Constraining the shape of Milky Way satellites with distance gradients

2022/02/02 by Zhaozhou An, S. E. Koposov, Sergey E. Koposov
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Classical mechanics #Dwarf galaxy #Dwarf spheroidal galaxy #Galaxies: Formation, Evolution, Phenomena #Galaxy #Local Group #Milky Way #Oblate spheroid #Photometry (optics) #Physics #Stars #Stellar, planetary, and galactic studies #astro-ph.GA

paper · pdf · doi:10.1093/mnras/stac308

published as Monthly Notices of the Royal Astronomical Society, Volume 511, Issue 3, April 2022, Pages 4316-4332 · 21 pages, 7 figures

openalex publication_date 2022/02/02 · arxiv created 2022/03/05 · arxiv updated 2022/03/08 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06

Abstract

We combine the Dark Energy Camera Legacy Survey (DECaLS) DR8 photometry with Gaia photometry to study the 3-D structure of Bootes I, Draco, Ursa Minor, Sextans and Sculptor dwarf galaxies using blue horizontal branch (BHB) stars as distance indicators. We construct a new colour-absolute magnitude of BHB stars that we use to measure the distance gradients within the body of the dwarf galaxies. We detect a statistically significant non-zero gradient only in Sextans and Sculptor. Through modeling of the gradient and 2-D density of the systems by triaxial Plummer models we find that the distance gradients in both dwarf galaxies are inconsistent with prolate shape, but compatible with oblate or triaxial shapes. In order to explain the observed gradients, oblate models of Sextans and Sculptor need to have a significant intrinsic ellipticity larger than 0.47 for Sextans and 0.46 for Sculptor. The flattened oblate shape may imply a significant anisotropy in velocity distribution in order to be consistent with the lack of significant velocity gradients in these systems.

Citations

• Beasts of the Southern Wild: Discovery of nine Ultra Faint satellites in the vicinity of the Magellanic Clouds
• THE EVOLUTION OF DWARF GALAXY SATELLITES WITH DIFFERENT DARK MATTER DENSITY PROFILES IN THE ERISMOD SIMULATIONS. I. THE EARLY INFALLS
• The Proper Motion of Sagittarius A*. II. The Mass of Sagittarius A*
• The alignment and shape of dark matter, stellar, and hot gas distributions in the EAGLE and cosmo-OWLS simulations
• Halos and galaxies in the standard cosmological model: results from the Bolshoi simulation
• Tying Dark Matter to Baryons with Self-Interactions
• Dark Matter Substructure within Galactic Halos
• Matplotlib: A 2D Graphics Environment
• MEASURING REDDENING WITH SLOAN DIGITAL SKY SURVEY STELLAR SPECTRA AND RECALIBRATING SFD
• Intrinsic Axis Ratio Distribution of Early‐Type Galaxies from the Sloan Digital Sky Survey
• emcee: The MCMC Hammer
• The impact of baryonic physics on the shape and radial alignment of substructures in cosmological dark matter haloes
• Galactic tides and the shape and orientation of dwarf galaxy satellites
• Systemic Proper Motions of Milky Way Satellites from Stellar Redshifts: The Carina, Fornax, Sculptor, and Sextans Dwarf Spheroidals
• The observed properties of dwarf galaxies in and around the Local Group
• Simulations of the formation, evolution and clustering of galaxies and quasars
• Star-Formation Histories, Abundances, and Kinematics of Dwarf Galaxies in the Local Group
• Galactic stellar haloes in the CDM model
• Gaia Data Release 2
• Overview of the DESI Legacy Imaging Surveys
• Stellar Density Profiles of Dwarf Spheroidal Galaxies
• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Small-Scale Challenges to the ΛCDM Paradigm
• Array Programming with NumPy
• Array programming with NumPy