Low frequency observations at 325 and 610 MHz have been carried out for two “ radio-loud ” Seyfert galaxies , NGC 4235 and NGC 4594 ( Sombrero galaxy ) , using the Giant Meterwave Radio Telescope ( GMRT ) .
The 610 MHz total intensity and 325 - 610 MHz spectral index images of NGC 4235 tentatively suggest the presence of a “ relic ” radio lobe , most likely from a previous episode of AGN activity .
This makes NGC 4235 only the second known Seyfert galaxy after Mrk 6 to show signatures of episodic activity . Spitzer and Herschel infrared spectral energy distribution ( SED ) modelling using the clumpyDREAM code predicts star formation rates ( SFR ) that are an order of magnitude lower than those required to power the radio lobes in these Seyferts ( \sim 0.13 - 0.23 M _ { \sun } yr ^ { -1 } compared to the required SFR of \sim 2.0 - 2.7 M _ { \sun } yr ^ { -1 } in NGC 4594 and NGC 4235 , respectively ) .
This finding along with the detection of parsec and sub-kpc radio jets in both Seyfert galaxies , that are roughly along the same position angles as the radio lobes , strongly support the suggestion that Seyfert lobes are AGN-powered .
SED modelling supports the “ true ” type 2 classification of NGC 4594 : this galaxy lacks significant dust obscuration as well as a prominent broad-line region .
Between the two Seyfert galaxies , there is an inverse relation between their radio-loudness and Eddington ratio and a direct relation between their Eddington-scaled jet power and bolometric power .