Stellar Substructures around the Hercules Dwarf Spheroidal Galaxy

Abstract

We present deep $g,i$-band DECam stellar photometry of the Hercules Milky Way satellite galaxy, and its surrounding field, out to a radial distance of 5.4 times the tidal radius. We have identified nine extended stellar substructures associated with the dwarf; preferentially distributed along the major axis of the galaxy. Two significant over-densities lie outside the 95\% confidence band for the likely orbital path of the galaxy and appear to be free-floating tidal debris. We estimate the luminosity of the new stellar substructures, and find that approximately the same amount of stellar flux is lying in these extended structures as inside the main body of Hercules. We also analyse the distribution of candidate blue-horizontal-branch stars and find agreement with the alignment of the substructures at a confidence level greater than 98\%. Our analysis provides a quantitative demonstration that Hercules is a strongly tidally disrupted system, with noticeable stellar features at least 1.9 kpc away from the galaxy.

13 pages, 13 figures, accepted for publication in ApJ

References in corpus (19)

• The Dartmouth Stellar Evolution Database
• The Kinematics of the Ultra-Faint Milky Way Satellites: Solving the Missing Satellite Problem
• Cats and Dogs, Hair and A Hero: A Quintet of New Milky Way Companions
• A Vast Thin Plane of Co-rotating Dwarf Galaxies Orbiting the Andromeda Galaxy
• The Tidal Evolution of Local Group Dwarf Spheroidals
• An Orphan in the "Field of Streams"
• The Highly Unusual Chemical Composition of the Hercules Dwarf Spheroidal Galaxy
• The spatial distribution of the Milky Way and Andromeda satellite galaxies
• Co-orbiting satellite galaxy structures are still in conflict with the distribution of primordial dwarf galaxies
• Substructure in Tidal Streams; Tributaries in the Anticenter Ring
• Modeling The Structure And Dynamics of Dwarf Spheroidal Galaxies with Dark Matter And Tides
• Mass modelling of dwarf spheroidal galaxies: the effect of unbound stars from tidal tails and the Milky Way
• Discs of Satellites: the new 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
• Sailing under the Magellanic Clouds: A DECam View of the Carina Dwarf
• Two New Halo Debris Streams in the Sloan Digital Sky Survey
• Life and death of a hero - Lessons learned from modeling the dwarf spheroidal Hercules: an incorrect orbit?
• A bag of tricks: Using proper motions of Galactic stars to identify the Hercules ultra-faint dwarf galaxy members

Cited by in corpus (10)

• One Law To Rule Them All: The Radial Acceleration Relation of Galaxies
• The Outer Envelopes of Globular Clusters. II. NGC 1851, NGC 5824 and NGC 1261
• Metallicity and $\alpha$-element Abundance Gradients along the Sagittarius Stream as Seen by APOGEE
• A detailed study of Andromeda XIX, an extreme local analogue of ultra diffuse galaxies
• Mapping the Tidal Disruption of the Hercules Dwarf: A Wide-Field DECam Imaging Search for RR Lyrae Stars
• Tracing the stellar component of low surface brightness Milky Way Dwarf Galaxies to their outskirts I: Sextans
• Exploding Satellites -- The Tidal Debris of the Ultra-Faint Dwarf Galaxy Hercules
• Proper Motion of the Sextans Dwarf Galaxy from Subaru Suprime-Cam Data
• Faint Stars in a Faint Galaxy: I. Ultra Deep Photometry of the Boötes I Ultra Faint Dwarf Galaxy
• Quantifying Departures from Equilibrium with the Spherical Jeans Equation