A Global 86GHz VLBI Survey of Compact Radio Sources

TL;DR

This paper reports a large-scale 86GHz VLBI survey of 127 compact radio sources, significantly expanding the database of high-frequency VLBI images, with detailed measurements of source structures and brightness temperatures.

Contribution

It provides the first extensive 86GHz VLBI imaging survey, increasing the number of accessible sources for future high-frequency imaging by a factor of 3-5.

Findings

Images for 109 sources were obtained, extending the database fivefold.

Most cores are resolved with brightness temperatures peaking at 10^11 K.

IDV sources have smaller sizes and higher brightness temperatures.

Abstract

We present results from a large 86GHz global VLBI survey of compact radio sources. The main goal of the survey is to increase by factors of 3--5 the total number of objects accessible for future 3-mm VLBI imaging. The survey observations reach the baseline sensitivity of 0.1Jy and image sensitivity of better than 10 mJy/beam. The total of 127 compact radio sources have been observed. The observations have yielded images for 109 sources, extending the database of the sources imaged at 86GHz with VLBI observation by a factor of 5, and only 6 sources have not been detected. The remaining 12 objects have been detected but could not be imaged due to insufficient closure phase information. Radio galaxies are less compact than quasars and BL Lacs on sub-milliarcsecond scale. Flux densities and sizes of core and jet components of all imaged sources have been estimated using Gaussian model fitting. From these measurements, brightness temperatures have been calculated, taking into account resolution limits of the data. The cores of 70% of the imaged sources are resolved. The core brightness temperatures of the sources peak at $\sim 10^{11}$ K and only 1% have brightness temperatures higher than $10^{12}$ K. Cores of Intraday Variable (IDV) sources are smaller in angular size than non-IDV sources, and so yield higher brightness temperatures.