To the Galactic Virial Radius with Hyper Suprime-Cam

Abstract

We exploit the exquisite, deep Hyper Suprime-Cam (HSC) imaging data to probe the Galactic halo out to 200 kpc. Using the ~100 square degree, multi-band photometry of the first HSC Wide survey data release, we identify blue horizontal branch (BHB) stars beyond 50 kpc in the halo. The presence of the Sagittarius (Sgr) stream in the HSC fields produces a notable excess of stars at the apocentre of the leading arm (~50-60 kpc). For fields excluding Sgr, the BHB counts are consistent with a continuation of a -4 power-law from the inner halo. However, we find that the majority of the non-Sgr BHB stars beyond 50 kpc reside in one 27 square degree HSC field called "VVDS". Curiously, this field is located close to the Magellanic plane, and we hypothesize that the excess of stars between 50 and 200 kpc could be associated with distant Magellanic debris. Indeed, without the VVDS, there are very few BHBs in the remaining portions of the Galaxy probed by the HSC. Accordingly, this scarcity of tracers is consistent with a significant decline in stellar density beyond 50 kpc, with a power-law of -4 or steeper.

arXiv comment13 pages, 11 figures. ApJ accepted

References in corpus (57)

• The cosmological simulation code GADGET-2
• The observed properties of dwarf galaxies in and around the Local Group
• Tracing Galaxy Formation with Stellar Halos I: Methods
• The Milky Way's Circular Velocity Curve to 60 kpc and an Estimate of the Dark Matter Halo Mass from Kinematics of ~2400 SDSS Blue Horizontal Branch Stars
• Are the Magellanic Clouds on their First Passage about the Milky Way?
• The Large, Oxygen-Rich Halos of Star-Forming Galaxies Are A Major Reservoir of Galactic Metals
• Weak Gravitational Lensing with COSMOS: Galaxy Selection and Shape Measurements
• Identification of A-colored Stars and Structure in the Halo of the Milky Way from SDSS Commissioning Data
• The Role of Dwarf Galaxy Interactions in Shaping the Magellanic System and Implications for Magellanic Irregulars
• The Masses of the Milky Way and Andromeda galaxies
• The Milky Way stellar halo out to 40 kpc : Squashed, broken but smooth
• The Magellanic Stream, High-Velocity Clouds and the Sculptor Group
• The radial velocity dispersion profile of the Galactic halo: Constraining the density profile of the dark halo of the Milky Way
• Substructure revealed by RR Lyraes in SDSS Stripe 82
• The Origin of the Magellanic Stream and Its Leading Arm
• Simulations of the Magellanic Stream in a First Infall Scenario
• "Skinny Milky Way, Please", says Sagittarius
• The feeble giant. Discovery of a large and diffuse Milky Way dwarf galaxy in the constellation of Crater
• Precession of the Sagittarius stream
• The Origin of the Magellanic Stream
• The Tidal Origin of the Magellanic Stream and the Possibility of a Stellar Counterpart
• Sagittarius Tidal Debris 90 kpc from the Galactic Center
• Exploring Halo Substructure with Giant Stars XI: The Tidal Tails of the Carina Dwarf Spheroidal and the Discovery of Magellanic Cloud Stars in the Carina Foreground
• Broken and unbroken: the Milky Way and M31 stellar haloes
• The 200 Degree-Long Magellanic Stream System
• The gravitational and hydrodynamical interaction between the LMC and the Galaxy
• Halo Mass and Assembly History Exposed in the Faint Outskirts: the Stellar and Dark Matter Haloes of Illustris Galaxies
• Ram Pressure Stripping of the Large Magellanic Cloud's Disk as a Probe of the Milky Way's Circumgalactic Medium
• The cold veil of the Milky Way stellar halo
• The velocity dispersion and mass profile of the Milky Way
• The radial profile and flattening of the Milky Way's stellar halo to $80$kpc from the SEGUE K-giant Survey
• At the survey limits: discovery of the Aquarius 2 dwarf galaxy in the VST ATLAS and the SDSS data
• Clouds, Streams and Bridges. Redrawing the blueprint of the Magellanic System with Gaia DR1
• Evidence for a Milky Way Tidal Stream Reaching Beyond 100 kpc
• The Eating Habits of Milky Way Mass Halos: Destroyed Dwarf Satellites and the Metallicity Distribution of Accreted Stars
• A new distant Milky Way globular cluster in the Pan-STARRS1 3π survey
• ATLAS lifts the Cup: Discovery of a New Milky Way satellite in Crater
• The Magellanic Stream System: I. Ram-pressure tails and the relics of the collision between the Magellanic Clouds
• Touching The Void: A Striking Drop in Stellar Halo Density Beyond 50 kpc
• Velocity Dispersion Profile of the Milky Way Halo
• Stellar streams around the Magellanic Clouds
• Constraining the orbital history of the Magellanic Clouds: A new bound scenario suggested by the tidal origin of the Magellanic Stream
• Substructure in the stellar halos of the Aquarius simulations
• The $>100$ kpc Distant Spur of the Sagittarius Stream and the Outer Virgo Overdensity, as Seen in PS1 RR Lyrae Stars
• Where Do Galaxies End?
• The Origin of the Microlensing Events Observed Towards the LMC and the Stellar Counterpart of the Magellanic Stream
• The Clouds are breaking: tracing the Magellanic system with Gaia DR1 Mira variables
• Identifying Blue Horizontal Branch Stars Using the z Filter
• Tracing the tidal streams of the Sagittarius dSph, and halo Milky Way features, with carbon-rich long-period variables
• Disentangling the dark matter halo from the stellar halo
• The Outer Halo of the Milky Way as Probed by RR Lyr Variables from the Palomar Transient Facility
• The accreted stellar halo as a window on halo assembly in L* galaxies
• The Stellar Density Profile of the Distant Galactic Halo
• The Most Distant Stars in the Milky Way
• Modified Virial Formulae and the Theory of Mass Estimators
• An extended view of the Pisces Overdensity from the SCUSS survey
• Mass estimators in the Gaia era

