3C403: a candidate neutrino-emitting radio galaxy

TL;DR

3C403, a radio galaxy with a stable, misaligned jet, is a promising candidate for high-energy neutrino emission, providing insights into the connection between accretion, jet activity, and neutrino production.

Contribution

This study identifies 3C403 as a significant neutrino candidate and investigates its jet and accretion properties to understand neutrino emission mechanisms.

Findings

3C403 is the second most significant neutrino source among 150+ examined.

It has a stable, two-sided jet with no strong Doppler boosting.

Current neutrino flux limits prevent definitive conclusions about its neutrino emission relation.

Abstract

3C403 is a well-known FRII radio galaxy with jets extending up to kiloparsec scales. We report its identification as the second most significant candidate among more than 150 sources examined using the 15-year neutrino dataset from the ANTARES Collaboration, making it one of the most promising radio-galaxy candidates for high-energy neutrino emission. Motivated by previous associations between blazars and neutrino events, we investigated the jet properties of 3C403 and their possible role in neutrino production. Multi-scale radio observations, from parsec to kiloparsec scales, reveal a stable, two-sided jet lying close to the plane of the sky, with no evidence of strong Doppler boosting, while X-ray data indicate a dominant, heavily absorbed accretion-related component. We also examined the recently proposed correlation between neutrino and hard X-ray fluxes - originally identified in blazars and Seyfert galaxies - and find that 3C403 occupies an intermediate location in the $L_{\nu}$--$L_{\rm hX}$ plane between jet-dominated and corona-dominated systems. However, the current upper limit on its neutrino flux prevents a firm assessment of whether it follows the proposed relation. With radiatively efficient accretion ($\lambda_{\rm Edd}\sim10^{-2}$), strong hard X-ray emission, and a powerful but misaligned jet, 3C403 provides a physically motivated laboratory for exploring the interplay between coronal activity and jet environments in multimessenger scenarios of neutrino production in active galaxies.