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

• Published in: Monthly notices of the Royal Astronomical Society Vol. 512; no. 2; pp. 1857 - 1884
• Main Authors: Sormani, Mattia C, Sanders, Jason L, Fritz, Tobias K, Smith, Leigh C, Gerhard, Ortwin, Schödel, Rainer, Magorrian, John, Neumayer, Nadine, Nogueras-Lara, Francisco, Feldmeier-Krause, Anja, Mastrobuono-Battisti, Alessandra, Schultheis, Mathias, Shahzamanian, Banafsheh, Vasiliev, Eugene, Klessen, Ralf S, Lucas, Philip, Minniti, Dante
• Format: Journal Article
• Language: English
• Published: Oxford University Press 01.05.2022; Oxford University Press (OUP): Policy P - Oxford Open Option A
• Subjects: Astronomi, astrofysik och kosmologi; Astronomy, Astrophysics and Cosmology; Fysik; Galaxy: centre; Galaxy: kinematics and dynamics; Galaxy: structure; Natural Sciences; Naturvetenskap; Physical Sciences; Sciences of the Universe; Galaxy: centre; Galaxy: structure; Galaxy: kinematics and dynamics; Astrophysics - Astrophysics of Galaxies
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stac639

Abstract The nuclear stellar disc (NSD) is a flattened high-density stellar structure that dominates the gravitational field of the Milky Way at Galactocentric radius $30\, {\rm pc}\lesssim R\lesssim 300\, {\rm pc}$. 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 $M_{\rm NSD} = 10.5^{+1.1}_{-1.0} \times 10^8 \, \, \rm M_\odot$, roughly exponential radial and vertical scale lengths of $R_{\rm disc} = 88.6^{+9.2}_{-6.9} \, {\rm pc}$ and $H_{\rm disc}=28.4^{+5.5}_{-5.5} \, {\rm pc}$, respectively, and a velocity dispersion $\sigma \simeq 70\, {\rm km\, s^{-1}}$ 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.