Precise absolute astrometry from the VLBA imaging and polarimetry survey at 5 GHz

TL;DR

This paper provides highly accurate positions for 857 radio sources at 5 GHz using VLBA data, significantly improving astrometric precision and demonstrating effective ionospheric modeling with GPS data.

Contribution

It delivers the first precise astrometric positions for 430 sources at milliarcsecond accuracy from the VLBA survey at 5 GHz, with improved ionospheric correction methods.

Findings

Median position uncertainty of 0.5 mas

430 sources' positions determined for the first time

Ionospheric effects effectively modeled with GPS TEC maps

Abstract

We present in this paper accurate positions of 857 sources derived from the astrometric analysis of 16 eleven-hour experiments from the Very Long Baseline Array imaging and polarimetry survey at 5 GHz (VIPS). Among observed sources, positions of 430 objects were not determined before at a milliarcsecond level of accuracy. For 95% of the sources the uncertainty of their positions range from 0.3 to 0.9 mas, with the median value of 0.5 mas. This estimate of accuracy is substantiated by the comparison of positions of 386 sources that were previously observed in astrometric programs simultaneously at 2.3/8.6 GHz. Surprisingly, the ionosphere contribution to group delay was adequately modeled with the use of the total electron contents maps derived from GPS observations and only marginally affected estimates of source coordinates.