Test of source selection for constructing a more stable and uniform celestial reference frame

TL;DR

This study evaluates and improves the stability of the celestial reference frame by selecting sources with minimal linear drift from VLBI data, resulting in two new source lists that enhance the ICRF2's stability and uniformity.

Contribution

The paper introduces a novel source selection method based on linear drift analysis, leading to two improved source lists for a more stable celestial reference frame.

Findings

Global rotation of axes is about twice better than ICRF2.

Two new source lists with 323 and 294 sources are proposed.

The improved selection enhances the stability and homogeneity of the celestial reference system.

Abstract

We aim to evaluate the possibility of improving the ICRS realization starting from the ICRF2 catalogue by investigating the coordinate time series of radio sources observed by VLBI between 1979 and 2016. Sources with long observational history are selected as the candidates and the least squares fits with special handling of the weights are performed to derive the linear drifts of the source coordinates. Then the sources are sorted based on the normalized linear drift (i) over the whole sky and (ii) in four homolographic areas divided by declinations. The axial stability of the reference system and sky distribution defined by the selected sources are evaluated, which are acted as the criterion for the final source lists. With our improved source selection scheme, two groups of sources are proposed and considered suitable for defining a more stable and homogeneous celestial reference system compared to the current ICRF2. The number of sources in the final lists are 323 and 294, respectively, and the global rotation of the axes derived from apparent motion of the sources are about two times better than the ICRF2.