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Evidence of Fanning in the Ophiuchus Stream

Sesar, Branimir and Price-Whelan, Adrian M. and Cohen, Judith G. and Rix, Hans-Walter and Pearson, Sarah and Johnston, Kathryn V. and Bernard, Edouard J. and Ferguson, Annette M. N. and Martin, Nicolas F. and Slater, Colin T. and Chambers, Kenneth C. and Flewelling, Heather and Wainscoat, Richard J. and Waters, Christopher (2016) Evidence of Fanning in the Ophiuchus Stream. Astrophysical Journal Letters, 816 (1). Art. No.L4. ISSN 2041-8205.

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The Ophiuchus stellar stream presents a dynamical puzzle: its old stellar populations (~12 Gyr) cannot be reconciled with (1) its orbit in a simple model for the Milky Way potential and (2) its short angular extent, both of which imply that the observed stream formed within the last <l Gyr. Recent theoretical work has shown that streams on chaotic orbits may abruptly fan out near their apparent ends; stars in these fans are dispersed in both position and velocity and may be difficult to associate with the stream. Here we present the first evidence of such stream-fanning in the Ophiuchus stream, traced by four blue horizontal branch stars beyond the apparent end of the stream. These stars stand out from the background by their high velocities (v_(los) > 230 km s^(−1)) against ~40 other stars: their velocities are comparable to those of the stream, but would be exceptional if they were unrelated halo stars. Their positions and velocities are, however, inconsistent with simple extrapolation of the observed cold, high-density portion of the stream. These observations suggest that stream-fanning may be a real, observable effect and, therefore, that Ophiuchus may be on a chaotic orbit. They also show that the Ophiuchus stream is more extended and hence dynamically older than previously thought, easing the stellar population versus dynamical age tension.

Item Type:Article
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URLURL TypeDescription Paper
Sesar, Branimir0000-0002-0834-3978
Price-Whelan, Adrian M.0000-0003-0872-7098
Cohen, Judith G.0000-0002-8039-4673
Rix, Hans-Walter0000-0003-4996-9069
Johnston, Kathryn V.0000-0001-6244-6727
Martin, Nicolas F.0000-0002-1349-202X
Chambers, Kenneth C.0000-0001-6965-7789
Flewelling, Heather0000-0002-1050-4056
Wainscoat, Richard J.0000-0002-1341-0952
Waters, Christopher0000-0003-1989-4879
Additional Information:© 2016 American Astronomical Society. Received 2015 October 12; accepted 2015 December 6; published 2015 December 28. B.S. acknowledges funding from the European Research Council under the European Unions Seventh Framework Programme (FP 7) ERC Grant Agreement n. . A.P.W. is supported by a National Science Foundation Graduate Research Fellowship under Grant No. 11-44155. The Pan-STARRS1 Surveys (PS1) have been made possible through contributions by the Institute for Astronomy, the University of Hawaii, the Pan-STARRS Project Office, the Max-Planck Society and its participating institutes, the Max Planck Institute for Astronomy, Heidelberg and the Max Planck Institute for Extraterrestrial Physics, Garching, The Johns Hopkins University, Durham University, the University of Edinburgh, the Queen's University Belfast, the Harvard-Smithsonian Center for Astrophysics, the Las Cumbres Observatory Global Telescope Network Incorporated, the National Central University of Taiwan, the Space Telescope Science Institute, and the National Aeronautics and Space Administration under Grant No. NNX08AR22G issued through the Planetary Science Division of the NASA Science Mission Directorate, the National Science Foundation Grant No. AST-1238877, the University of Maryland, Eotvos Lorand University (ELTE), and the Los Alamos National Laboratory. Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. Based on observations collected at the German-Spanish Astronomical Center, Calar Alto, jointly operated by the Max-Planck-Institut für Astronomie Heidelberg and the Instituto de Astrofísica de Andaluca (CSIC). Facilities: PS1 - Panoramic Survey Telescope and Rapid Response System Telescope #1 (Pan-STARRS), Keck:I - KECK I Telescope (DEIMOS - ), CAO:3.5m - (TWIN - ).
Funding AgencyGrant Number
European Research Council (ERC)321035
NSF Graduate Research Fellowship11-44155
Institute for AstronomyUNSPECIFIED
University of HawaiiUNSPECIFIED
Max-Planck SocietyUNSPECIFIED
Max Planck Institute for AstronomyUNSPECIFIED
Max Planck Institute for Extraterrestrial PhysicsUNSPECIFIED
Johns Hopkins UniversityUNSPECIFIED
Durham UniversityUNSPECIFIED
University of EdinburghUNSPECIFIED
Queen’s University BelfastUNSPECIFIED
Harvard-Smithsonian Center for AstrophysicsUNSPECIFIED
Cumbres Observatory Global Telescope Network IncorporatedUNSPECIFIED
National Central University (Taiwan)UNSPECIFIED
Space Telescope Science InstituteUNSPECIFIED
University of MarylandUNSPECIFIED
Eotvos Lorand UniversityUNSPECIFIED
Los Alamos National LaboratoryUNSPECIFIED
W.M. Keck FoundationUNSPECIFIED
Subject Keywords:Galaxy: halo; Galaxy: kinematics and dynamics; Galaxy: structure; globular clusters: general
Issue or Number:1
Record Number:CaltechAUTHORS:20160226-075259066
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Official Citation:Branimir Sesar et al 2016 ApJ 816 L4
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:64788
Deposited By: Ruth Sustaita
Deposited On:29 Feb 2016 20:56
Last Modified:09 Mar 2020 13:19

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