The Complex Structure of Stars in the Outer Galactic Disk as revealed by Pan-STARRS1

Abstract

We present a panoptic view of the stellar structure in the Galactic disk's outer reaches commonly known as the Monoceros Ring, based on data from Pan-STARRS1. These observations clearly show the large extent of the stellar overdensities on both sides of the Galactic disk, extending between b = -25 and b = +35 degrees and covering over 130 degrees in Galactic longitude. The structure exhibits a complex morphology with both stream-like features and a sharp edge to the structure in both the north and the south. We compare this map to mock observations of two published simulations aimed at explaining such structures in the outer stellar disk, one postulating an origin as a tidal stream and the other demonstrating a scenario where the disk is strongly distorted by the accretion of a satellite. These morphological comparisons of simulations can link formation scenarios to observed structures, such as demonstrating that the distorted-disk model can produce thin density features resembling tidal streams. Although neither model produces perfect agreement with the observations--the tidal stream predicts material at larger distances which is not detected while in the distorted disk model the midplane is warped to an excessive degree--future tuning of the models to accommodate these latest data may yield better agreement.

10 pages, 7 figures. Accepted to ApJ. Key figures and data can be found at http://dept.astro.lsa.umich.edu/~ctslater/MRi/

References in corpus (10)

• Outer structure of the Galactic warp and flare: explaining the Canis Major over-density
• The QUEST RR Lyrae Survey II: The Halo Overdensities in the First Catalog
• Cold Dark Matter Substructure and Galactic Disks II: Dynamical Effects of Hierarchical Satellite Accretion
• Substructure in Tidal Streams; Tributaries in the Anticenter Ring
• The PAndAS Field of Streams: stellar structures in the Milky Way halo toward Andromeda and Triangulum
• The Nature and Origin of Substructure in the Outskirts of M31. I. Surveying the Stellar Content with HST/ACS
• On the Origin of Dynamically Cold Rings Around the Milky Way
• The AAT/WFI survey of the Monoceros Ring and Canis Major Dwarf galaxy: I. from l = (193 - 276)o
• No Excess of RR Lyrae Stars in the Canis Major Overdensity
• The Metallicity of the Monoceros Stream

Cited by in corpus (20)

• Rings and Radial Waves in the Disk of the Milky Way
• The Streams of the Gaping Abyss: A population of entangled stellar streams surrounding the Inner Galaxy
• A Synoptic Map of Halo Substructures from the Pan-STARRS1 3π Survey
• The Canada-France Imaging Survey: First results from the u-band component
• Disentangling the Galactic Halo with APOGEE: II. Chemical and Star Formation Histories for the Two Distinct Populations
• Tails and streams around the Galactic globular clusters NGC1851, NGC1904, NGC2298 and NGC2808
• Exploring Halo Substructure with Giant Stars: The Nature of the Triangulum-Andromeda Stellar Features
• The Pristine survey -- XXIII. Data Release 1 and an all-sky metallicity catalogue based on Gaia DR3 BP/RP spectro-photometry
• The fall of the Northern Unicorn: Tangential motions in the Galactic Anti-centre with SDSS and Gaia
• An ever-present $Gaia$ snail shell triggered by a dark matter wake
• The Stellar Density Profile of the Distant Galactic Halo
• At a Crossroads: Stellar Streams in the South Galactic Cap
• Cresting the wave: Proper motions of the Eastern Banded Structure
• The outer disc in shambles: blind detection of Monoceros and ACS with Gaia's astrometric sample
• Estimating the local dark matter density in a non-axisymmetric wobbling disc
• Exploring the Galactic Anticenter substructure with LAMOST & Gaia DR2
• The disruption of the low-mass globular cluster E3
• A Megacam Survey of Outer Halo Satellites. IV. Two foreground populations possibly associated with the Monoceros substructure in the direction of NGC2419 and Koposov2
• Tomography of stellar halos: what does anisotropy in a stellar halo tell us?
• Bending Waves in Velocity Space: a First Look at the THINGS sample