Early science with Korean VLBI network: the QCAL-1 43GHz calibrator survey

TL;DR

This paper presents a VLBI survey at 43 GHz using the Korean VLBI Network, cataloging 637 sources including 623 newly observed at Q-band, evaluating the instrument's performance and identifying potential calibrator sources.

Contribution

The study provides the first VLBI observations at 43 GHz for many sources and assesses the performance of the new VLBI array in a high-frequency regime.

Findings

78% detection rate among observed sources

Detection limit ranges from 115 to 180 mJy depending on declination

33 sources detected for the first time in VLBI mode

Abstract

This paper presents the catalog of correlated flux densities in three ranges of baseline projection lengths of 637 sources from a 43 GHz (Q-band) survey observed with the Korean VLBI Network. Of them, 623 sources have not been observed before at Q-band with VLBI. The goal of this work in the early science phase of the new VLBI array is twofold: to evaluate the performance of the new instrument that operates in a frequency range of 22-129 GHz and to build a list of objects that can be used as targets and as calibrators. We have observed the list of 799 target sources with declinations down to -40 degrees. Among them, 724 were observed before with VLBI at 22 GHz and had correlated flux densities greater than 200 mJy. The overall detection rate is 78%. The detection limit, defined as the minimum flux density for a source to be detected with 90% probability in a single observation, was in a range of 115-180 mJy depending on declination. However, some sources as weak as 70 mJy have been detected. Of 623 detected sources, 33 objects are detected for the first time in VLBI mode. We determined their coordinates with the median formal uncertainty 20 mas. The results of this work set the basis for future efforts to build the complete flux-limited sample of extragalactic sources at frequencies 22 GHz and higher at 3/4 of the celestial sphere.