A Deep View into the Nucleus of the Sagittarius Dwarf Spheroidal Galaxy with MUSE. III. Discrete multi-component population-dynamical models based on the Jeans equations

Abstract

We present comprehensive multi-component dynamical models of M54 (NGC6715), the nuclear star cluster of the Sagittarius dwarf galaxy (Sgr), which is undergoing a tidal disruption in the Milky Way halo. Previous papers in the series used a large MUSE mosaic data set to identify multiple stellar populations in the system and study their kinematic differences. Here we use Jeans-based dynamical models that fit the population properties (mean age and metallicity), spatial distributions, and kinematics simultaneously. They provide a solid physical explanation to our previous findings. The population-dynamical models deliver a comprehensive view of the whole system, and allow us to disentangle the different stellar populations. We explore their dynamical interplay and confirm our previous findings about the build-up of Sgr's nuclear cluster via contributions from globular cluster stars, Sgr inner field stars, and in-situ star formation. We explore various parameterisations of the gravitational potential and show the importance of a radially varying mass-to-light ratio for the proper treatment of the mass profile. We find a total dynamical mass within M54's tidal radius ($\sim 75$ pc) of $1.60\pm 0.07\times 10^6$ Msun in excellent agreement with $N$-body simulations. The metal-poor globular cluster stars contribute about $65\%$ of the total mass or $1.04\pm 0.05\times 10^6$ Msun. The metal-rich stars can be further divided into young and intermediate age populations that contribute $0.32\pm 0.02\times 10^6$ Msun ($20\%$) and $0.24\pm 0.02\times 10^6$ Msun ($15\%$), respectively. Our population-dynamical models successfully distinguish the different stellar populations in Sgr's nucleus because of their different spatial distributions, ages, metallicities, and kinematic features.

Accepted for publication in ApJ

References in corpus (26)

• The Dartmouth Stellar Evolution Database
• The ACS Survey of Galactic Globular Clusters. I. Overview and Clusters Without Previous HST Photometry
• Measuring the inclination and mass-to-light ratio of axisymmetric galaxies via anisotropic Jeans models of stellar kinematics
• Gaia EDR3 view on Galactic globular clusters
• The nucleus of the Sagittarius dSph galaxy and M54: a window on the process of galaxy nucleation
• The ACS Survey of Galactic Globular Clusters: M54 and Young Populations in the Sagittarius Dwarf Spheroidal Galaxy
• The Coincidence of Nuclear Star Clusters and Active Galactic Nuclei
• N-body modeling of globular clusters: Masses, mass-to-light ratios and intermediate-mass black holes
• Improved Dynamical Constraints on the Masses of the Central Black Holes in Nearby Low-mass Early-type Galactic Nuclei And the First Black Hole Determination for NGC 205
• Surface Brightness Profiles of Galactic Globular Clusters from Hubble Space Telescope Images
• The HST/ACS Coma Cluster Survey. X. Nuclear star clusters in low-mass early-type galaxies: scaling relations
• A large stellar evolution database for population synthesis studies. IV. Integrated properties and spectra
• Density and kinematic cusps in M54 at the heart of the Sagittarius dwarf galaxy: evidence for a 10^4 M_sun Black Hole?
• Self-consistent simulations of Nuclear Cluster formation through Globular Cluster orbital decay and merging
• Merging of globular clusters within inner galactic regions. II. The Nuclear Star Cluster formation
• The Accreted Nuclear Clusters of the Milky Way
• A deep view into the nucleus of the Sagittarius Dwarf Spheroidal Galaxy with MUSE. I. Data and stellar population characterization
• A discrete chemo-dynamical model of the dwarf spheroidal galaxy Sculptor: mass profile, velocity anisotropy and internal rotation
• Diversity of nuclear star cluster formation mechanisms revealed by their star formation histories
• Self-Regulated Fueling of Galaxy Centers: Evidence for Star-Formation Feedback in IC342's Nucleus
• Pericentric passage-driven star formation in satellite galaxies and their hosts: CLUES from Local Group simulations
• Disentangling the formation mechanisms of nuclear star clusters
• Characterization of the velocity anisotropy of accreted globular clusters
• Dynamical modelling of globular clusters: challenges for the robust determination of IMBH candidates
• The peculiar kinematics of the multiple populations in the globular cluster Messier 80 (NGC 6093)
• Spatially Resolving the Star Formation Histories of Three Nearby Nuclear Star Clusters

Cited by in corpus (13)

• Evidence for a bottom-light initial mass function in massive star clusters
• oMEGACat I: MUSE spectroscopy of 300,000 stars within the half-light radius of $\omega$ Centauri
• oMEGACat III. Multi-band photometry and metallicities reveal spatially well-mixed populations within $\omega$ Centauri's half-light radius
• oMEGACat II -- Photometry and proper motions for 1.4 million stars in Omega Centauri and its rotation in the plane of the sky
• An elusive dark central mass in the globular cluster M4
• Abundance ties: Nephele and the globular cluster population accreted with $\omega$ Cen. Based on APOGEE DR17 and Gaia EDR3
• Equilibrium dynamical models in the inner region of the Large Magellanic Cloud based on Gaia DR3 kinematics
• oMEGACat. VI. Analysis of the overall kinematics of Omega Centauri in 3D: velocity dispersion, kinematic distance, anisotropy, and energy equipartition
• The Pristine Inner Galaxy Survey (PIGS) X. Probing the early chemical evolution of the Sagittarius dwarf galaxy with carbon abundances
• Dynamical mass distribution and velocity structure of the Galactic centre
• Kinematics of metallicity populations in Omega Centauri using Gaia Focused Product Release and Hubble Space Telescope
• Chemical tagging with APOGEE, MUSE, and HST: constraints on the formation of $\omega$ Centauri
• Dwarf galaxies in the MATLAS Survey: Hubble Space Telescope observations of nuclear star clusters