The GALAH survey: temporal chemical enrichment of the galactic disc

Lin, Jane and Asplund, Martin and Ting, Yuan-Sen and Casagrande, Luca and Buder, Sven and Bland-Hawthorn, Joss and Casey, Andrew R. and de Silva, Gayandhi M. and D'Orazi, Valentina and Freeman, Ken C. and Kos, Janez and Lind, K. and Martell, Sarah L. and Sharma, Sanjib and Simpson, Jeffrey D. and Zwitter, Tomaz and Zucker, Daniel B. and Minchev, Ivan and Cotar, Klemen and Hayden, Michael and Horner, Jonti and Lewis, Geraint F. and Nordlander, Thomas and Wyse, Rosemary F.G. and Zerjal, Marusa (2020) The GALAH survey: temporal chemical enrichment of the galactic disc. Monthly Notices of the Royal Astronomical Society, 491 (2). pp. 2043-2056. ISSN 0035-8711

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Abstract

We present isochrone ages and initial bulk metallicities ([Fe/H]_{bulk}, by accounting for diffusion) of 163 722 stars from the GALAH Data Release 2, mainly composed of main-sequence turn-off stars and subgiants (7000 K> T_{ eff}> 4000 K and log g>3 dex). The local age- metallicity relationship (AMR) is nearly flat but with significant scatter at all ages; the scatter is even higher when considering the observed surface abundances. After correcting for selection effects, the AMR appears to have intrinsic structures indicative of two star formation events, which we speculate are connected to the thin and thick discs in the solar neighbourhood. We also present abundance ratio trends for 16 elements as a function of age, across different [Fe/H]_{bulk} bins. In general, we find the trends in terms of [X/Fe] versus age from our far larger sample to be compatible with studies based on small (∼100 stars) samples of solar twins, but we now extend them to both sub- and supersolar metallicities. The α-elements show differing behaviour: the hydrostatic α-elements O and Mg show a steady decline with time for all metallicities, while the explosive α-elements Si, Ca, and Ti are nearly constant during the thin-disc epoch (ages ≲ 12 Gyr). The s-process elements Y and Ba show increasing [X/Fe] with time while the r-process element Eu has the opposite trend, thus favouring a primary production from sources with a short time delay such as core-collapse supernovae over long-delay events such as neutron star mergers.


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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: 14 Sep 2020 05:15
Last Modified: 30 Sep 2020 03:20
Uncontrolled Keywords: stars: abundances; stars: fundamental parameters; solar; neighbourhood; Astrophysics - Solar and Stellar Astrophysics; Astrophysics - Astrophysics of Galaxies
Fields of Research (2008): 02 Physical Sciences > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems
Socio-Economic Objectives (2008): E Expanding Knowledge > 97 Expanding Knowledge > 970102 Expanding Knowledge in the Physical Sciences
Identification Number or DOI: https://doi.org/10.1093/mnras/stz3048
URI: http://eprints.usq.edu.au/id/eprint/39337

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