The KCAL VERA 22 GHz calibrator survey

TL;DR

This paper presents a survey of 1536 radio sources at 22 GHz using VERA to identify suitable phase calibrators, revealing fewer compact sources at high frequencies compared to 8 GHz.

Contribution

It provides the first large-scale 22 GHz calibrator survey with detailed flux density measurements and detection statistics for high-frequency VLBI observations.

Findings

Half of the target sources were detected at 22 GHz.

The number of compact sources brighter than a given flux density at 22 GHz is half of that at 8 GHz.

The survey establishes a catalog of potential high-frequency phase calibrators.

Abstract

We observed at 22 GHz with the VLBI array VERA a sample of 1536 sources with correlated flux densities brighter than 200 mJy at 8 GHz. One half of target sources has been detected. The detection limit was around 200 mJy. We derived the correlated flux densities of 877 detected sources in three ranges of projected baseline lengths. The objective of these observations was to determine the suitability of given sources as phase calibrators for dual-beam and phase-referencing observations at high frequencies. Preliminary results indicate that the number of compact extragalactic sources at 22 GHz brighter than a given correlated flux density level is twice less than at 8 GHz.