An empirical model of the Gaia DR3 selection function

Understand

Interpreting and modelling astronomical catalogues requires an understanding of the catalogues' completeness or selection function: objects of what properties had a chance to end up in the catalogue.

• Here we set out to empirically quantify the completeness of the overall Gaia DR3 catalogue.
• This task is not straightforward because Gaia is the all-sky optical survey with the highest angular resolution to date and no consistent ``ground truth'' exists to allow direct comparisons.
• However, well-characterised deeper imaging enables an empirical assessment of Gaia's $G$-band completeness across parts of the sky.