Identifying Radio-active Galactic Nuclei among Radio-emitting Galaxies

Basing our analysis on ROGUE I, a catalog of over 32,000 radio sources associated with optical galaxies, we provide two diagnostics to select the galaxies where emission is dominated by an active galactic nucleus (AGN), referred in paper as radio-AGNs. Each these can be applied independently. The first one, dubbed MIRAD, compares flux FW3 W3 mid-infrared band Wide-field Infrared Survey Explorer telescope, at 1.4 GHz, F1.4. MIRAD requires no spectra. second diagnostic, DLM, 4000 Å break strength, Dn(4000), luminosity per unit stellar mass. DLM diagram has already been used past, but not stand-alone. For diagrams, propose simple, empirical dividing lines that result same classification for objects common. These correctly classify radio-AGN 99.5% extended I catalog, and star-forming 98%–99% identified such their emission-line ratios. Both diagrams clearly show radio-AGNs are preferentially found among elliptical hosting most massive black holes. Most classified or either optically weak AGNs retired galaxies.