GA ; Instrumentation and Methods for Astrophysics astro-ph. IM ; Solar and Stellar Astrophysics astro-ph.
SR Gaia DR2 published positions, parallaxes and proper motions for an unprecedented 1, sources, revolutionising the field of Galactic dynamics. We complement this data with the Astrometry Spread Function ASFthe expected uncertainty in the measured positions, proper motions and parallax for a non-accelerating point source.
The ASF is a Gaussian function for which we construct the 5D astrometric covariance matrix as a function of position on the sky and apparent magnitude using the Gaia DR2 scanning law and demonstrate excellent agreement with the observed data.
The ASF will enable characterisation of binary systems, exoplanet orbits, astrometric microlensing events and extended sources which add an excess astrometric noise to the expected astrometry uncertainty. IM ; Astrophysics of Galaxies astro-ph. III stars, as of yet, have not been detected, however as we move into the era of extremely large telescopes this is likely to change.
One likely tracer for Pop. III stars and radiative transfer i.
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Furthermore, we find that should Pop.