Kiloparsec-scale jets in three radio-loud narrow-line Seyfert 1 galaxies

TL;DR

This study reports the discovery of kiloparsec-scale jets in three radio-loud narrow-line Seyfert 1 galaxies, revealing their morphology, kinematics, and possible evolutionary stage, thus expanding understanding of jet phenomena in these galaxies.

Contribution

First detailed analysis of kiloparsec-scale jets in multiple radio-loud NLS1s, showing their morphology, relativistic properties, and implications for galaxy evolution.

Findings

Jets are mildly relativistic and aligned at small angles to the line of sight.

Extended radio emission spans 20-70 kpc with FR II-like morphology.

Kinematic ages are 10^6 to 10^7 years, younger than typical radio galaxies.

Abstract

We have discovered kiloparsec-scale extended radio emission in three narrow-line Seyfert 1 galaxies (NLS1s) in sub-arcsecond resolution 9 GHz images from the Karl G. Jansky Very Large Array (VLA). We find all sources show two-sided, mildly core-dominated jet structures with diffuse lobes dominated by termination hotspots. These span 20-70 kpc with morphologies reminiscent of FR II radio galaxies, while the extended radio luminosities are intermediate between FR I and FR II sources. In two cases the structure is linear, while a $45^{\circ}$ bend is apparent in the third. Very Long Baseline Array images at 7.6 GHz reveal parsec-scale jet structures, in two cases with extended structure aligned with the inner regions of the kiloparsec-scale jets. Based on this alignment, the ratio of the radio core luminosity to the optical luminosity, the jet/counter-jet intensity and extension length ratios, and moderate core brightness temperatures ($\lesssim10^{10}$ K), we conclude these jets are mildly relativistic ($\beta\lesssim0.3$, $\delta\sim1$-$1.5$) and aligned at moderately small angles to the line of sight (10-15$^{\circ}$). The derived kinematic ages of $\sim10^6$-$10^7$ y are much younger than radio galaxies but comparable to other NLS1s. Our results increase the number of radio-loud NLS1s with known kiloparsec-scale extensions from seven to ten and suggest that such extended emission may be common, at least among the brightest of these sources.