Influence of the Galactic Gravitational Field on the Positional Accuracy of Extragalactic Sources. II. Observational Appearances and Detectability

Abstract

Abstract We consider the possibility of detecting the jitter effect of apparent celestial positions of distant sources due to local fluctuations of the Galaxy gravitational field. The observation of two samples of extragalactic sources (target and control) in different sky directions using the high-precision radio interferometry is proposed. It is shown that on a scale of ∼2 yr, it is possible to detect a systematic increase in the standard deviation of measured arc lengths of pairs of target sources compared to the control ones at the 3σ level if the accuracy of differential astrometric observations is around 10 μas. For the current state-of-the-art accuracy of 30 μas achieved at the KVN or VERA interferometers, which have shorter baselines in comparison with very long baseline interferometry, the target and control samples will differ only at the 2σ level on the scale of 10 yr. To achieve the 3σ level on this time interval, it is necessary to improve the accuracy up to ∼20 μas. Other possible effects that can also affect the arc length measurements between two sources are discussed, and an observational strategy to minimize them is suggested.