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.
Bibliographical noteFunding Information:
We thank the anonymous referee for the useful comments that helped to improve the manuscript. We are grateful to all staff at the KVN who helped to operate the array and to correlate the data. The KVN is a facility operated by the Korea Astronomy and Space Science Institute. This paper is a result of the collaborative project between Korea Astronomy and Space Science Institute and Yonsei University through DRC program of Korea Research Council of Fundamental Science and Technology (DRC-12-2-KASI). This work has been also supported by the SRC program of the National Research Foundation of Korea and Science Fellowship of POSCO TJ Park Foundation.
All Science Journal Classification (ASJC) codes
- Aerospace Engineering
- Astronomy and Astrophysics
- Atmospheric Science
- Space and Planetary Science
- Earth and Planetary Sciences(all)