Type: Talk
Session: Stellar Science and Crowded Fields
Author: Tom J. Wilson

Abstract: The Vera C. Rubin Observatory's LSST will, with its unparallelled completeness limit, frustrate current astronomical algorithms and computational pipelines. Chiefly, it will suffer unprecedented levels of crowding and confusion, which will result in a number of knock-on effects in the photometric catalogues that must be understood to fully exploit this rich dataset. In this talk I will discuss the astrometric problems that arise, since the positions and uncertainties from the LSST pipeline will not tell the whole story. For example, this will result, paradoxically, in both high false-positive and high false-negative counterpart association rates. I will describe a more general framework for handling the additional components of astrometric uncertainty, beyond the centroid precision that is provided by the data reduction pipeline, and detail how to model several key components of the extended Astrometric Uncertainty Function, such as those due to crowding, confusion, and blending as well as the effect of unmeasurable, unknown proper motions of objects only detected in the full-depth catalogue. Finally, I will touch upon the ramifications these astrometric uncertainties can have on the photometric measurements, with systematic effects on similar scales to typically-required precisions.