Fermi Gamma-ray Space Telescope

A panchromatic view of relativistic jets in gamma-ray emitting narrow-line Seyfert 1 galaxies

Filippo D'Ammando
M. Orienti, J. Finke, M. Giroletti, J. Larsson on behalf of the Fermi Large Area Telescope Collaboration and C. M. Raiteri

Abstract:

Before the launch of the Fermi satellite only two classes of AGN were known to generate relativistic jets and thus to emit up to the gamma-ray energy range: blazars and radio galaxies, both hosted in giant elliptical galaxies. The first four 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 that NLSy1s are thought to be hosted in spiral galaxies, this finding poses intriguing questions about the nature of these objects, the knowledge of the development of relativistic jets, and the evolution of radio-loud AGN. In this context the study of the radio-loud NLSy1s from radio to gamma rays has received increasing attention. Here, we report on a systematic investigation of the properties of a large sample of radio-loud NLSy1 at MeV-GeV photon energies from the 68-month sample of Fermi-LAT data using the new Pass 8 event selection and instrument response function, investigating also in detail spectral and flux variability of the brightest sources. In addition we discuss the radio-to-gamma-rays properties of the gamma-ray emitting NLSy1s in the context of the blazar scenario and the unification of relativistic jets at different scales.