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° 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 ( \lesssim 10 ^ { 10 } K ) , we conclude these jets are mildly relativistic ( \beta \lesssim 0.3 , \delta \sim 1 - 1.5 ) and aligned at moderately small angles to the line of sight ( 10–15° ) .
The derived kinematic ages of \sim 10 ^ { 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 .