Inner jet kinematics and the viewing angle towards the {\gamma}-ray narrow-line Seyfert 1 galaxy 1H 0323+342

TL;DR

This study uses multi-epoch VLBA imaging and radio monitoring to measure jet speeds and variability, constraining the viewing angles of the NLS1 galaxy 1H 0323+342 and similar sources, shedding light on their orientation and jet physics.

Contribution

It provides the first detailed measurement of the viewing angle for 1H 0323+342 using combined VLBA and variability data, advancing understanding of NLS1 AGN orientation.

Findings

Jet components exhibit apparent speeds of 1 to 7 times the speed of light.

The viewing angle towards 1H 0323+342 is constrained to 4-13 degrees.

Similar sources have estimated viewing angles of 8-9 degrees.

Abstract

Near-Eddington accretion rates onto low-mass black holes are thought to be a prime driver of the multi-wavelength properties of the narrow-line Seyfert 1 (NLS1) population of active galactic nuclei (AGN). Orientation effects have repeatedly been considered as another important factor involved, but detailed studies have been hampered by the lack of measured viewing angles towards this type of AGN. Here we present multi-epoch, 15 GHz VLBA images (MOJAVE program) of the radio-loud and Fermi/LAT-detected NLS1 galaxy 1H 323+342. These are combined with single-dish, multi-frequency radio monitoring of the source's variability, obtained with the Effelsberg 100-m and IRAM 30-m telescopes, in the course of the F-GAMMA program. The VLBA images reveal 6 components with apparent peeds of ~1 to ~7 c, and one quasi-stationary feature. Combining the obtained apparent jet speed ($\beta_{app}$) and variability Doppler factor ($D_{var}$) estimates together with other methods, we constrain the viewing angle towards 1H 0323+342 to $\theta \leq 4 - 13$ deg. Using literature values of $\beta_{app}$ and $D_{var}$, we also deduce a viewing angle of $\leq$ 8-9 deg towards another radio- and {\gamma}-ray-loud NLS1, namely SBS 0846+513.