Modelling the compact and extended jet emission regions in gamma-ray emitting Narrow-line Seyfert 1 galaxies

ABSTRACT We investigate the energetics and emission properties of relativistic jets in gamma-ray emitting Narrow-Line Seyfert 1 (NLS1) galaxies by using a composite model that includes both a compact jet region and an extended radio-jet component. Standard one-zone models, which assume a single homogeneous emission region, often struggle to reproduce the low-frequency radio emission from large-scale jet structures and can yield inaccurate estimates of key physical parameters. Incorporating the radio-jet component allows for a more comprehensive spectral energy distribution (SED) fit, allowing for improved constraints on critical parameters such as the minimum electron Lorentz factor $\gamma _\mathrm{min}$, electron density, magnetic field strength, and kinetic power. This approach ensures a more realistic jet power budget by limiting the contribution from cold protons, which is crucial for self-consistent energetics. Furthermore, comparing jet powers derived from SED fits with those predicted by the Blandford–Znajek mechanism reveals its insufficiency in explaining the full jet power in high-accretion NLS1s, suggesting the need for additional jet launching processes like the Blandford–Payne mechanism or hybrid models. Our findings emphasize the importance of multicomponent modelling and complex jet geometries to accurately capture the physical conditions and emission mechanisms in relativistic jets of gamma-ray emitting NLS1s.