Constraining the shape of Milky Way satellites with distance gradients

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.

arXiv comment21 pages, 7 figures

References in corpus (98)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• emcee: The MCMC Hammer
• Gaia Data Release 2. Summary of the contents and survey properties
• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• The Gaia mission
• Simulating the joint evolution of quasars, galaxies and their large-scale distribution
• Dark Matter Substructure in Galactic Halos
• Where are the missing galactic satellites?
• Dwarf Galaxies of the Local Group
• Local Kinematics and the Local Standard of Rest
• The observed properties of dwarf galaxies in and around the Local Group
• Overview of the DESI Legacy Imaging Surveys
• Cold and Fuzzy Dark Matter
• Monitoring stellar orbits around the Massive Black Hole in the Galactic Center
• Small-Scale Challenges to the $\Lambda$CDM Paradigm
• Too big to fail? The puzzling darkness of massive Milky Way subhaloes
• From dwarf spheroidals to cDs: Simulating the galaxy population in a LCDM cosmology
• Star Formation Histories, Abundances and Kinematics of Dwarf Galaxies in the Local Group
• The SAURON project - IV. The mass-to-light ratio, the virial mass estimator and the fundamental plane of elliptical and lenticular galaxies
• Halo Formation in Warm Dark Matter Models
• A 2MASS All-Sky View of the Sagittarius Dwarf Galaxy: I. Morphology of the Sagittarius Core and Tidal Arms
• The Dark Energy Camera
• Halos and galaxies in the standard cosmological model: results from the Bolshoi simulation
• Observational and Theoretical Constraints on Singular Dark Matter Halos
• The Proper Motion of Sgr A*: II. The Mass of Sgr A*
• The SAURON project -- IX. A kinematic classification for early-type galaxies
• The Milky Way's bright satellites as an apparent failure of LCDM
• The ATLAS3D project - III. A census of the stellar angular momentum within the effective radius of early-type galaxies: unveiling the distribution of Fast and Slow Rotators
• Gaia Data Release 2: Photometric content and validation
• Accurate masses for dispersion-supported galaxies
• A Universal Mass Profile for Dwarf Spheroidal Galaxies?
• A Method for Measuring (Slopes of) the Mass Profiles of Dwarf Spheroidal Galaxies
• Cuspy No More: How Outflows Affect the Central Dark Matter and Baryon Distribution in Lambda CDM Galaxies
• Galactic stellar haloes in the CDM model
• The Faintest Dwarf Galaxies
• Beasts of the Southern Wild: Discovery of nine Ultra Faint satellites in the vicinity of the Magellanic Clouds
• The Dark Energy Survey Data Release 1
• The Observed properties of Dark Matter on small spatial scales
• Internal and External Alignment of the Shapes and Angular Momenta of LCDM Halos
• The kinematic status and mass content of the Sculptor dwarf spheroidal galaxy
• Discovery of an Unusual Dwarf Galaxy in the Outskirts of the Milky Way
• The Milky Way stellar halo out to 40 kpc : Squashed, broken but smooth
• Tidal stirring and the origin of dwarf spheroidals in the Local Group
• FIRE in the Field: Simulating the Threshold of Galaxy Formation
• A MegaCam Survey of Outer Halo Satellites. III. Photometric and Structural Parameters
• Leo V: A Companion of a Companion of the Milky Way Galaxy
• The mass of the Milky Way from satellite dynamics
• Tying Dark Matter to Baryons with Self-interactions
• The Blue Tip of the Stellar Locus: Measuring Reddening with the SDSS
• Gravitational probes of dark matter physics
• Study of the Sextans dwarf spheroidal galaxy from the DART CaII triplet survey
• Early Gas Stripping as the Origin of the Darkest Galaxies in the Universe
• Rotation and anisotropy of galaxies revisited
