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

Slater, C.T.; Bell, E.F.; Schlafly, E.F.; Morganson, E.; Martin, N.F.; Rix, H.-W.; Peñarrubia, J.; Bernard, E.J.; Ferguson, A.M.N.; Martinez-Delgado, D.; Wyse, R.F.G.; Burgett, W.S.; Chambers, K.C.; Draper, P.W.; Hodapp, K.W.; Kaiser, N.; Magnier, E.A.; Metcalfe, N.; Price, P.A.; Tonry, J.L.; Wainscoat, R.J.; Waters, C.

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


C.T. Slater

E.F. Bell

E.F. Schlafly

E. Morganson

N.F. Martin

H.-W. Rix

J. Peñarrubia

E.J. Bernard

A.M.N. Ferguson

D. Martinez-Delgado

R.F.G. Wyse

W.S. Burgett

K.C. Chambers

K.W. Hodapp

N. Kaiser

E.A. Magnier

P.A. Price

J.L. Tonry

R.J. Wainscoat

C. Waters


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° and covering over 130° 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 that 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.


Slater, C., Bell, E., Schlafly, E., Morganson, E., Martin, N., Rix, H., …Waters, C. (2014). The Complex Structure of Stars in the Outer Galactic Disk as Revealed by Pan-STARRS1. Astrophysical Journal, 791(1),

Journal Article Type Article
Acceptance Date Jun 14, 2014
Publication Date Aug 10, 2014
Deposit Date Jun 16, 2015
Publicly Available Date Jul 1, 2015
Journal Astrophysical Journal
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 791
Issue 1
Keywords Galaxies: evolution, Galaxies: interactions, Galaxy: disk, Galaxy: structure.


Published Journal Article (2.2 Mb)

Copyright Statement
© 2014. The American Astronomical Society. All rights reserved.

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