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The Korean Astronomical Society (한국천문학회)
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REEVALUATION OF KVN GAINS

  • Received : 2022.03.29
  • Accepted : 2022.04.25
  • Published : 2022.04.30
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Abstract

During the course of analysing both single-dish and very long baseline interferometry (VLBI) data obtained from the Korean VLBI Network (KVN), we found a systematic offset between flux density measurements from different antennas. We were able to attribute a majority of the systematic offsets to changes in the "a priori" antenna gains, which were found to have varied up to 10 percent at 22 GHz and up to 30 percent at 43 GHz. Using historical calibrator observations, we present a revised set of gains that may be applied to KVN data taken from 2015 August to 2019 January. Application of the revised gains to the KVN results in a consistency of correlated flux density measurements between the three baselines of approximately five percent. We found that images from the recalibrated data typically have a 50 percent higher dynamic range, with some cases showing an increase of dynamic range of up to a factor of three.

Keywords

Acknowledgement

We are grateful to the staff of the KVN who helped to operate the array and to correlate the data. The KVN and a high-performance computing cluster are facilities operated by the KASI (Korea Astronomy and Space Science Institute). The KVN observations and correlations are supported through the high-speed network connections among the KVN sites provided by the KREONET (Korea Research Environment Open NET-work), which is managed and operated by the KISTI (Korea Institute of Science and Technology Information). This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MIST) (2020R1A2C2009003). This research made use of Astropy (Astropy Collaboration et al., 2013, 2018), emcee (Foreman-Mackey et al., 2013), Matplotlib (Hunter, 2007), NumPy (Harris et al., 2020), and SciPy (Virtanen et al., 2020).

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