Globular clusters with Gaia

Bellazzini, M.M.BellazziniGiuffrida, G.G.GiuffridaPancino, ElenaElenaPancinoMarinoni, S.S.Marinoni2020-09-172020-09-172017-01-01https://hdl.handle.net/20.500.13025/5320Monthly Notices of the Royal Astronomical Society, Advance AccessThe treatment of crowded fields in Gaia data will only be a reality in a few years from now. In particular, for globular clusters, only the end-of-mission data (public in 2022-2023) will have the necessary full crowding treatment and will reach sufficient quality for the faintest stars. As a consequence, the work on the deblending and decontamination pipelines is still ongoing. We describe the present status of the pipelines for different Gaia instruments, and we model the end-of-mission crowding errors on the basis of available information. We then apply the nominal post-launch Gaia performances, appropriately worsened by the estimated crowding errors, to a set of 18 simulated globular clusters with different concentration, distance, and field contamination. We conclude that there will be 103-104 stars with astrometric performances virtually untouched by crowding (contaminated by <1 mmag) in the majoritiy of clusters. The most limiting factor will be field crowding, not cluster crowding the most contaminated clusters will only contain 10-100 clean stars. We also conclude that (i) the systemic proper motions and parallaxes will be determined to 1% or better up to ~=15 kpc, and the nearby clusters will have radial velocities to a few km s-1 ; (ii) internal kinematics will be of unprecendented quality, cluster masses will be determined to ~=10% up to 15 kpc and beyond, and it will be possible to identify differences of a few km s-1 or less in the kinematics (if any) of cluster sub-populations up to 10 kpc and beyond; (iii) the brightest stars (V~=17 mag) will have space-quality, wide-field photometry (mmag errors), and all Gaia photometry will have 1-3% errors on the absolute photometric calibration.astrometryparallaxesglobular clusters generalGlobular clusters with Gaia10.1093/mnras/stx079http://adsabs.harvard.edu/abs/2017MNRAS.tmp...88P2017MNRAS.tmp...88P