Who is In, and Who is Not? Determining the Gaia Survey Selection Function

The European Space Agency's Gaia mission is the most successful European space mission as measured by the rate of publications appearing that use Gaia's data. The astrometric, photometric, and radial velocity catalogs provided through the second Gaia data release in April 2018 are the standard in fundamental astronomical data, with much more and much richer data appearing in future Gaia data releases. However the full transformative potential of the Gaia mission is currently not being realized because we lack a detailed description of the survey selection function; the information needed to correctly account for data missing from the Gaia catalog. Without the selection function is is impossible to extrapolate from statements about objects populations in a catalog into insights in fundamental physics and astrophysics.

It is the objective of this proposal to research, develop, and implement the Gaia selection function, as well selection functions for Gaia combined with other surveys. We will make available publicly the data products and open source computer applications needed by scientists to apply the selection functions to their analyses of the Gaia data. This will give a dramatic boost to the scientific exploitation of the data form this flagship European space mission, leading to higher quality science, more publications, and better reproducibility of the results. The Gaia survey data will set the standard in fundamental astronomical data for decades to come and the efforts proposed here will contribute to a much increased legacy value of this space mission.