The Photo-Astrometric vertical tracer density of the Milky Way – I. The method

ABSTRACT We introduce a method to infer the vertical distribution of stars in Milky Way using Poisson likelihood function, with view applying our Gaia catalogue. show how account for sample selection function and parallax measurement uncertainties. Our is validated against simulated drawn from model two exponential discs power-law halo profile. A mock generated astrometry whilst realistic uncertainties are Astrometric Spread Function. The fit order rediscover input parameters used generate sample. recover posterior distributions that accurately within statistical uncertainties, demonstrating efficacy method. Using GUMS synthetic catalogue, we find parameter fits can be heavily biased by overly simplistic model; however, thin thick not significantly impacted. apply this Early Data Release 3 companion paper where also quantify systematic introduced oversimplifications model.