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

Quillen, Alice C. and de Silva, Gayandhi and Sharma, Sanjib and Hayden, Michael and Freeman, Ken and Bland-Hawthorn, Joss and Zerjal, Marusa and Asplund, Martin and Buder, Sven and D'Orazi, Valentina and Duong, Ly and Kos, Janez and Lin, Jane and Lind, Karin and Martell, Sarah and Schlesinger, Katharine and Simpson, Jeffrey D. and Zucker, Daniel B. and Zwitter, Tomaz and Anguiano, Borja and Carollo, Daniela and Casagrande, Luca and Cotar, Klemen and Cottrell, Peter L. and Ireland, Michael and Kafle, Prajwal R. and Horner, Jonathan and Lewis, Geraint F. and Nataf, David M. and Ting, Yuan-Sen and Watson, Fred and Wittenmyer, Rob and Wyse, Rosemary (2018) The GALAH survey: stellar streams and how stellar velocity distributions vary with Galactic longitude, hemisphere, and metallicity. Monthly Notices of the Royal Astronomical Society, 478 (12). pp. 228-254. ISSN 0035-8711

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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 ≲ 1 kpc, the Hercules stream is most strongly seen in higher metallicity stars [Fe/H] &gt; 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 1640 km s<SUP>-1</SUP> 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.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Published version deposited in accordance with the copyright policy of the publisher.
Faculty/School / Institute/Centre: Current - Faculty of Health, Engineering and Sciences - School of Agricultural, Computational and Environmental Sciences
Date Deposited: 15 Feb 2019 03:24
Last Modified: 04 Mar 2019 04:09
Uncontrolled Keywords: galaxies; evolution; kinematics and dynamics; astrophysics; astrophysics of galaxies
Fields of Research : 02 Physical Sciences > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems
Identification Number or DOI: 10.1093/mnras/sty865

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