Structural analysis of the Sextans dwarf spheroidal galaxy

Abstract

We present wide-field $g$ and $i$ band stellar photometry of the Sextans dwarf spheroidal galaxy and its surrounding area out to four times its half-light radius ($r_h=695$pc), based on images obtained with the Dark Energy Camera at the 4-m Blanco telescope at CTIO. We find clear evidence of stellar substructure associated with the galaxy, extending to a distance of $82\arcmin$ (2\,kpc) from its centre. We perform a statistical analysis of the over-densities and find three distinct features, as well as an extended halo-like structure, to be significant at the $99.7\%$ confidence level or higher. Unlike the extremely elongated and extended substructures surrounding the Hercules dwarf spheroidal galaxy, the over-densities seen around Sextans are distributed evenly about its centre, and do not appear to form noticeable tidal tails. Fitting a King model to the radial distribution of Sextans stars yields a tidal radius $r_t =83.2\arcmin\pm7.1\arcmin$ (2.08$\pm$0.18\,kpc), which implies the majority of detected substructure is gravitationally bound to the galaxy. This finding suggests that Sextans is not undergoing significant tidal disruption from the Milky Way, supporting the scenario in which the orbit of Sextans has a low eccentricity.

16 pages, 15 figures, 3 tables. Accepted to MNRAS 2016 April 20

References in corpus (18)

• Astrophysics Source Code Library
• The Kinematics of the Ultra-Faint Milky Way Satellites: Solving the Missing Satellite Problem
• Beasts of the Southern Wild: Discovery of nine Ultra Faint satellites in the vicinity of the Magellanic Clouds
• Introduction to astroML: Machine Learning for Astrophysics
• Globular Cluster Streams as Galactic High-Precision Scales - The Poster Child Palomar 5
• Co-orbiting satellite galaxy structures are still in conflict with the distribution of primordial dwarf galaxies
• The mass and velocity anisotropy of the Carina, Fornax, Sculptor and Sextans dwarf spheroidal galaxies
• Clean Kinematic Samples in Dwarf Spheroidals: An Algorithm for Evaluating Membership and Estimating Distribution Parameters When Contamination is Present
• A Hero's Dark Horse: Discovery of an Ultra-Faint Milky Way Satellite in Pegasus
• Mass modelling of dwarf spheroidal galaxies: the effect of unbound stars from tidal tails and the Milky Way
• A new distant Milky Way globular cluster in the Pan-STARRS1 3π survey
• Systemic Proper Motions of Milky Way Satellites from Stellar Redshifts: the Carina, Fornax, Sculptor and Sextans Dwarf Spheroidals
• The Star Formation History and Extended Structure of the Hercules Milky Way Satellite
• Reproducing properties of MW dSphs as descendants of DM-free TDGs
• On Kinematic Substructure in the Sextans Dwarf Spheroidal Galaxy
• A Hero's Little Horse: Discovery of a Dissolving Star Cluster in Pegasus
• Draco, a flawless dwarf galaxy
• Sailing under the Magellanic Clouds: A DECam View of the Carina Dwarf

Cited by in corpus (25)

• Fast radio bursts as giant pulses from young rapidly rotating pulsars
• The DECam Local Volume Exploration Survey: Overview and First Data Release
• The Outer Envelopes of Globular Clusters. II. NGC 1851, NGC 5824 and NGC 1261
• Dark Matter in Dwarf Spheroidal Galaxies and Indirect Detection: A Review
• Discovery of distant RR Lyrae stars in the Milky Way using DECam
• The star formation history of the Sextans dwarf spheroidal galaxy: a true fossil of the pre-reionization era
• Tracing the stellar component of low surface brightness Milky Way Dwarf Galaxies to their outskirts I: Sextans
• The Tucana dwarf spheroidal galaxy: not such a massive failure after all
• Exploding Satellites -- The Tidal Debris of the Ultra-Faint Dwarf Galaxy Hercules
• Population gradient in Sextans dSph: Comprehensive mapping of a dwarf galaxy by Suprime-Cam
• Structure of the Milky Way stellar halo out to its outer boundary with blue horizontal-branch stars
• Extended stellar substructure surrounding the Boötes I dwarf spheroidal galaxy
• Precision distances to dwarf galaxies and globular clusters from Pan-STARRS1 3$\pi$ RR Lyrae
• The Population of Pulsating Variable Stars in the Sextans Dwarf Spheroidal Galaxy
• Proper Motion of the Sextans Dwarf Galaxy from Subaru Suprime-Cam Data
• A panoramic view of the Local Group dwarf galaxy NGC 6822
• A Possible Relic Star Cluster in the Sextans Dwarf Galaxy
• Cold, old and metal-poor: New stellar substructures in the Milky Way's dwarf spheroidals
• Warm dark matter model with a few keV mass is bad for the too-big-to-fail problem
• A 3D view of dwarf galaxies with Gaia and VLT/FLAMES II. The Sextans dwarf spheroidal
• The impact of rare events on the chemical enrichment in dwarf galaxies
• Chemodynamics of BoötesI with $S^5$: Revised Velocity Gradient, Dark Matter Density, and Galactic Chemical Evolution Constraints
• A search for stellar structures around nine outer halo globular clusters in the Milky Way
• The tidal features of the classical Milky Way satellites: Expected in MOND but inconsistent with cold dark matter models
• Constraining the shape of Milky Way satellites with distance gradients