Is 3C 111, an apparently normal radio galaxy, the counterpart of 3EG J0416+3650?

¹ School of Physics and Astronomy, University of Southampton, Highfield, Southampton, SO17 1BJ, UK e-mail: sguera@astro.soton.ac.uk
² IASF/CNR, via Piero Gobetti 101, 40129 Bologna, Italy

Received: 2 August 2004
Accepted: 20 September 2004

Abstract

The Third EGRET Catalog (3EG) lists 66 high-confidence identifications of sources with Active Galactic Nuclei (AGN). All are classified as belonging to the blazar class, with the only exception of the nearby radio galaxy Centaurus A. We report and strengthen the association of another radio galaxy, 3C 111, with the EGRET source 3EG J0416+3650. At the time of the compilation of the 3EG catalogue, 3C 111 has been considered as a low-confidence counterpart of 3EG J0416+3650, being located outside the 99% γ-ray probability contour. Since this first suggestion, no other counterparts have been reported nor the EGRET error box has been searched for likely candidates. 3C 111 has never been considerated or cited in literature as a radiogalaxy counterpart of an EGRET source. We report a detailed multiwavelength study of the EGRET error box as well as for the first time the overall spectral energy distribution of 3C 111, which appears to be intriguingly similar to those of blazars, suggesting that the radiogalaxy 3C 111 is the likely counterpart of 3EG J0416+3650.