Axisymmetric Schwarzschild models of an isothermal axisymmetric mock dwarf spheroidal galaxy

Abstract

We test the ability of Schwarzschild's orbit superposition method in measuring the mass content, scale radius and shape of a flattened dwarf spheroidal galaxy. Until now, most dynamical model efforts have assumed that dwarf spheroidal galaxies and their host halos are spherical. We use an Evans model (1993) to construct an isothermal mock galaxy whose properties somewhat resemble those of the Sculptor dwarf spheroidal galaxy. This mock galaxy contains flattened luminous and dark matter components, resulting in a logarithmic profile for the global potential. We have tested how well our Schwarzschild method could constrain the characteristic parameters of the system for different sample sizes, and also if the functional form of the potential was unknown. When assuming the true functional form of the potential, the Schwarzschild modelling technique is able to provide an accurate and precise measurement of the characteristic mass parameter of the system and reproduces well the light distribution and the stellar kinematics of our mock galaxy. When assuming a different functional form for the potential, such as a flattened NFW profile, we also constrain the mass and scale radius to their expected values. However in both cases, we find that the flattening parameter remains largely unconstrained. This is likely because the information content of the velocity dispersion on the geometric shape of the potential is too small, since $\sigma$ is constant across our mock dSph. Our results using Schwarzschild's method indicate that the mass enclosed can be derived reliably, even if the flattening parameter is unknown, and already for samples containing 2000 line-of-sight radial velocities, such as those currently available. Further applications of the method to more general distribution functions of flattened systems are needed to establish how well the flattening of dSph dark halos can be determined.

arXiv comment13 pages, 14 figures. Comments are welcome

References in corpus (39)

• The Structure of Cold Dark Matter Halos
• Dark Matter Substructure in Galactic Halos
• Where are the missing galactic satellites?
• Dwarf Galaxies of the Local Group
• The observed properties of dwarf galaxies in and around the Local Group
• Too big to fail? The puzzling darkness of massive Milky Way subhaloes
• Triaxial Modeling of Halo Density Profiles with High-resolution N-body Simulations
• Accurate masses for dispersion-supported galaxies
• A Universal Mass Profile for Dwarf Spheroidal Galaxies?
• Reconciling dwarf galaxies with LCDM cosmology: Simulating a realistic population of satellites around a Milky Way-mass galaxy
• Baryons Matter: Why Luminous Satellite Galaxies Have Reduced Central Masses
• The kinematic status and mass content of the Sculptor dwarf spheroidal galaxy
• The DART imaging and CaT survey of the Fornax Dwarf Spheroidal Galaxy
• Triaxial orbit based galaxy models with an application to the (apparent) decoupled core galaxy NGC 4365
• Velocity Dispersion Profiles of Seven Dwarf Spheroidal Galaxies
• Stellar Velocities in the Carina, Fornax, Sculptor and Sextans dSph Galaxies: Data from the Magellan/MMFS Survey
• A Baryonic Solution to the Missing Satellites Problem
• There is No Missing Satellites Problem
• Analysis and calibration of CaII triplet spectroscopy of Red Giant Branch stars from VLT/FLAMES observations
• Study of the Sextans dwarf spheroidal galaxy from the DART CaII triplet survey
• The Most Dark Matter Dominated Galaxies: Predicted Gamma-ray Signals from the Faintest Milky Way Dwarfs
• Unitarity Bounds and the Cuspy Halo Problem
• The fine-grained phase-space structure of Cold Dark Matter halos
• Internal kinematics and dynamical models of dwarf spheroidal galaxies around the Milky Way
• Dark matter annihilation and decay from non-spherical dark halos in the Galactic dwarf satellites
• Bayesian analysis of resolved stellar spectra: application to MMT/Hectochelle Observations of the Draco dwarf spheroidal
• Cores and Cusps in the Dwarf Spheroidals
• Orbit-based dynamical models of the Sculptor dSph galaxy
• Model comparison of the dark matter profiles of Fornax, Sculptor, Carina and Sextans
• Probing non-spherical dark halos in the Galactic dwarf galaxies
• 3D motions in the Sculptor dwarf galaxy as a glimpse of a new era
• Dynamical models for the Sculptor dwarf spheroidal in a Lambda CDM universe
• The shape of dark matter subhalos in the Aquarius simulations
• Analytical Solutions to the Mass-Anisotropy Degeneracy with Higher Order Jeans Analysis: A General Method
• Stellar 3-D kinematics in the Draco dwarf spheroidal galaxy
• Structural properties of non-spherical dark halos in Milky Way and Andromeda dwarf spheroidal galaxies
• Constraining black hole masses from stellar kinematics by summing over all possible distribution functions
• Recovering the mass profile and orbit anisotropy of mock dwarf galaxies with Schwarzschild modelling
• The effect of non-sphericity on mass and anisotropy measurements in dSph galaxies with Schwarzschild method

Cited by in corpus (3)

• A new implementation of the Schwarzschild method for constructing observationally-driven dynamical models of galaxies of all morphological types
• Dynamical Modeling of Galaxies and Supermassive Black Holes: Axisymmetry in Triaxial Schwarzschild Orbit Superposition Models
• Regular and chaotic orbits in axisymmetric stellar systems