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Connecting the Milky Way potential profile to the orbital time-scales and spatial structure of the Sagittarius Stream

Fardal, Mark A. and van der Marel, Roeland P. and Law, David R. and Sohn, Sangmo Tony and Sesar, Branimir and Hernitschek, Nina and Rix, Hans-Walter (2019) Connecting the Milky Way potential profile to the orbital time-scales and spatial structure of the Sagittarius Stream. Monthly Notices of the Royal Astronomical Society, 483 (4). pp. 4724-4741. ISSN 0035-8711. doi:10.1093/mnras/sty3428.

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Recent maps of the halo using RR Lyrae from Pan-STARRS1 depict the spatial structure of the Sagittarius stream, showing the leading and trailing stream apocentres differ in Galactocentric radius by a factor of 2, and also resolving substructure in the stream at these apocentres. Here we present dynamical models that reproduce these features of the stream in simple Galactic potentials. We find that debris at the apocentres must be dynamically young, being stripped off in pericentric passages either one or two orbital periods ago. The ratio of the leading and trailing apocentres is sensitive to both dynamical friction and the outer slope of the Galactic rotation curve. These dependencies can be understood with simple regularities connecting the apocentric radii, circular velocities, and orbital period of the progenitor. The effect of dynamical friction can be constrained using substructure within the leading apocentre. Our models are far from final; the errors allowed when sampling parameter space are deliberately generous, not every stream feature is reproduced, and we explore a limited set of potentials. Still, it is interesting that we consistently find the mass within 100 kpc to be ∼7×10^(11) M⊙⁠, with a nearly flat rotation curve between 50 and 100 kpc. This points to a more extended Galactic halo than assumed in some current models. We show one example model in various observational dimensions. A plot of velocity versus distance separates younger from older debris, and suggests that the young trailing debris will serve as an especially useful probe of the outer Galactic potential.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
van der Marel, Roeland P.0000-0001-7827-7825
Law, David R.0000-0002-9402-186X
Sesar, Branimir0000-0002-0834-3978
Hernitschek, Nina0000-0003-1681-0430
Rix, Hans-Walter0000-0003-4996-9069
Alternate Title:Connecting the Milky Way potential profile to the orbital timescales and spatial structure of the Sagittarius Stream
Additional Information:© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2018 December 14. Received 2018 December 11; in original form 2018 April 13. Published: 24 December 2018. We thank Tom Quinn and Joachim Stadel for the use of PKDGRAV and Josh Barnes for the ZENO package used in building the initial conditions. We thank Jo Bovy for making public the GALPY package and assisting with its use; Martin Weinberg assisted with use of the BIE code and provided a routine to initialize King models. This research made use of the open-source PYTHON package ASTROPY (Astropy Collaboration 2018), NUMPY, and MATPOTLIB. We thank Martin Weinberg, Gretchen Zwart, and Eric Winter for assistance with computing resources. Support for this work was provided by NASA through grants for programs GO-12564, GO-13443, GO-14235, and AR-15017 from the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS5-26555. HWR acknowledges support through the German Science Foundation (DFG) grant ‘SFB 881: The Milky Way System (A3)’.
Funding AgencyGrant Number
Space Telescope Science InstituteUNSPECIFIED
Association of Universities for Research in Astronomy (AURA)UNSPECIFIED
Deutsche Forschungsgemeinschaft (DFG)SFB 881
Subject Keywords:Galaxy: halo – Galaxy: kinematics and dynamics; galaxies: interactions – galaxies: kinematics and dynamics; galaxies: individual: Sagittarius
Issue or Number:4
Record Number:CaltechAUTHORS:20190411-150057928
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Official Citation:Mark A Fardal, Roeland P van der Marel, David R Law, Sangmo Tony Sohn, Branimir Sesar, Nina Hernitschek, Hans-Walter Rix, Connecting the Milky Way potential profile to the orbital time-scales and spatial structure of the Sagittarius Stream, Monthly Notices of the Royal Astronomical Society, Volume 483, Issue 4, March 2019, Pages 4724–4741,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:94670
Deposited By: Tony Diaz
Deposited On:11 Apr 2019 22:15
Last Modified:16 Nov 2021 17:06

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