The GALAH survey : stellar streams and how stellar velocity distributions vary with Galactic longitude, hemisphere, and metallicity

Alice C. Quillen, Gayandhi De Silva, Sanjib Sharma, Michael Hayden, Ken Freeman, Joss Bland-Hawthorn, Marusa Zerjal, Martin Asplund, Sven Buder, Valentina D'Orazi, Ly Duong, Janez Kos, Jane Lin, Karin Lind, Sarah Martell, Katharine Schlesinger, Jeffrey D. Simpson, Daniel B. Zucker, Tomaz Zwitter, Borja AnguianoDaniela Carollo, Luca Casagrande, Klemen Cotar, Peter L. Cottrell, Michael Ireland, Prajwal R. Kafle, Jonathan Horner, Geraint F. Lewis, David M. Nataf, Yuan-Sen Ting, Fred Watson, Rob Wittenmyer, Rosemary Wyse

Research output: Contribution to journalArticlepeer-review

Abstract

Using GALAH (GALactic Archaeology with HERMES) survey data of nearby stars, we look at how structure in the planar (u, v) velocity distribution depends on metallicity and on viewing direction within the Galaxy. In nearby stars with distance d less than or similar to 1 kpc, the Hercules stream is most strongly seen in higher metallicity stars [Fe/H] > 0.2. The Hercules stream peak v value depends on viewed galactic longitude, which we interpret as due to the gap between the stellar stream and more circular orbits being associated with a specific angular momentum value of about 16.40 km s(-1) kpc. The association of the gap with a particular angular momentum value supports a bar resonant model for the Hercules stream. Moving groups previously identified in Hipparcos (High Precision Parallax COllecting Satellite) observations are easiest to see in stars nearer than 250 pc, and their visibility and peak velocities in the velocity distributions depends on both viewing direction (galactic longitude and hemisphere) and metallicity. We infer that there is fine structure in local velocity distributions that varies over distances of a few hundred pc in the Galaxy.
Original languageEnglish
Pages (from-to)228-254
Number of pages27
JournalMonthly Notices of the Royal Astronomical Society
Volume478
Issue number1
DOIs
Publication statusPublished - 2018

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