Statistical multifrequency study of narrow-line Seyfert 1 galaxies

Context. High-energy γ-rays, which are produced by powerful relativistic jets, are usually associated with blazars and radio galaxies. In the current active galactic nuclei (AGN) paradigm, such jets are almost exclusively launched from massive elliptical galaxies. Recently, however, Fermi/LAT detected γ-rays from a few narrow-line Seyfert 1 galaxies and thus confirmed the presence of relativistic jets in them. Since NLS1 galaxies are assumed to be young evolving AGN, they offer a unique opportunity to study the production of relativistic jets in late-type galaxies. Aims. Our aim is to estimate by which processes the emission of various kinds is produced in NLS1 galaxies and to study how emission properties are connected to other intrinsic AGN properties. Methods. We have compiled the so far largest multiwavelength database of NLS1 sources. This allowed us to explore correlations between different wavebands and source properties using, for example, Pearson and Spearman correlations and principal component analysis. We did this separately for radio-loud and radio-quiet sources. Results. Multiwavelength correlations suggest that radio-loud sources host relativistic jets that are the predominant sources of radio, optical, and X-ray emission. The origin of infrared emission remains unclear. Radio-quiet sources do not host a jet, or the jet is very weak. In them, radio and infrared emission is more likely generated via star formation processes, and the optical and X-ray emission originate in the inner parts of the AGN. We also find that the black hole mass correlates significantly with radio loudness, which suggests that NLS1 galaxies with more massive black holes are more likely to be able to launch powerful relativistic jets.