Characterisation of Long Baseline Calibrators at 2.3 GHz

TL;DR

This study evaluates 31 southern hemisphere radio sources for their effectiveness as calibrators at 2.3 GHz, finding most are suitable and nearly 90% are excellent calibrators for long baseline interferometry.

Contribution

It provides a detailed multi-epoch analysis of potential calibrators, classifying their suitability based on structure and variability at 2.3 GHz.

Findings

All sources are suitable interferometric calibrators.

Approximately 90% are classified as very good calibrators.

The study offers a classification framework for calibrator suitability.

Abstract

We present a detailed multi-epoch analysis of 31 potential southern hemisphere radio calibrators that were originally observed as part of a program to maintain the International Celestial Reference Frame (ICRF). At radio wavelengths, the primary calibrators are Active Galactic Nuclei (AGN), powerful radio emitters which exist at the centre of most galaxies. These are known to vary at all wavelengths at which they have been observed. By determining the amount of radio source structure and variability of these AGN, we determine their suitability as phase calibrators for long baseline radio interferometry at 2.3 GHz. For this purpose, we have used a set of complementary metrics to classify these 31 southern sources into five categories pertaining to their suitability as VLBI calibrators. We find that all of the sources in our sample would be good interferometric calibrators and almost ninety per cent would be very good calibrators.