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The Nature and Orbit of the Ophiuchus Stream | | B. Sesar
; J. Bovy
; E. J. Bernard
; N. Caldwell
; J. G. Cohen
; M. Fouesneau
; C. I. Johnson
; M. Ness
; A. M. N. Ferguson
; N. F. Martin
; H.-W. Rix
; E. F. Schlafly
; W. S. Burgett
; K. C. Chambers
; H. Flewelling
; K. W. Hodapp
; N. Kaiser
; E. A. Magnier
; I. Platais
; J. L. Tonry
; C. Waters
; R. F. G. Wyse
; | | Date: |
3 Jan 2015 | | Abstract: | The Ophiuchus stream is the most recently discovered stellar tidal stream in
the Milky Way (Bernard et al. 2014). 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 ($v_{los}sim290$ km s$^{-1}$),
kinematically-cold group ($sigma_{v_{los}}lesssim1$ km s$^{-1}$) of
$alpha-$enhanced and metal-poor stars (${
m [alpha/Fe]sim0.4}$ dex, ${
m
[Fe/H]sim-2.0}$ 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 that the stream extends in distance from 8 to 9.5 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 $sim13$ Gyr old, and that its initial stellar mass was
$sim2 imes10^4$ $M_sun$ (or at least $ga4 imes10^3$ $M_sun$). Assuming a
fiducial Milky Way potential, we fit an orbit to the stream which matches the
observed phase-space distribution, except for some tension in the proper
motions: the stream has an orbital period of $sim360$ Myr, and is on a fairly
eccentric orbit ($esim0.68$) with a pericenter of $sim3.5$ kpc and an
apocenter of $sim17.5$ 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 $sim250$ 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. | | Source: | arXiv, 1501.0581 | | Services: | Forum | Review | PDF | Favorites | |
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