The radio structure of the narrow-line Seyfert 1 Mrk 783 with VLBA and e-MERLIN

Abstract

In this paper, we present the analysis of new radio and optical observations of the narrow-line Seyfert 1 galaxy Mrk 783. 1.6 GHz observations performed with the e-MERLIN interferometer confirm the presence of the diffuse emission previously observed. The Very Long Baseline Array (VLBA) also detects the nuclear source both at 1.6 GHz (L band) and 5GHz (C band). While the L-band image shows only an unresolved core, the C-band image shows the presence of a partially resolved structure at a position angle of 60 deg. The brightness temperature of the emission in both bands ( >10^6 K ) suggests that it is a pc-scale jet produced by the active galactic nucleus. The relatively steep VLBA spectral index (α_VLBA</SUB> = 0.63 ± 0.03) is consistent with the presence of optically thin emission on milliarcsecond scales. Finally, we investigated two possible scenarios that can result in the misalignment between the kpc and pc-scale radio structure detected in the galaxy. We also analysed the optical morphology of the galaxy, which suggests that Mrk 783 underwent a merging in relatively recent times.