Skip to main content

Research Repository

Advanced Search

The Geometry of the Sagittarius Stream from Pan-STARRS1 3π RR Lyrae

Hernitschek, Nina; Sesar, Branimir; Rix, Hans-Walter; Belokurov, Vasily; Martinez-Delgado, David; Martin, Nicolas F.; Kaiser, Nick; Hodapp, Klaus; Chambers, Kenneth C.; Wainscoat, Richard; Magnier, Eugene; Kudritzki, Rolf-Peter; Metcalfe, Nigel; Draper, Peter W.

The Geometry of the Sagittarius Stream from Pan-STARRS1 3π RR Lyrae Thumbnail


Nina Hernitschek

Branimir Sesar

Hans-Walter Rix

Vasily Belokurov

David Martinez-Delgado

Nicolas F. Martin

Nick Kaiser

Klaus Hodapp

Kenneth C. Chambers

Richard Wainscoat

Eugene Magnier

Rolf-Peter Kudritzki


We present a comprehensive and precise description of the Sagittarius (Sgr) stellar stream's 3D geometry as traced by its old stellar population. This analysis draws on the sample of ∼44,000 RR Lyrae (RRab) stars from the Pan-STARRS1 (PS1) 3π survey (Hernitschek et al. 2016,Sesar et al. 2017b), which is ∼80% complete and ∼90% pure within 80~kpc, and extends to ≳120~kpc with a distance precision of ∼3%. A projection of RR Lyrae stars within |B~|⊙<9∘ of the Sgr stream's orbital plane reveals the morphology of both the leading and the trailing arms at very high contrast, across much of the sky. In particular, the map traces the stream near-contiguously through the distant apocenters. We fit a simple model for the mean distance and line-of-sight depth of the Sgr stream as a function of the orbital plane angle Λ~⊙, along with a power-law background-model for the field stars. This modeling results in estimates of the mean stream distance precise to ∼1% and it resolves the stream's line-of-sight depth. These improved geometric constraints can serve as new constraints for dynamical stream models.


Hernitschek, N., Sesar, B., Rix, H., Belokurov, V., Martinez-Delgado, D., Martin, N. F., …Draper, P. W. (2017). The Geometry of the Sagittarius Stream from Pan-STARRS1 3π RR Lyrae. Astrophysical Journal, 850(1), Article 96.

Journal Article Type Article
Acceptance Date Oct 23, 2017
Online Publication Date Nov 21, 2017
Publication Date Nov 21, 2017
Deposit Date Dec 7, 2017
Publicly Available Date Dec 7, 2017
Journal Astrophysical Journal
Print ISSN 0004-637X
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 850
Issue 1
Article Number 96


Published Journal Article (10 Mb)

Copyright Statement
© 2017. The American Astronomical Society. All rights reserved.

You might also like

Downloadable Citations