Demonstration of KVN phase referencing capability

TL;DR

This paper demonstrates the successful application of the KVN phase referencing technique in VLBI observations to detect weak AGN cores in the Virgo cluster, showcasing improved high-frequency imaging capabilities.

Contribution

It presents the first demonstration of KVN phase referencing at high frequency, enabling detection of weak AGNs in the Virgo cluster with improved calibration methods.

Findings

Successful detection of weak AGN cores using phase referencing.

Comparison of phase referencing with self-calibration techniques.

High-resolution radio maps of Virgo cluster galaxies at 22 GHz.

Abstract

We present the results of Very Long Baseline Interferometry (VLBI) observations using the phase reference technique to detect weak Active Galactic Nuclei (AGN) cores in the Virgo cluster. Our observations were carried out using the Korean VLBI Network (KVN). We have selected eight representative radio galaxies, seven Virgo cluster members and one galaxy (NGC 4261) that is likely to be in the background. The selected galaxies are located in a range of density regions showing various morphology in 1.4 GHz continuum. Since half of our targets are too weak to be detected at K-band we applied a phase referencing technique to extend the source integration time by calibrating atmospheric phase fluctuations. We discuss the results of the phase referencing method at high frequency observations and we compare them with self-calibration on the relatively bright AGNs, such as M87, M84 and NGC 4261. In this manuscript we present the radio intensity maps at 22 GHz of the Virgo cluster sample while we demonstrate for first time the capability of KVN phase referencing technique.