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Velocity Variations in the Phoenix-Hermus Star Stream

Carlberg, R. G. and Grillmair, C. J. (2016) Velocity Variations in the Phoenix-Hermus Star Stream. Astrophysical Journal, 830 (2). Art. No. 135. ISSN 0004-637X.

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Measurements of velocity and density perturbations along stellar streams in the Milky Way provide a time-integrated measure of dark matter substructure at larger galactic radius than the complementary instantaneous inner-halo strong lensing detection of dark matter sub-halos in distant galaxies. An interesting case to consider is the proposed Phoenix–Hermus star stream, which is long, thin, and on a nearly circular orbit, making it a particular good target to study for velocity variations along its length. In the presence of dark matter sub-halos, the stream velocities are significantly perturbed in a manner that is readily understood with the impulse approximation. A set of simulations shows that only sub-halos above a few 10^7 M_⊙ lead to reasonably long-lived observationally detectable velocity variations of amplitude of order 1 km s^(−1), with an average of about one visible hit per (two-armed) stream over a 3 Gyr interval. An implication is that globular clusters themselves will not have a visible impact on the stream. Radial velocities have the benefit of being completely insensitive to distance errors. Distance errors scatter individual star velocities perpendicular and tangential to the mean orbit, but their mean values remain unbiased. Calculations like these help build the quantitative case to acquire large, fairly deep, precision velocity samples of stream stars.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Grillmair, C. J.0000-0003-4072-169X
Additional Information:© 2016 American Astronomical Society. Received 2016 June 19; revised 2016 August 3; accepted 2016 August 3; published 2016 October 18. This research was supported by CIFAR and NSERC Canada. An anonymous referee provided constructive criticism.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Canadian Institute for Advanced Research (CIFAR)UNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Subject Keywords:dark matter; galaxies: dwarf; Local Group
Issue or Number:2
Record Number:CaltechAUTHORS:20161018-115305461
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Official Citation:R. G. Carlberg and C. J. Grillmair 2016 ApJ 830 135
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:71224
Deposited By: Ruth Sustaita
Deposited On:18 Oct 2016 20:44
Last Modified:03 Oct 2019 16:05

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