Three-dimensional structure of the Sagittarius dSph core from RR Lyrae

Abstract

We obtain distances to a sample of RR Lyrae in the central core of the Sagittarius dwarf spheroidal galaxy from OGLE data. We use these distances, along with RR Lyrae from \emph{Gaia} DR2, to measure the shape of the stellar distribution within the central $\sim$ 2 kpc. The best-fit stellar distribution is triaxial, with axis ratios 1 : 0.76 : 0.43. A prolate spheroid model is ruled out at high statistical significance relative to the triaxial model. The major axis is aligned nearly parallel to the sky plane as seen by an Earth-based observer and is nearly perpendicular to the direction of the Galactic center. This result may be compared to cosmological simulations which generally predict that the major axis of the dark matter distribution of subhalos is aligned with the Galactic center. The triaxial structure that we obtain can provide important constraints on the Sagittarius progenitor, as well as the central dark matter distribution under the assumption of dynamical equilibrium.

arXiv comment11 pages, 7 figures, accepted in MNRAS

References in corpus (45)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Astropy: A Community Python Package for Astronomy
• Gaia Data Release 2. Summary of the contents and survey properties
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• The Gaia mission
• MultiNest: an efficient and robust Bayesian inference tool for cosmology and particle physics
• The observed properties of dwarf galaxies in and around the Local Group
• Multimodal nested sampling: an efficient and robust alternative to MCMC methods for astronomical data analysis
• X-ray spectral modelling of the AGN obscuring region in the CDFS: Bayesian model selection and catalogue
• A 2MASS All-Sky View of the Sagittarius Dwarf Galaxy: I. Morphology of the Sagittarius Core and Tidal Arms
• A geometric distance measurement to the Galactic Center black hole with 0.3% uncertainty
• Intrinsic iron spread and a new metallicity scale for Globular Clusters
• Gaia Data Release 2: Kinematics of globular clusters and dwarf galaxies around the Milky Way
• The Sagittarius Dwarf Galaxy: a Model for Evolution in a Triaxial Milky Way Halo
• Magellanic Cloud Structure from Near-IR Surveys I: The Viewing Angles of the LMC
• The Kinematics, Orbit, and Survival of the Sagittarius Dwarf Spheroidal Galaxy
• The Disruption of the Sagittarius Dwarf Galaxy.
• Gaia DR2 Proper Motions of Dwarf Galaxies within 420 kpc: Orbits, Milky Way Mass, Tidal Influences, Planar Alignments, and Group Infall
• Precession of the Sagittarius stream
• The Sagittarius Streams in the Southern Galactic Hemisphere
• Metal Abundances, Radial Velocities and other Physical Characteristics for the RR Lyrae Stars in the Kepler Field
• The shapes, orientation, and alignment of Galactic dark matter subhalos
• Tidal Tails Test the Equivalence Principle in the Dark Sector
• The shape of the Galactic halo with $Gaia$ DR2 RR Lyrae. Anatomy of an ancient major merger
• Re-Assembling the Sagittarius Dwarf Galaxy
• Kinematics of Milky Way Satellites in a Lambda Cold Dark Matter Universe
• Galactic Indigestion: Numerical Simulations of the Milky Way's Closest Neighbor
• Internal kinematics and dynamical models of dwarf spheroidal galaxies around the Milky Way
• On the distance of the globular cluster M4 (NGC 6121) using RR Lyrae stars: I. optical and near-infrared Period-Luminosity and Period-Wesenheit relations
• A Tail of Two Populations: Chemo-dynamics of the Sagittarius Stream and Implications for its Original Mass
• The inner structure and kinematics of the Sagittarius dwarf galaxy as a product of tidal stirring
• The $>100$ kpc Distant Spur of the Sagittarius Stream and the Outer Virgo Overdensity, as Seen in PS1 RR Lyrae Stars
• Predicted Extension of the Sagittarius Stream to the Milky Way Virial Radius
• The Geometry of Sagittarius Stream from Pan-STARRS1 3$\pi$ RR Lyrae
• No evidence for internal rotation in the remnant core of the Sagittarius dwarf
• A Pan-STARRS1 View of the Bifurcated Sagittarius Stream
• A 2MASS All-Sky View of the Sagittarius Dwarf Galaxy: VII. Kinematics of the Main Body of the Sagittarius dSph
• Discovery of a Dynamical Cold Point in the Heart of the Sagittarius dSph Galaxy with Observations from the APOGEE Project
• Galactic Tides and the Shape and Orientation of Dwarf Galaxy Satellites
• Structural properties of non-spherical dark halos in Milky Way and Andromeda dwarf spheroidal galaxies
• Plan beta: Core or Cusp?
• The shapes and alignments of the satellites of the Milky Way and Andromeda
• Geometry of the Large Magellanic Cloud Using Multi- wavelength Photometry of Classical Cepheids
• Testing $\Lambda$CDM With Dwarf Galaxy Morphology
• Distance, reddening and three dimensional structure of the SMC - I: Using RRab stars

Cited by in corpus (12)

• Accurate distances to Galactic globular clusters through a combination of Gaia EDR3, HST and literature data
• The last breath of the Sagittarius dSph
• Revealing the Structure and Internal Rotation of the Sagittarius Dwarf Spheroidal Galaxy with Gaia and Machine Learning
• The period--luminosity relation for Mira variables in the Milky Way using Gaia DR3: a further distance anchor for $H_0$
• Studies of RR Lyrae Variables in Binary Systems. I.: Evidence of a Trimodal Companion Mass Distribution
• The metallicity distribution in the core of the Sagittarus dwarf spheroidal: minimising the metallicity biases
• Discovery of 18 stars with -3.10 < [Fe/H] < -1.45 in the Sagittarius dwarf galaxy
• The Pristine Inner Galaxy Survey (PIGS) IV: A photometric metallicity analysis of the Sagittarius dwarf spheroidal galaxy
• On the gamma-ray emission from the core of the Sagittarius dwarf galaxy
• Kinematics of the Sagittarius Dwarf Spheroidal core: A 5D Analysis for a 6D Methodology with Gaia DR3
• Timing Mass of the Local Group
• rrlfe: Software for Generating and Applying Metallicity Calibrations for RR Lyrae Variable Stars Across a Wide Range of Phases and Temperatures