Milky Way Mass Through Escape Velocity Curve from LAMOST K Giants

Abstract

Escape velocity has long been used to constrain the mass of the Dark Matter (DM) halo in the Milky Way (MW). Here we present a study of the escape velocity curve using a sample of high-velocity K giants with full 6D phase-space information and relatively good quality, selected from LAMOST DR8 and cross-matched with Gaia DR3. To expand the high-velocity stars to larger distances, we used radius-dependent criteria of total velocity, that is, $v_{\mathrm{GC}}>300\mathrm{km}{\mathrm{s}}^{-1}$ for the solar neighborhood; $v_{\mathrm{GC}}>v_{\min }\sim 0.6\times v_{\mathrm{esc}}(r_{\mathrm{GC}})$ for outer region. We also selected halo stars based on $v_{\varphi }-[Fe/H]$ information to ensure that the sample is isotropic. We modeled the velocity distribution with traditional power-law models to determine the escape velocity in each radial bin. For the first time, we have directly measured a relatively continuous escape velocity curve that can extend to Galactocentric radii of $\sim 50$ kpc, finding a decline in agreement with previous studies. The escape velocity at the solar position yielded by our measurements is $523.74_{-13.47}^{+12.83}\mathrm{km}{\mathrm{s}}^{-1}$. Combined with the local circular velocity, we estimated the mass of the MW assuming a Navarro-Frenk-White DM profile, which resulted in a total mass of $M_{200,\mathrm{total}}=0.90_{-0.07}^{+0.06}\times 10^{12}{M}_{\odot }$, with a concentration of $c_{200}=13.47_{-1.70}^{+1.85}$. The small uncertainty implies that including the escape velocities beyond the solar neighborhood can result in a more precise mass estimate. Our derived MW mass is consistent with some recent studies using the escape velocity as well as other tracers, which may support a lower mass of the DM halo than in the past.

13 pages, 8 figures, published in ApJ

References in corpus (28)

• Array Programming with NumPy
• The Gaia mission
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• Gaia Data Release 3: Summary of the content and survey properties
• galpy: A Python Library for Galactic Dynamics
• The Radial Velocity Experiment (RAVE): first data release
• The GALAH Survey: Scientific Motivation
• The RAVE Survey: Constraining the Local Galactic Escape Speed
• Search for dark matter annihilations towards the inner Galactic halo from 10 years of observations with H.E.S.S
• "Skinny Milky Way, Please", says Sagittarius
• The local high velocity tail and the Galactic escape speed
• $S^5$: Probing the Milky Way and Magellanic Clouds potentials with the 6-D map of the Orphan-Chenab stream
• Detection of the Keplerian decline in the Milky Way rotation curve
• The K giant stars from the LAMOST survey data I: identification, metallicity, and distance
• The Circular Velocity Curve of the Milky Way from 5 to 25 kpc using luminous red giant branch star
• Mapping the Milky Way Disk with Gaia DR3: 3D extended kinematic maps and rotation curve to $\approx 30$ kpc
• A Milky Way with a massive, centrally concentrated thick disc: new Galactic mass models for orbit computations
• The effects of dynamical substructure on Milky Way mass estimates from the high velocity tail of the local stellar halo
• Milky Way total Mass derived by Rotation Curve and Globular Cluster kinematics from Gaia EDR3
• 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
• Classifying globular clusters and applying them to estimate the mass of the Milky Way
• On the origins of extreme velocity stars as revealed by large-scale Galactic surveys
• The Local Group's mass: probably no more than the sum of its parts
• The Escape Velocity Profile of the Milky Way from Gaia DR3
• A Catalog of Distance Determinations for the LAMOST DR8 K Giants in the Galactic Halo
• Substructure at High Speed I: Inferring the Escape Velocity in the Presence of Kinematic Substructure