A $\gamma$-Ray Emitting Blazar at Redshift 3.64: Fermi-LAT and OVRO Observations of PKS 0201+113

TL;DR

This paper reports the discovery and analysis of a high-redshift gamma-ray blazar, PKS 0201+113, using Fermi-LAT and OVRO data, revealing its jet properties and flaring activity, and providing insights into early universe black hole growth.

Contribution

It presents the first detection of quasi-simultaneous gamma-ray and radio flares in a z>3.5 blazar, with detailed modeling of its jet emission and properties.

Findings

PKS 0201+113 is only the third gamma-ray blazar at z>3.5.

A significant gamma-ray source was identified with a 5σ detection.

Radio and gamma-ray flares are temporally associated, indicating linked emission regions.

Abstract

High-redshift ($z >3$) $\gamma$-ray blazars are rare, but they are crucial for our understanding of jet evolution, $\gamma$-ray production and propagation, and the growth of supermassive black holes in the early universe. A new analysis of Fermi-LAT data reveals a significant (5$\sigma$), spectrally soft ($\Gamma \simeq$ 3.0) $\gamma$-ray source in a specific 4-month epoch, cospatial with PKS 0201+113 ($z$ = 3.64). Monitoring of PKS 0201+113 at 15 GHz by the Owens Valley Radio Observatory 40 m Telescope from 2008 to 2023 shows a prominent flare that dominates the radio light curve. The maximum of the radio flare coincides with the $\gamma$-ray flare, strongly suggesting an association ($\textrm{p-value}=0.023$) between the $\gamma$-ray and the radio sources. PKS 0201+113 is only the third $\gamma$-ray blazar to be identified with $z> 3.5$, and it is the first such object to be identified by the detection of quasi-simultaneous $\gamma$-ray and radio flares. The jet properties of this peculiar blazar have been investigated. A detailed study of a two-zone leptonic model is presented that fits the broadband spectral energy distribution. An alternative scenario is also briefly discussed.