Large-scale environments of narrow-line Seyfert 1 galaxies
  Studying large-scale environments of narrow-line Seyfert 1 (NLS1) galaxies
gives a new perspective on their properties, particularly their radio loudness.
The large-scale environment is believed to have an impact on the evolution and
intrinsic properties of galaxies, however, NLS1 sources have not been studied
in this context before. We have a large and diverse sample of 1341 NLS1
galaxies and three separate environment data sets constructed using Sloan
Digital Sky Survey. We use various statistical methods to investigate how the
properties of NLS1 galaxies are connected to the large-scale environment, and
compare the large-scale environments of NLS1 galaxies with other active galacic
nuclei (AGN) classes, for example, other jetted AGN and broad-line Seyfert 1
(BLS1) galaxies, to study how they are related. NLS1 galaxies reside in less
dense environments than any of the comparison samples, thus confirming their
young age. The average large-scale environment density and environmental
distribution of NLS1 sources is clearly different compared to BLS1 galaxies,
thus it is improbable that they could be the parent population of NLS1 galaxies
and unified by orientation. Within the NLS1 class there is a trend of
increasing radio loudness with increasing large-scale environment density,
indicating that the large-scale environment affects their intrinsic properties.
Our results suggest that the NLS1 class of sources is not homogeneous, and
furthermore, a considerable fraction of them are misclassified. We further
support a published proposal to replace the traditional classification to
radio-loud, and radio-quiet or radio-silent sources with a division to jetted
and non-jetted sources.
