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arXiv · 1607.06465

The First Distance Constraint on the Renegade High Velocity Cloud Complex WD

J. E. G. Peek·Rongmon Bordoloi·Hugues Sana·Julia Roman-Duval·Jason Tumlinson·Yong Zheng
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Abstract

We present medium-resolution, near-ultraviolet VLT/FLAMES observations of the star USNO-A0600-15865535. We adapt a standard method of stellar typing to our measurement of the shape of the Balmer epsilon absorption line to demonstrates that USNO-A0600-15865535 is a blue horizontal branch star, residing in the lower stellar halo at a distance of 4.4 kpc from the Sun. We measure the H & K lines of singly-ionized calcium and find two isolated velocity components, one originating in the disk, and one associated with high-velocity cloud complex WD. This detection demonstrated that complex WD is closer than ~4.4 kpc and is the first distance constraint on the +100 km/s Galactic complex of clouds. We find that Complex WD is not in corotation with the Galactic disk as has been assumed for decades. We examine a number of scenarios, and find that the most likely is that Complex WD was ejected from the solar neighborhood and is only a few kpc from the Sun.

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J. E. G. Peek, Rongmon Bordoloi, Hugues Sana, Julia Roman-Duval, Jason Tumlinson, Yong Zheng. 2016-07-21. The First Distance Constraint on the Renegade High Velocity Cloud Complex WD. https://doi.org/10.3847/2041-8205/828/2/l20

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