3D stellar kinematics at the Galactic center: measuring the nuclear star cluster spatial density profile, black hole mass, and distance

Abstract

We present 3D kinematic observations of stars within the central 0.5 pc of the Milky Way nuclear star cluster using adaptive optics imaging and spectroscopy from the Keck telescopes. Recent observations have shown that the cluster has a shallower surface density profile than expected for a dynamically relaxed cusp, leading to important implications for its formation and evolution. However, the true three dimensional profile of the cluster is unknown due to the difficulty in de-projecting the stellar number counts. Here, we use spherical Jeans modeling of individual proper motions and radial velocities to constrain for the first time, the de-projected spatial density profile, cluster velocity anisotropy, black hole mass ($M_{\mathrm{BH}}$), and distance to the Galactic center ($R_0$) simultaneously. We find that the inner stellar density profile of the late-type stars, $\rho (r)\propto r^{-\gamma }$ to have a power law slope $\gamma =0.05_{-0.60}^{+0.29}$, much more shallow than the frequently assumed Bahcall $\&$ Wolf slope of $\gamma =7/4$. The measured slope will significantly affect dynamical predictions involving the cluster, such as the dynamical friction time scale. The cluster core must be larger than 0.5 pc, which disfavors some scenarios for its origin. Our measurement of $M_{\mathrm{BH}}=5.76_{-1.26}^{+1.76}\times 10^6$ $M_{\odot }$ and $R_0=8.92_{-0.55}^{+0.58}$ kpc is consistent with that derived from stellar orbits within 1${}^{\prime \prime }$ of Sgr A*. When combined with the orbit of S0-2, the uncertainty on $R_0$ is reduced by 30% ($8.46_{-0.38}^{+0.42}$ kpc). We suggest that the MW NSC can be used in the future in combination with stellar orbits to significantly improve constraints on $R_0$.

7 pages, 3 figures, 2 tables, ApJL accepted

References in corpus (26)

• MultiNest: an efficient and robust Bayesian inference tool for cosmology and particle physics
• Monitoring stellar orbits around the Massive Black Hole in the Galactic Center
• Measuring Distance and Properties of the Milky Way's Central Supermassive Black Hole with Stellar Orbits
• The Galactic Center Massive Black Hole and Nuclear Star Cluster
• High Proper Motion Stars in the Vicinity of Sgr A*: Evidence for a Supermassive Black Hole at the Center of Our Galaxy
• The Infrared Telescope Facility (IRTF) Spectral Library: Cool Stars
• Stellar Dynamics in the Galactic centre: Proper Motions and Anisotropy
• A Disk of Young Stars at the Galactic Center as Determined by Individual Stellar Orbits
• Long Term Evolution of Massive Black Hole Binaries
• The nuclear star cluster of the Milky Way: proper motions and mass
• The structure of the nuclear stellar cluster of the Milky Way
• Improving Galactic Center Astrometry by Reducing the Effects of Geometric Distortion
• Dissipationless Formation and Evolution of the Milky Way Nuclear Star Cluster
• High angular resolution integral-field spectroscopy of the Galaxy's nuclear cluster: a missing stellar cusp?
• Two measures of the shape of the Milky Way's dark halo
• The Distribution of Stars and Stellar Remnants at the Galactic Center
• Kinematics of the old stellar population at the Galactic Center
• Stellar Populations in the Central 0.5 pc of the Galaxy I: A New Method for Constructing Luminosity Functions and Surface-Density Profiles
• A Complete Spectroscopic Survey of the Milky Way satellite Segue 1: Dark matter content, stellar membership and binary properties from a Bayesian analysis
• Red giant stellar collisions in the Galactic Centre
• Secular Stellar Dynamics near a Massive Black Hole
• A Cusp Slope -- Central Anisotropy Theorem
• The stars of the galactic center
• A Non-Parametric Estimate of the Mass of the Central Black Hole in the Galaxy
• Deriving the mass distribution of M87 from globular clusters
• Ejection of Hyper-Velocity Stars from the Galactic Centre by Intermediate-Mass Black Holes

Cited by in corpus (63)

