in ADAF and CDAF models. A jet domination of nuclear radio emission implies significantly lower accretion rates in ADAF-type models than earlier estimated from core radio luminosities.