# The relativistic jet of the $\gamma$-ray emitting narrow-line Seyfert 1 galaxy PKS J1222$+$0413

## TL;DR

This study presents a detailed multi-frequency analysis of the highest redshift gamma-ray emitting narrow-line Seyfert 1 galaxy PKS J1222+0413, exploring its jet and accretion properties to understand its relation to flat spectrum radio quasars.

## Contribution

It provides the first comprehensive broadband spectral energy distribution of PKS J1222+0413, combining new multi-wavelength data and physical modeling to compare its jet and black hole characteristics with FSRQs.

## Key findings

- PKS J1222+0413 has a black hole mass of about 2×10^8 solar masses.
- The galaxy's properties suggest similarities between gamma-ray NLS1s and FSRQs.
- The jet emission and accretion flow are consistent with FSRQ-like behavior.

## Abstract

We present a multi-frequency study of PKS J1222$+$0413 (4C$+$04.42), currently the highest redshift $\gamma$-ray emitting narrow-line Seyfert 1 ($\gamma$-NLS1). We assemble a broad spectral energy distribution (SED) including previously unpublished datasets: X-ray data obtained with the NuSTAR and Neil Gehrels Swift observatories; near-infrared, optical and UV spectroscopy obtained with VLT X-shooter; and multiband radio data from the Effelsberg telescope. These new observations are supplemented by archival data from the literature. We apply physical models to the broadband SED, parameterising the accretion flow and jet emission to investigate the disc-jet connection. PKS J1222$+$0413 has a much greater black hole mass than most other NLS1s, $M_\mathrm{BH}\approx2\times10^{8}$ M$_\odot$, similar to those found in flat spectrum radio quasars (FSRQs). Therefore this source provides insight into how the jets of $\gamma$-NLS1s relate to those of FSRQs.