Cited by in corpus (21)

• Hunting for the Dark Matter Wake Induced by the Large Magellanic Cloud
• The Southern Stellar Stream Spectroscopic Survey ($S^5$): Overview, Target Selection, Data Reduction, Validation, and Early Science
• All-Sky Dynamical Response of the Galactic Halo to the Large Magellanic Cloud
• The mass of the Milky Way out to 100 kpc using halo stars
• Quantifying the Stellar Halo's Response to the LMC's Infall with Spherical Harmonics
• Constraints on the assembly history of the Milky Way's smooth, diffuse stellar halo from the metallicity-dependent, radially-dominated velocity anisotropy profiles probed with K giants and BHB stars using LAMOST, SDSS/SEGUE, and Gaia
• Milky Way Mass with K Giants and BHB Stars Using LAMOST, SDSS/SEGUE, and Gaia: 3D Spherical Jeans Equation and Tracer Mass Estimator
• The stellar halo of the Milky Way traced by blue horizontal-branch stars in the Subaru Hyper Suprime-Cam Survey
• Mapping the anisotropic Galactic stellar halo with Blue Horizontal Branch stars
• The Pristine survey -- VII. A cleaner view of the Galactic outer halo using blue horizontal branch stars
• Structure of the Milky Way stellar halo out to its outer boundary with blue horizontal-branch stars
• A-type stars in the Canada-France Imaging Survey II. Tracing the height of the disc at large distances with Blue Stragglers
• Modelling the Milky Way. I -- Method and first results fitting the thick disk and halo with DES-Y3 data
• The Far-Away Blues: Exploring the Furthest Extents of the Boötes I Ultra Faint Dwarf Galaxy
• HALO7D I: The Line of Sight Velocities of Distant Main Sequence Stars in the Milky Way Halo
• A LAMOST BHB Catalog and Kinematics Therein I: Catalog and Halo Properties
• Discovery of Magellanic Stellar Debris in the H3 Survey
• They Might Be Giants: An Efficient Color-Based Selection of Red Giant Stars
• A Pristine-UNIONS view on the Galaxy: Kinematics of the distant spur feature of the Sagittarius stream traced by Blue Horizontal Branch stars
• HALO7D III: Chemical Abundances of Milky Way Halo Stars from Medium Resolution Spectra
• The Pristine Survey -- XXVII. Journey to the Galactic outskirts -- Mapping the outer halo red giant stars down to the very metal-poor end