With the publication of Gaia DR2, 1.3 billion stars now have public parallax and proper motion measurements. In this contribution, we compare the results for sources that have both optical and radio measurements, focusing on circumstellar masers. For these large, variable and bright AGB stars, the VLBI astrometry results can be more robust. Moreover, there are a number of applications where VLBI astrometry provides unique data for studying stellar populations and Galactic structure. The BeSSel project not only provides parallax and proper motions at much larger distances than Gaia can reach, but it also uniquely samples the spiral arms of the Galaxy. The evolved stars in the BAaDE sample can potentially constrain the dynamics and stellar content of the inner bulge and bar of the Milky Way, not reachable in the optical.
@article{arxiv.1901.07804,
title = {The Synergy between VLBI and Gaia astrometry},
author = {Huib van Langevelde and Luis Henry Quiroga-Nuñez and Wouter Vlemmings and Laurent Loinard and Mareki Honma and Akiharu Nakagawa and Katharina Immer and Ross Burns and Ylva Pihlström and Lorant Sjouwerman and R. Michael Rich and Iniyan Natarajan and Roger Deane},
journal= {arXiv preprint arXiv:1901.07804},
year = {2019}
}
Comments
6 pages, accepted for the Proceedings of the 14th European VLBI Network Symposium & Users Meeting (typo in Authors' name, reference mixed up)