Four Years of Fermi LAT Observations of Narrow-Line Seyfert 1 Galaxies
  Before the launch of the Fermi satellite only two classes of AGN were known
to generate relativistic jets and thus emit up to the gamma-ray energy range:
blazars and radio galaxies, both hosted in giant elliptical galaxies. The first
two years of observations by the Large Area Telescope (LAT) on board Fermi
confirmed that these two are the most numerous classes of identified sources in
the extragalactic gamma-ray sky, but the discovery of variable gamma-ray
emission from 5 radio-loud Narrow-Line Seyfert 1 galaxies (NLSy1s) revealed the
presence of a possible emerging third class of AGN with relativistic jets.
Considering also that NLSy1s are typically hosted in spiral galaxy, this
finding poses intriguing questions about the nature of these objects, the onset
of production of relativistic jets, and the cosmological evolution of
radio-loud AGN. Here, we report on a preliminary investigation of the
properties of this sample of radio-loud NLSy1 at MeV-GeV photon energies,
utilizing the four-year accumulation of Fermi LAT data. In addition we briefly
discuss some radio-to-gamma-rays properties of the gamma-ray emitting NLSy1 in
the context of the blazar scenario.