• Trigonometric Parallaxes of High Mass Star Forming Regions: the Structure and Kinematics of the Milky Way
• First Sagittarius A* Event Horizon Telescope Results. VI: Testing the Black Hole Metric
• Testing General Relativity with stellar orbits around the supermassive black hole in our Galactic center
• Black hole shadow in an asymptotically-flat, stationary, and axisymmetric spacetime: The Kerr-Newman and rotating regular black holes
• The old nuclear star cluster in the Milky Way: dynamics, mass, statistical parallax, and black hole mass
• Globular Cluster Streams as Galactic High-Precision Scales - The Poster Child Palomar 5
• Testing General Relativity with the Shadow Size of Sgr A*
• On the charge of the Galactic centre black hole
• Large scale kinematics and dynamical modelling of the Milky Way nuclear star cluster
• MMT Hypervelocity Star Survey III: A Complete Survey of Faint B-type Stars in the Northern Milky Way Halo
• Sgr A* and General Relativity
• The Milky Way's Supermassive Black Hole: How good a case is it? A Challenge for Astrophysics & Philosophy of Science
• The nuclear cluster of the Milky Way: Our primary testbed for the interaction of a dense star cluster with a massive black hole
• Testing the No-Hair Theorem with Observations of Black Holes in the Electromagnetic Spectrum
• The Nuclear Cluster of the Milky Way: Total Mass and Luminosity (long version)
• On the distribution of stellar remnants around massive black holes: slow mass segregation, star cluster inspirals and correlated orbits
• Testing General Relativity with Accretion-Flow Imaging of Sgr A*
• Proper motions and kinematics of selected bulge globular clusters
• Dynamical friction in cuspy galaxies
• Recent advances in the determination of some Galactic constants in the Milky Way
• Clustering of Local Group distances: publication bias or correlated measurements? IV. The Galactic Center
• Formation and evolution of nuclear star clusters with in-situ star-formation: Nuclear cores and age segregation
• Mapping the Outer Edge of the Young Stellar Cluster in the Galactic Center
• Median Statistics Estimate of the Distance to the Galactic Center
• Testing alternative theories of gravity by fitting the hot-spot data of Sgr A*
• Effect of Electromagnetic Interaction on Galactic Center Flare Components
• Gravitational-Wave Signatures from Compact Object Binaries in the Galactic Center
• Unbound Debris Streams and Remnants Resulting From the Tidal Disruptions of Stars by Supermassive Black Holes
• The Post-Periapse Evolution of Galactic Center Source G1: The second case of a resolved tidal interaction with a supermassive black hole
• A black hole window into p-wave dark matter annihilation
• Confusing binaries: the role of stellar binaries in biasing disk properties in the Galactic Center
• Search for gamma-ray emission from $p$-wave dark matter annihilation in the Galactic Center
• On Socially Distant Neighbors: Using Binaries to Constrain the Density of Objects in the Galactic Center
• On the origin of the B-stars in the Galactic center
• Does the Milky Way Obey Spiral Galaxy Scaling Relations?
• On the neutral gas content of nine new Milky Way satellite galaxy candidates
• Characterizing and Improving the Data Reduction Pipeline for the Keck OSIRIS Integral Field Spectrograph
• An Adaptive Optics Survey of Stellar Variability at the Galactic Center
• Search for Surviving Companions of Progenitors of Young LMC Type Ia Supernova Remnants
• On the Rotation Speed of the Milky Way Determined from HI Emission
• On the Newtonian and Spin-induced Perturbations felt by the Stars Orbiting around the Massive Black Hole in the Galactic Center
• Proper motion survey and kinematic analysis of the Rho Ophiuchi embedded cluster
• Gravitational Encounters and the Evolution of Galactic Nuclei. IV. Captures Mediated by Gravitational-Wave Energy Loss
• The influence of the secular perturbation of an intermediate-mass companion: I. Eccentricity excitation of disk stars at the Galactic center
• Systematic uncertainties from halo asphericity in dark matter searches
• Enhanced Line Signals from Annihilating Kaluza-Klein Dark Matter
• A Slowly Precessing Disk in the Nucleus of M31 as the Feeding Mechanism for a Central Starburst
• The fate of supernova remnants near quiescent supermassive black holes
• The Role of Nuclear Star Clusters in Enhancing Supermassive Black Hole Feeding Rates During Galaxy Mergers
• Geometric Aspects and Testing of the Galactic Center Distance Determination from Spiral Arm Segments
• Magnetic fields near the peripheries of galactic discs
• Orbit-superposition models of discrete, incomplete stellar kinematics: application to the Galactic centre
• Faint Dark Matter Annihilation Signals and the Milky Way's Supermassive Black Hole
• The influence of the secular perturbation of an intermediate-mass companion: II. Ejection of hypervelocity stars from the Galactic Center
• Binary Natal Kicks in the Galactic Center: X-ray Binaries, Hypervelocity Stars, and Gravitational Waves
• Dynamical mass distribution and velocity structure of the Galactic centre
• Probing the formation of planetesimals in the Galactic Centre using Sgr A* flares
• Double progenitor origin of the S-star cluster
• The contribution of young core-collapse supernova remnants to the X-ray emission near quiescent supermassive black holes
• Observational constraints on the formation and evolution of the Milky Way nuclear star cluster with Keck and Gemini
• Analytic Post-Newtonian Astrometric and Spectroscopic Models of Orbits around Black Holes
• The Milky Way's nuclear star cluster and massive black hole
• Star-formation in nuclear clusters and the origin of the Galactic Center apparent core distribution