The curious case of narrow-line Seyfert 1 galaxies in radio

Narrow-line Seyfert 1 galaxies (NLS1s) are a peculiar bunch of active galactic nuclei (AGN). These sources are characterized by their optical spectral properties: full width at half maximum (FWHM) of the broad Hb emission line being a maximum of 2000 km s^(-1), and (S[O III]/S(Hb) < 3). Due to these sources being identified based on their optical properties, they are rather unified from an optical perspective. However, due to their spectra occasionally resembling those of other sources, especially when using low-quality data, NLS1s are frequently misclassified. This study uses the largest clean sample available of NLS1s with 3998 sources. In this study, these nearly 4000 sources were studied at three radio frequencies: 144~MHz, 1.4~GHz, and 3~GHz. Originally, it was believed that these sources could not harbor significant radio emission, however, these sources have been proven to be capable of launching and maintaining powerful relativistic jets, thus showcasing significant radio emission. Although NLS1s are quite unified from the optical perspective, their behavior in radio is anything but unified. Nearly half of the sample has been detected at the used frequencies, with some of the sources having Jy-level detections. This study also includes analysis of the spectral index, radio luminosity, and general optical spectral properties of the sample. With this study, it is finally possible to study the population-wide characteristics of NLS1s in radio.