Statistical multifrequency study of narrow-line Seyfert 1 galaxies
  High-energy {\gamma}-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
{\gamma}-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. 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.
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. 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.
