The GALAH survey: chemodynamics of the solar neighbourhood

Hayden, Michael R. and Bland-Hawthorn, Joss and Sharma, Sanjib and Freeman, Ken and Kos, Janez and Buder, Sven and Anguiano, Borja and Asplund, Martin and Chen, Boquan and de Silva, Gayandhi M. and Khanna, Shourya and Lin, Jane and Horner, Jonathan and Martell, Sarah and Ting, Yuan-Sen and Wyse, Rosemary and Zucker, Daniel and Zwitter, Tomaz (2020) The GALAH survey: chemodynamics of the solar neighbourhood. Monthly Notices of the Royal Astronomical Society, 493 (2). pp. 2952-2964. ISSN 0035-8711

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We present the chemodynamic structure of the solar neighbourhood using 55 652 stars within a 500 pc volume around the Sun observed by GALAH and with astrometric parameters from Gaia DR2. We measure the velocity dispersion for all three components (vertical, radial, and tangential) and find that it varies smoothly with [Fe/H] and [α/Fe] for each component. The vertical component is especially clean, with σ _{v_z} increasing from a low of 10 km s<SUP>-1</SUP> at solar [α/Fe] and [Fe/H] to a high of more than 50 km s<SUP>-1</SUP> for more metal-poor and [α/Fe] enhanced populations. We find no evidence of a large decrease in the velocity dispersion of the highest [α/Fe] populations as claimed in surveys prior to Gaia DR2. The eccentricity distribution for local stars varies most strongly as a function of [α/Fe], where stars with [α/Fe] &lt; 0.1 dex having generally circular orbits (e &lt; 0.15), while the median eccentricity increases rapidly for more [α/Fe] enhanced stellar populations up to e ∼ 0.35. These [α/Fe] enhanced populations have guiding radii consistent with origins in the inner Galaxy. Of the stars with metallicities much higher than the local interstellar medium ([Fe/H] &gt; 0.1 dex), we find that the majority have e &lt; 0.2 and are likely observed in the solar neighbourhood through churning/migration rather than blurring effects, as the epicyclic motion for these stars is not large enough to reach the radii at which they were likely born based on their metallicity.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Access to Published version in accordance with the copyright policy of the publisher.
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Astrophysics (1 Aug 2018 -)
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Astrophysics (1 Aug 2018 -)
Date Deposited: 15 Sep 2020 01:20
Last Modified: 27 Jul 2022 02:02
Uncontrolled Keywords: Galaxy: abundances; Galaxy: kinematics and dynamics; Galaxy: stellar; content; Galaxy: structure; Astrophysics - Astrophysics of Galaxies
Fields of Research (2008): 02 Physical Sciences > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems
Fields of Research (2020): 51 PHYSICAL SCIENCES > 5101 Astronomical sciences > 510109 Stellar astronomy and planetary systems
Socio-Economic Objectives (2008): E Expanding Knowledge > 97 Expanding Knowledge > 970102 Expanding Knowledge in the Physical Sciences
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