Determination of the escape velocity of the Milky Way using a proper motion selected halo sample

Abstract

The {\it Gaia} mission has provided the largest catalogue ever of sources with tangential velocity information. However, using this catalogue for dynamical studies is difficult because most of the stars lack line-of-sight velocity measurements. Recently, we presented a selection of $\sim 10^7$ halo stars with accurate distances that have been selected based on their photometry and proper motions. Using this sample, we model the tail of the velocity distribution with a power-law distribution, a commonly used approach first established by \cite{Leonard1990THESPEED}. For the first time ever we use tangential velocities measured accurately for an unprecedented number of halo stars to estimate the escape velocity. In the solar neighbourhood, we obtain a very precise estimate of the escape velocity which is $497_{-8}^{+8}km/s$. This estimate is most likely biased low, our best guess is by 10\%. As a result, the true escape velocity most likely is closer to $550km/s$. The escape velocity directly constrains the total mass of the Milky Way. To find the best fitting halo mass and concentration parameter we adjusted the dark (spherical NFW) halo of a realistic Milky Way potential while keeping the circular velocity at the solar radius fixed at $v_c(R_{\odot })=232.8km/s$. The resulting halo parameters are $M_{200}^{+10\%}=1.11_{-0.07}^{+0.08}\cdot 10^{12}{\mathrm{M}}_{\odot }$ and concentration parameter $c^{+10\%}=11.8_{-0.3}^{+0.3}$, where we use the explicit notation to indicate that these have been corrected for the 10\% bias. The slope of the escape velocity with galactocentric distance is as expected in the inner Galaxy based on Milky Way models. Curiously, we find a disagreement beyond the solar radius which is likely an effect of a change in the shape of the velocity distribution and could be related to the presence of velocity clumps.

14 pages, 13 figures, accepted for publication in A&A

References in corpus (21)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• The NumPy array: a structure for efficient numerical computation
• The Gaia mission
• The EAGLE project: Simulating the evolution and assembly of galaxies and their environments
• galpy: A Python Library for Galactic Dynamics
• The mass distribution and gravitational potential of the Milky Way
• The Radial Velocity Experiment (RAVE): first data release
• The Milky Way's Circular Velocity Curve to 60 kpc and an Estimate of the Dark Matter Halo Mass from Kinematics of ~2400 SDSS Blue Horizontal Branch Stars
• The RAVE Survey: Constraining the Local Galactic Escape Speed
• The Radial Velocity Experiment (RAVE): Fifth Data Release
• Constraining the Galaxy's dark halo with RAVE stars
• Distances and parallax bias in Gaia DR2
• The local high velocity tail and the Galactic escape speed
• The mass of our Galaxy from satellite proper motions in the Gaia era
• Lessons from the curious case of the `fastest' star in Gaia DR2
• The Gaia DR2 parallax zero point: Hierarchical modeling of red clump stars
• The effects of dynamical substructure on Milky Way mass estimates from the high velocity tail of the local stellar halo
• New nearby hypervelocity stars and their spatial distribution from Gaia DR2
• The stellar kinematics of co-rotating spiral arms in Gaia mock observations
• A Lower Limit on the Mass of Our Galaxy from the H3 Survey
• The Reduced Proper Motion selected halo: methods and description of the catalogue

Cited by in corpus (19)

• The wide-field, multiplexed, spectroscopic facility WEAVE: Survey design, overview, and simulated implementation
• Milky Way Mass with K Giants and BHB Stars Using LAMOST, SDSS/SEGUE, and Gaia: 3D Spherical Jeans Equation and Tracer Mass Estimator
• Substructure at High Speed II: The Local Escape Velocity and Milky Way Mass with Gaia DR2
• Milky Way archaeology using RR Lyrae and type II Cepheids II. High velocity RR Lyrae stars, and mass of the Milky Way
• Unveiling the past evolution of the progenitor of the Helmi streams
• Constraints on the Galactic Centre environment from Gaia hypervelocity stars II: The evolved population
• The Escape Velocity Profile of the Milky Way from Gaia DR3
• Hidden deep in the halo: selection of a reduced proper motion halo catalogue and mining retrograde streams in the velocity space
• New stellar velocity substructures from Gaia DR3 proper motions
• Recommended conventions for reporting results from direct dark matter searches
• The Galactic Bulge exploration IV.: RR~Lyrae stars as traces of the Galactic bar -- 3D and 5D analysis, extinction variation
• On the chaos induced by the Galactic bar on the orbits of nearby halo stars
• Substructure at High Speed I: Inferring the Escape Velocity in the Presence of Kinematic Substructure
• The Inferred Abundance of Interstellar Objects of Technological Origin
• Indirect detection of dark matter absorption in the Galactic Center
• Discovery of a runaway star likely ejected by a Type Iax Supernova
• Milky Way Mass Through Escape Velocity Curve from LAMOST K Giants
• The disturbed outer Milky Way disc
• Life in the dark: Potential urability of moons of rogue planets