http://arxiv.org/abs/1712.01799
The detection of several radio-loud narrow-line Seyfert 1 (NLS1) galaxies by the Fermi Gamma-Ray Space Telescope hints at the existence of a rare, new class of gamma-ray emitting active galactic nuclei with low black hole masses. Like flat spectrum radio quasars (FSRQs), their gamma-ray emission is thought to be produced via the external Compton mechanism whereby relativistic jet electrons upscatter a photon field external to the jet, e.g. from the accretion disc, broad line region (BLR) and dusty torus, to higher energies. Here we study the origin of the gamma-ray emission in the lowest-redshift candidate among the currently-known gamma-ray emitting NLS1s, 1H 0323+342, and take a new approach. We observationally constrain the external photon field using quasi-simultaneous near-IR, optical and X-ray spectroscopy. Applying a one-zone leptonic jet model, we simulate the range of jet parameters for which this photon field, when Compton scattered to higher energies, can explain the gamma-ray emission. We find that the site of the gamma-ray emission lies well within the BLR and that the seed photons mainly originate from the accretion disc. The jet power that we determine, $1.0 \times 10^{45}$ erg s$^{-1}$, is approximately half the accretion disc luminosity. We show that this object is not simply a low-mass FSRQ, its jet is intrinsically less powerful than predicted by scaling a typical FSRQ jet by black hole mass and accretion rate. That gamma-ray emitting NLS1s appear to host underpowered jets may go some way to explaining why so few have been detected to date.
D. Kynoch, H. Landt, M. Ward, et. al.
Wed, 6 Dec 17
4/71
Comments: 22 pages, 8 figures and 8 tables. Accepted for publication in MNRAS