2020/11/20 by Mark A. Fardal, Roeland van der Marel, Andres del Pino +2 · 9 citations
Physics and Astronomy · Social Sciences · #Astrometry #Astronomy and Astrophysical Research #Educational Leadership and Practices #Milky Way #Parallax #Population #Proper motion #Sky #Stars #Stellar, planetary, and galactic studies #Systematic error #astro-ph.GA #astro-ph.IM
paper · pdf · doi:10.3847/1538-3881/abcccf
published in The Astronomical Journal 161(2), 58 (Institute of Physics) · Accepted in AJ. 17 pages, 11 figures. Higher resolution figures available in journal. Eagerly anticipating Gaia EDR3
arxiv created 2020/11/20 · openalex created_date 2020/12/07 · openalex publication_date 2021/01/11 · arxiv updated 2021/01/20 · openalex updated_date 2026/08/06
Abstract Parallaxes measured by the Gaia mission have huge significance for astronomy, but parallaxes in Gaia DR2 are known to have systematic errors that depend on the source position and other quantities. We use the abundant information in faint Milky Way stars, along with the Gaia Object Generator simulation of the Gaia catalog, to probe the spatial dependence of Gaia DR2 parallax systematic errors in an empirical way. The parallax signal, concentrated in thick disk turnoff stars with magnitude G ∼ 17, is sufficient to construct maps of the parallax systematic error over the majority of the sky. These maps show a locally regular “waffle pattern” on ∼1° scales following Gaia scan directions, stronger linear “scar” features, and coherent variations on larger scales. The parallax bias maps also retain traces of astrophysical effects such as dust clouds. The waffle pattern, known from earlier maps of the Magellanic Clouds, extends over the entire sky; its local rms amplitude averages 15 μ as and varies by about a factor of two. The strength of this pattern increases by a factor ∼6 from magnitude G = 13 to G = 20. Correlations with parallaxes of quasars and of stars with independent distance estimates support our bias estimates. Using similar methods, we map systematic errors in the proper motion and examine the relationship with the parallax systematics. We provide a code package to access and query our bias maps. Similar tests on the general stellar population should be useful in quantifying systematic errors in future Gaia releases.