FERMI/LARGE AREA TELESCOPE DISCOVERY OF GAMMA-RAY EMISSION FROM A RELATIVISTIC JET IN THE NARROW-LINE QUASAR PMN J0948+0022

Abstract

We report the discovery by the Large Area Telescope (LAT) onboard the Fermi Gamma-Ray Space Telescope of high-energy γ-ray emission from the peculiar quasar PMN J0948+0022 (z = 0.5846). The optical spectrum of this object exhibits rather narrow Hβ (FWHM(Hβ) ∼1500 km s −1), weak forbidden lines, and is therefore classified as a narrow-line type I quasar. This class of objects is thought to have relatively small black hole mass and to accrete at a high Eddington ratio. The radio loudness and variability of the compact radio core indicate the presence of a relativistic jet. Quasi-simultaneous radio/optical/X-ray and γ-ray observations are presented. Both radio and γ-ray emissions (observed over five months) are strongly variable. The simultaneous optical and X-ray data from Swift show a blue continuum attributed to the accretion disk and a hard X-ray spectrum attributed to the jet. The resulting broadband spectral energy distribution (SED) and, in particular, the γ-ray spectrum measured by Fermi are similar to those of more powerful Flat-Spectrum Radio Quasars (FSRQs). A comparison of the radio and γ-ray characteristics of PMN J0948+0022 with the other blazars detected by LAT shows that this source has a relatively low radio and γ-ray power with respect to other FSRQs. The physical parameters obtained from modeling the SED also fall at the low power end of the FSRQ parameter region discussed in Celotti & Ghisellini. We suggest that the similarity of the SED of PMN J0948+0022 to that of more massive and more powerful quasars can be understood in a scenario in which the SED properties depend on the Eddington ratio rather than on the absolute power.

Properties of flat-spectrum radio-loud narrow-line Seyfert 1 galaxies

“…An important new discovery made with the Large Area Telescope (LAT, Atwood et al 2009) on board the Fermi Gamma-ray Space Telescope (hereafter Fermi) is the high-energy gammaray emission from radio-loud narrow-line Seyfert 1 galaxies (RLNLS1s, Abdo et al 2009a,b,c, Foschini et al 2010. Narrow-line Seyfert 1 galaxies (NLS1s) are a well-known class of active galactic nuclei (AGNs), but they are usually considered to be radio-quiet (e.g.…”

The gamma-ray emitting radio-loud narrow-line Seyfert 1 galaxy PKS 2004−447

“…The radio-loud versions of narrow-line Seyfert 1 (RL-NLS1) galaxies have attracted growing interest in recent years, especially since Abdo et al (2009a) reported detecting γ-ray emission from PMN J0948+0022 with the LAT instrument on-board the Fermi γ-ray satellite (Atwood et al 2009). NLS1 galaxies harbour an active galactic nucleus (AGN) that exhibits both broad and narrow emission lines as in typical type-1 AGNs.…”

TANAMI: Multiwavelength and multimessenger observations of active galaxies

“…A new class of γ-ray emitting AGN detected by Fermi /LAT are radio-loud Narrow-Line Seyfert 1 Galaxies (RLNL-Sy 1s, Abdo et al 2009b;Abdo et al 2009c). VLBI observations of PMN J 0948+0022 (Abdo et al 2009d;Giroletti et al 2011) have demonstrated that this source has a high-brightness-temperature radio core, suggesting www.an-journal.org that the γ-ray emission of Fermi /LAT-detected RLNL-Sy 1s is coupled to the presence of relativistically beamed jets as in blazars, but harboured in spiral rather than elliptical galaxies and originating from the environment of supermassive black holes with relatively low-masses (Foschini et al 2013).…”