M2M modelling of the Galactic disc via PRIMAL: Fitting to Gaia Error Added Data

Abstract: We have adapted our made-to-measure (M2M) algorithm PRIMAL to use mock Milky Way like data constructed from an N-body barred galaxy with a boxy bulge in a known dark matter potential. We use M0 giant stars as tracers, with the expected error of the ESA space astrometry mission Gaia. We demonstrate the process of constructing mock Gaia data from an N-body model, including the conversion of a galactocentric Cartesian coordinate N-body model into equatorial coordinates and how to add error to it for a single stellar type. We then describe the modifications made to PRIMAL to work with observational error. This paper demonstrates that PRIMAL can recover the radial profiles of the surface density, radial velocity dispersion, vertical velocity dispersion and mean rotational velocity of the target disc, along with the pattern speed of the bar, to a reasonable degree of accuracy despite the lack of accurate target data. We also construct mock data which take into account dust extinction and show that PRIMAL recovers the structure and kinematics of the disc reasonably well. In other words, the expected accuracy of the Gaia data is good enough for PRIMAL to recover these global properties of the disc, at least in a simplified condition, as used in this paper.