Radio properties of a large sample of narrow line Seyfert 1 galaxies

Narrow-line Seyfert 1 galaxies (NLS1) are thought to contain highly-accreting but lower-mass supermassive black hole. Their radio properties are quite diverse, ranging from extremely bright, relativistically-beamed compact jetted sources to those having extended kpc-scale emission. Recently, a large catalog of SDSS-observed NLS1 and a companion database of broad-line Seyfert 1 galaxies (BLS1) were published by Paliya et al. (2024). To study the radio properties of the sample, we cross-matched these with the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) survey and the Very Large Array Sky Survey (VLASS) databases. For the objects detected in both radio surveys, we calculated their spectral index between 1.4 and 3 GHz. We found that the distribution of spectral indices differ for the two groups with BLS1 having on average flatter radio spectra than NLS1. We further analysed radio power and radio loudness distributions to ascertain the origin of the radio emission.