Action-based Dynamical Modelling for the Milky Way Disk

Abstract

We present RoadMapping, a full-likelihood dynamical modelling machinery that aims to recover the Milky Way's (MW) gravitational potential from large samples of stars in the Galactic disk. RoadMapping models the observed positions and velocities of stars with a parametrized, three-integral distribution function (DF) in a parametrized axisymmetric potential. We investigate through differential test cases with idealized mock data how the breakdown of model assumptions and data properties affect constraints on the potential and DF. Our key results are: (i) If the MW's true potential is not included in the assumed model potential family, we can - in the axisymmetric case - still find a robust estimate for the potential, with only <~ 10% difference in surface density within |z| <= 1.1 kpc inside the observed volume. (ii) Modest systematic differences between the true and model DF are inconsequential. E.g, when binning stars to define sub-populations with simple DFs, binning errors do not affect the modelling as long as the DF parameters of neighbouring bins differ by < 20%. In addition, RoadMapping ensures unbiased potential estimates for either (iii) small misjudgements of the spatial selection function (i.e., <~ 15% at the survey volume's edge), (iv) if distances are known to within 10%, or (v) if proper motion uncertainties are known within 10% or are smaller than delta mu <~ 1 mas/yr. Challenges are the rapidly increasing computational costs for large sample sizes. Overall, RoadMapping is well suited to making precise new measurements of the MW's potential with data from the upcoming Gaia releases.

23 pages, 19 figures, 3 tables, accepted for publication in ApJ

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Cited by in corpus (19)

• AGAMA: Action-based galaxy modelling architecture
• The mass of our Milky Way
• The Galactic Disc in Action Space as seen by Gaia DR2
• The vertical motion history of disk stars throughout the Galaxy
• Identifying resonances of the Galactic bar in Gaia DR2: I. Clues from action space
• Aurigaia: mock Gaia DR2 stellar catalogues from the Auriga cosmological simulations
• First Gaia dynamical model of the Milky Way disc with six phase space coordinates: a test for galaxy dynamics
• Galactic Rotation from Cepheids with Gaia DR2 and Effects of Non-Axisymmetry
• Action-based distribution function modelling for constraining the shape of the Galactic dark matter halo
• Unbiased TGAS$\times$LAMOST distances and the role of binarity
• Made-to-measure modeling of observed galaxy dynamics
• Deep Potential: Recovering the gravitational potential from a snapshot of phase space
• Self-consistent bulge/disk/halo galaxy dynamical modeling using integral field kinematics
• Action-based Dynamical Modeling for the Milky Way Disk: The Influence of Spiral Arms
• Quantifying the influence of bars on action-based dynamical modelling of disc galaxies
• Rediscovering the Milky Way with orbit superposition approach and APOGEE data I. Method validation
• The 3D Galactocentric velocities of Kepler stars: marginalizing over missing RVs
• Minimum-entropy constraints on galactic potentials
• GalPort: Investigation of the bar in action-angle space