The innermost region of the water megamaser radio galaxy 3C403

TL;DR

This study investigates the nuclear environment of the radio galaxy 3C403 using high-resolution radio observations, revealing details about its gas and dust content and the presence of water megamaser emission.

Contribution

It provides the first high-resolution observations of the innermost regions of 3C403, combining maser, continuum, and molecular line data to understand its nuclear structure.

Findings

Detection of water megamaser emission in 3C403

High-resolution imaging of the nuclear radio structure

Constraints on the distribution of molecular gas

Abstract

The standard unified scheme of active galactic nuclei requires the presence of high column densities of gas and dust potentially obscuring the central engine. So far, few direct subarcsecond resolution studies of this material have been performed toward radio galaxies. The goal of this paper is to elucidate the nuclear environment of the prototypical X-shaped Fanaroff-Riley type II radio galaxy 3C403, the only powerful radio galaxy known to host a water megamaser. Very Large Array A-array and single-dish Green Bank and Effelsberg 1.3 cm measurements were performed to locate and monitor the water maser emission. Very Long Baseline Interferometry 6 cm continuum observations were taken to analyze the spatial structure of the nuclear environment at even smaller scales, while the CO J=1-0 and 2-1 transitions were observed with the IRAM 30-m telescope to search for thermal emission from a spatially extended, moderately dense gas component.[abridged]