Self-consistent modelling of the Milky Way’s nuclear stellar disc

The nuclear stellar disc (NSD) is a flattened high-density stellar structure that dominates the gravitational field of the Milky Way at Galactocentric radius 30pc≲R≲300pc⁠. We construct axisymmetric self-consistent equilibrium dynamical models of the NSD in which the distribution function is an analytic function of the action variables. We fit the models to the normalized kinematic distributions (line-of-sight velocities + VIRAC2 proper motions) of stars in the NSD survey of Fritz et al., taking the foreground contamination due to the Galactic Bar explicitly into account using an N-body model. The posterior marginalized probability distributions give a total mass of MNSD=10.5+1.1−1.0×108M⊙⁠, roughly exponential radial and vertical scale lengths of Rdisc=88.6+9.2−6.9pc and Hdisc=28.4+5.5−5.5pc⁠, respectively, and a velocity dispersion σ≃70kms−1 that decreases with radius. We find that the assumption that the NSD is axisymmetric provides a good representation of the data. We quantify contamination from the Galactic Bar in the sample, which is substantial in most observed fields. Our models provide the full 6D (position + velocity) distribution function of the NSD, which can be used to generate predictions for future surveys. We make the models publicly available as part of the software package AGAMA. © 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.MCS acknowledges financial support from the European Research Council via the ERC Synergy Grant ‘ECOGAL – Understanding our Galactic ecosystem: from the disk of the Milky Way to the formation sites of stars and planets’ (grant 855130). JLS thanks the support of the Royal Society (URF\R1\191555). EV acknowledges support from STFC via the consolidated grant to the Institute of Astronomy. DM acknowledges support from project CATA FB210003. AMB acknowledges funding from the EU Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 895174. JM acknowledges support from the UK Science and Technology Facilities Council under grant number ST/S000488/I. MCS, NN, FN-L, and RSK gratefully acknowledge support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) - Project-ID 138713538 - SFB 881 (‘The Milky Way System’, subprojects B1, B2, B8). FN-L acknowledges the sponsorship provided by the Federal Ministry for Education and Research of Germany through the Alexander von Humboldt Foundation. RS and BS acknowledge financial support from the State Agency for Research of the Spanish MCIU through the ‘Center of Excellence Severo Ochoa’ award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709) and financial support from national project PGC2018-095049-B-C21 (MCIU/AEI/FEDER, UE). RSK acknowledges support from the Heidelberg cluster of excellence EXC 2181 (Project-ID 390900948) ‘STRUCTURES: A unifying approach to emergent phenomena in the physical world, mathematics, and complex data’ funded by the German Excellence Strategy. This work used computing resources provided by the state of Baden-Württemberg through bwHPC and the German Research Foundation (DFG) through grant INST 35/1134-1 FUGG. Data are stored at SDS@hd supported by the Ministry of Science, Research and the Arts Baden-Württemberg (MWK) and DFG through grant INST 35/1314-1 FUGG.Peer reviewe