• Blue horizontal branch stars in the Sloan Digital Sky Survey: I. Sample selection and structure in the Galactic halo
• The shapes, orientation, and alignment of Galactic dark matter subhalos
• The alignment and shape of dark matter, stellar, and hot gas distributions in the EAGLE and cosmo-OWLS simulations
• Kinematics of Milky Way Satellites in a Lambda Cold Dark Matter Universe
• Clean Kinematic Samples in Dwarf Spheroidals: An Algorithm for Evaluating Membership and Estimating Distribution Parameters When Contamination is Present
• Mismatch and Misalignment: Dark Haloes and Satellites of Disc Galaxies
• The Southern Stellar Stream Spectroscopic Survey ($S^5$): Overview, Target Selection, Data Reduction, Validation, and Early Science
• The Signature of Galactic Tides in Local Group Dwarf Spheroidals
• Systematics in virial mass estimators for pressure-supported systems
• The mass distribution of the Fornax dSph: constraints from its globular cluster distribution
• At the survey limits: discovery of the Aquarius 2 dwarf galaxy in the VST ATLAS and the SDSS data
• Too Big To Fail in Light of Gaia
• The link between the assembly of the inner dark matter halo and the angular momentum evolution of galaxies in the EAGLE simulation
• The shapes of galaxies in the Sloan Digital Sky Survey
• Systemic Proper Motions of Milky Way Satellites from Stellar Redshifts: the Carina, Fornax, Sculptor and Sextans Dwarf Spheroidals
• Evidence from Intrinsic Shapes for Two Families of Elliptical Galaxies
• The relationship between the morphology and kinematics of galaxies and its dependence on dark matter halo structure in EAGLE
• A New Milky Way Satellite Discovered In The Subaru/Hyper Suprime-Cam Survey
• Exploring Halo Substructure with Giant Stars VIII: The Extended Structure of the Sculptor Dwarf Spheroidal Galaxy
• The impact of baryonic discs on the shapes and profiles of self-interacting dark matter halos
• Distant field BHB stars and the mass of the Galaxy I: Classification of halo A-type stars
• Tidal disruption of globular clusters in dwarf galaxies with triaxial dark matter haloes
• Deep Wide-Field Imaging down to the oldest Main Sequence Turnoffs in the Sculptor dwarf spheroidal galaxy
• The impact of baryonic physics on the shape and radial alignment of substructures in cosmological dark matter haloes
• The shape of dark matter subhalos in the Aquarius simulations
• The Absence of Extra-Tidal Structure in the Sculptor Dwarf Spheroidal Galaxy
• Galactic Tides and the Shape and Orientation of Dwarf Galaxy Satellites
• Multiple stellar population in the Sextans dwarf spheroidal galaxy?
• Tracing the stellar component of low surface brightness Milky Way Dwarf Galaxies to their outskirts I: Sextans
• Appearances can be deceiving: clear signs of accretion in the seemingly ordinary Sextans dSph
• Structural analysis of the Sextans dwarf spheroidal galaxy
• Stellar Density Profiles of Dwarf Spheroidal Galaxies
• Population gradient in Sextans dSph: Comprehensive mapping of a dwarf galaxy by Suprime-Cam
• Intrinsic Axis Ratio Distribution of Early-type Galaxies From Sloan Digital Sky Survey
• Determination of Dark Matter Halo Mass from Dynamics of Satellite Galaxies
• A new calibration for the Blue Horizontal Branch
• The intrinsic ellipticity of dwarf spheroidal galaxies: constraints from the Andromeda system
• The Population of Pulsating Variable Stars in the Sextans Dwarf Spheroidal Galaxy
• The evolution of dwarf galaxy satellites with different dark matter density profiles in the ErisMod simulations. I. The early infalls
• A fresh look at the RR Lyrae population in the Draco dwarf spheroidal galaxy with Gaia
• The shapes and alignments of the satellites of the Milky Way and Andromeda
• A Possible Relic Star Cluster in the Sextans Dwarf Galaxy
• Testing $\Lambda$CDM With Dwarf Galaxy Morphology