Kavli Affiliate: Alexander P. Ji
| First 5 Authors: Yong Yang, Geraint F. Lewis, Denis Erkal, Ting S. Li, Andrew P. Li
| Summary:
The Ophiuchus stellar stream presents a puzzle due to its complicated
morphology, with a substructure perpendicular to the main track (spur), a
broadened tail (fanning), and a shorter than expected angular extent given its
old stellar population and short orbital period. The location of the stream
approaches the Galactic center, implying a possible connection between its
orbit and its unusual morphology. Here we demonstrate that the morphology of
Ophiuchus can be attributed to its interaction with the decelerating Galactic
bar, which leads to the flipping or transposition of its tidal tails. The short
length of the stream is the result of stars stripped in the ancient past still
remaining concentrated, and the spur, as well as the fanning, are composed of
either leading or trailing tails built up of stars released at different time
intervals. Our new spectroscopic data, obtained as part of the Southern Stellar
Stream Spectroscopic Survey $(S^5)$, and modeling of Ophiuchus indicate that,
in the presence of the bar, an initial leading tail can be redistributed to the
trailing side and vice versa, and the morphology of a stream can be reshaped.
This result confirms that the Galactic bar plays a vital role in reconstructing
the orbital behavior of streams passing close to the central region of the
Milky Way.
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