Is J 133658.3-295105 a Radio Source at z >= 1.0 or at the Distance of M 83?

TL;DR

This study investigates the nature and distance of the radio source J 133658.3-295105, presenting optical imaging and spectroscopy that suggest it may be at a higher redshift than previously thought or ejected from M 83.

Contribution

The paper provides new spectroscopic data and proposes two scenarios for the radio source's distance, challenging prior assumptions about its redshift and origin.

Findings

Detected redshifted H_alpha emission near the source

No other emission lines detected down to magnitude limit

Proposes the source is at z >= 2.5 or ejected from M 83

Abstract

We present Gemini optical imaging and spectroscopy of the radio source J 133658.3-295105. This source has been suggested to be the core of an FR II radio source with two detected lobes. J 133658.3-295105 and its lobes are aligned with the optical nucleus of M 83 and with three other radio sources at the M 83 bulge outer region. These radio sources are neither supernova remnants nor H II regions. This curious configuration prompted us to try to determine the distance to J 133658.3-295105. We detected H_alpha emission redshifted by ~ 130 km s^-1 with respect to an M 83 H II region 2.5" east-southeast of the radio source. We do not detect other redshifted emission lines of an optical counterpart down to m_i = 22.2 +/- 0.8. Two different scenarios are proposed: the radio source is at z >= 2.5, a much larger distance than the previously proposed lower limit z >= 1.0, or the object was ejected by a gravitational recoil event from the M 83 nucleus. This nucleus is undergoing a strong dynamical evolution, judging from previous three-dimensional spectroscopy.