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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 729994.0, MPI für Astronomie / Publikationen_mpia
The nature and orbit of the Ophiuchus stream
Authors:Sesar, B.; Bovy, J.; Bernard, E. J.; Caldwell, N.; Cohen, J. G.; Fouesneau, M.; Johnson, C. I.; Ness, M.; Ferguson, A. M. N.; Martin, N. F.; Price-Whelan, A. M.; Rix, H.-W.; Schlafly, E. F.; Burgett, W. S.; Chambers, K. C.; Flewelling, H.; Hodapp, K. W.; Kaiser, N.; Magnier, E. A.; Platais, I.; Tonry, J. L.; Waters, C.; Wyse, R. F. G.
Date of Publication (YYYY-MM-DD):2015
Title of Journal:The Astrophysical Journal
Start Page:id. 59 (16 pp)
Audience:Not Specified
Abstract / Description:The Ophiuchus stream is a recently discovered stellar tidal stream in the Milky Way. We present high-quality spectroscopic data for 14 stream member stars obtained using the Keck and MMT telescopes. We confirm the stream as a fast moving (vlos ∼ 290 km s‑1), kinematically cold group ({σ }{v{los}}≲ 1 km s‑1) of α-enhanced and metal-poor stars ([α/Fe] ∼ 0.4 dex, [Fe/H] ∼ ‑2.0 dex). Using a probabilistic technique, we model the stream simultaneously in line-of-sight velocity, color–magnitude, coordinate, and proper motion space, and so determine its distribution in 6D phase-space. We find that the stream extends in distance from 7.5 to 9 kpc from the Sun; it is 50 times longer than wide, merely appearing highly foreshortened in projection. The analysis of the stellar population contained in the stream suggests that it is ∼12 Gyr old, and that its initial stellar mass was ∼2 × 104 M (or at least ≳7 × 103 M). Assuming a fiducial Milky Way potential, we fit an orbit to the stream that matches the observed phase-space distribution, except for some tension in the proper motions: the stream has an orbital period of ∼350 Myr, and is on a fairly eccentric orbit (e ∼ 0.66) with a pericenter of ∼3.5 kpc and an apocenter of ∼17 kpc. The phase-space structure and stellar population of the stream show that its progenitor must have been a globular cluster that was disrupted only ∼240 Myr ago. We do not detect any significant overdensity of stars along the stream that would indicate the presence of a progenitor, and conclude that the stream is all that is left of the progenitor.
Free Keywords:Galaxy: halo; Galaxy: kinematics and dynamics; Galaxy: structure; globular clusters: general
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
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