Jet Radiation Properties of 4C +49.22: from the Core to Large-Scale Knots

TL;DR

This study analyzes the spectral energy distributions of the core and large-scale knots in quasar 4C +49.22, revealing jet deceleration, magnetic energy conversion, and potential contributions to steady gamma-ray emission.

Contribution

It provides a comprehensive leptonic model analysis of both core and large-scale jet regions, linking gamma-ray emission to jet dynamics and energetics.

Findings

Gamma-ray emission includes a steady component from large-scale knots.

Magnetization decreases from core to knots, indicating energy conversion.

Jet decelerates and transitions from magnetized to particle-dominated.

Abstract

4C +49.22 is a gamma-ray flat spectrum radio quasar with a bright and knotty jet. We investigate the properties of the core and large-scale knots by using their spectral energy distributions (SEDs). Analyzing its Fermi/LAT data in the past 8 years, a long-term steady gamma-ray emission component is found besides bright outbursts. For the core region, the gamma-ray emission together with the simultaneous emission in the low-energy bands at different epochs is explained with the single-zone leptonic model. The derived magnetization parameters and radiation efficiencies of the radio-core jet decrease as gamma-ray flux decays, likely indicating that a large part of the magnetic energy is converted to the kinetic energy of particles in pc-scale. For the large-scale knots, their radio-optical-X-ray SEDs can be reproduced with the leptonic model by considering the inverse Compton scattering of cosmic microwave background photons. The sum of the predicted gamma-ray fluxes of these knots is comparable to that observed with LAT at 10^{24} Hz of the steady gamma-ray component, indicating that the steady gamma-ray emission may be partially contributed by these large-scale knots. This may conceal the flux variations of the low-level gamma-ray emission from the radio-core. The derived bulk Lorentz factors of the knots decrease along the distance to the core, illustrating as deceleration of jet in large-scale. The powers of the core and knots are roughly in the same order, but the jet changes from highly magnetized at the core region into particle-dominated at the large-scale knots.