Joint Gas and Stellar Dynamical Models of WLM: An isolated dwarf galaxy within a cored, prolate DM halo

Abstract

We present multi-tracer dynamical models of the low mass ($M_{\ast }\sim 10^7$), isolated dwarf irregular galaxy WLM in order to simultaneously constrain the inner slope of the dark matter (DM) halo density profile ($\gamma$) and flattening ($q_{\mathrm{DM}}$), and the stellar orbital anisotropy (${\beta }_z,{\beta }_r$). For the first time, we show how jointly constraining the mass distribution from the HI gas rotation curve and solving the Jeans' equations with discrete stellar kinematics leads to a factor of $\sim 2$ reduction in the uncertainties on $\gamma$. The mass-anisotropy degeneracy is also partially broken, leading to reductions on uncertainty by $\sim 30\%$ on $M_{\mathrm{vir}}$ (and $\sim 70\%$ at the half-light radius) and $\sim 25\%$ on anisotropy. Our inferred value of $\gamma =0.3\pm 0.1$ is robust to the halo geometry, and in excellent agreement with predictions of stellar feedback driven DM core creation. The derived prolate geometry of the DM halo with $q_{\mathrm{DM}}=2\pm 1$ is consistent with $\Lambda$CDM simulations of dwarf galaxy halos. While self-interacting DM (SIDM) models with $\sigma /m_X\sim 0.6$ can reproduce this cored DM profile, the interaction events may sphericalise the halo. The simultaneously cored and prolate DM halo may therefore present a challenge for SIDM. Finally we find that the radial profile of stellar anisotropy in WLM (${\beta }_r$) follows a nearly identical trend of increasing tangential anisotropy to the classical dSphs, Fornax and Sculptor. Given WLM's orbital history, this result may call into question whether such anisotropy is a consequence of tidal stripping in only one pericentric passage or if it instead is a feature of the largely self-similar formation and evolutionary pathways for some dwarf galaxies.

arxiv version, published in MNRAS. 23 pages, 14 figures

References in corpus (25)

• Concentration, Spin and Shape of Dark Matter Haloes as a Function of the Cosmological Model: WMAP1, WMAP3 and WMAP5 results
• Understanding the Core-Halo Relation of Quantum Wave Dark Matter, $\psi$DM, from 3D Simulations
• Measuring the inclination and mass-to-light ratio of axisymmetric galaxies via anisotropic Jeans models of stellar kinematics
• The Star Formation Histories of Local Group Dwarf Galaxies I. Hubble Space Telescope / Wide Field Planetary Camera 2 Observations
• The kinematic status and mass content of the Sculptor dwarf spheroidal galaxy
• The DART imaging and CaT survey of the Fornax Dwarf Spheroidal Galaxy
• A mass-dependent density profile for dark matter haloes including the influence of galaxy formation
• Cosmological puzzle resolved by stellar feedback in high redshift galaxies
• NIHAO XI: Formation of Ultra-Diffuse Galaxies by outflows
• Dwarf galaxies in CDM and SIDM with baryons: observational probes of the nature of dark matter
• The abundance of (not just) dark matter haloes
• The mass and velocity anisotropy of the Carina, Fornax, Sculptor and Sextans dwarf spheroidal galaxies
• Dwarf Galaxy Dark Matter Density Profiles Inferred from Stellar and Gas Kinematics
• LITTLE THINGS in 3D: robust determination of the circular velocity of dwarf irregular galaxies
• SIDM on FIRE: Hydrodynamical Self-Interacting Dark Matter simulations of low-mass dwarf galaxies
• 3D motions in the Sculptor dwarf galaxy as a glimpse of a new era
• A discrete chemo-dynamical model of the dwarf spheroidal galaxy Sculptor: mass profile, velocity anisotropy and internal rotation
• When the Jeans don't fit: How stellar feedback drives stellar kinematics and complicates dynamical modeling in low-mass galaxies
• A Spitzer/IRAC Census of the Asymptotic Giant Branch Populations in Local Group Dwarfs. I. WLM
• A unified model for age-velocity dispersion relations in Local Group galaxies: Disentangling ISM turbulence and latent dynamical heating
• A High-Resolution Study of the HI Content of Local Group Dwarf Irregular Galaxy WLM
• A dwarf-dwarf merger and dark matter core as a solution to the Globular Cluster problems in the Fornax dSph
• Dwarf Galaxy Mass Estimators vs. Cosmological Simulations
• The effect of tides on the Sculptor dwarf spheroidal galaxy
• The Shape of Dark Matter Haloes III. Kinematics and Structure of the HI disc

Cited by in corpus (10)

• The Pandora project. I: the impact of radiation and cosmic rays on baryonic and dark matter properties of dwarf galaxies
• The Turn-Down of the Baryonic Tully-Fisher Relation and Changing Baryon Fractions at Low Galaxy Masses
• EDGE: The shape of dark matter haloes in the faintest galaxies
• A shallow dark matter halo in Ultra Diffuse Galaxy AGC 242019: are UDGs structurally similar to low surface brightness galaxies?
• Cuspy dark matter density profiles in massive dwarf galaxies
• A MARVEL-ous study of how well galaxy shapes reflect Dark Matter halo shapes in Cold Dark Matter Simulations
• Shapes of dark matter haloes with discrete globular cluster dynamics: The example of NGC 5128 (Centaurus A)
• Constraints on dark matter models from the stellar cores observed in ultra-faint dwarf galaxies: Self-interacting dark matter
• From gas to stars: MUSEings on the internal evolution of IC 1613
• Beyond single tracers: CNN-based inference of galaxy mass profiles from combined gas and stellar kinematics