Nuclear Luminosities and Radio Loudness of Seyfert Nuclei

Abstract

Historically, Seyfert nuclei have been considered to be radio-quiet active galactic nuclei (AGNs). We question this widely held assumption by showing that the distribution of the radio-to-optical luminosity ratio, R≡L_ν(6 cm)/L_ν(B), when properly measured for the nuclear component, places the majority of type 1 Seyfert nuclei in the category of radio-loud AGNs, defined here as objects with R>=10. This result is further strengthened by strong correlations found between radio power and optical continuum and emission-line luminosities, as has been established previously for more powerful AGNs. We also present a new calibration of the relation between optical continuum and Balmer emission-line luminosities valid in the regime of low-luminosity AGNs.