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  1. OA@INAF
  2. PRODOTTI RICERCA INAF
  3. 1 CONTRIBUTI IN RIVISTE (Journal articles)
  4. 1.01 Articoli in rivista
Please use this identifier to cite or link to this item: http://hdl.handle.net/20.500.12386/28723
Title: The K2-HERMES Survey: age and metallicity of the thick disc
Authors: Sharma, Sanjib
Stello, Dennis
Bland-Hawthorn, Joss
Hayden, Michael R.
Zinn, Joel C.
Kallinger, Thomas
Hon, Marc
Asplund, Martin
Buder, Sven
De Silva, Gayandhi M.
D'ORAZI, VALENTINA 
Freeman, Ken
Kos, Janez
Lewis, Geraint F.
Lin, Jane
Lind, Karin
Martell, Sarah
Simpson, Jeffrey D.
Wittenmyer, Rob A.
Zucker, Daniel B.
Zwitter, Tomaz
Bedding, Timothy R.
Chen, Boquan
Cotar, Klemen
Esdaile, James
Horner, Jonathan
Huber, Daniel
Kafle, Prajwal R.
Khanna, Shourya
Li, Tanda
Ting, Yuan-Sen
Nataf, David M.
Nordlander, Thomas
Saadon, Mohd Hafiz Mohd
Traven, Gregor
Wright, Duncan
Wyse, Rosemary F. G.
Issue Date: 2019
Journal: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 
Number: 490
Issue: 4
First Page: 5335
Abstract: Asteroseismology is a promising tool to study Galactic structure and evolution because it can probe the ages of stars. Earlier attempts comparing seismic data from the Kepler satellite with predictions from Galaxy models found that the models predicted more low-mass stars compared to the observed distribution of masses. It was unclear if the mismatch was due to inaccuracies in the Galactic models, or the unknown aspects of the selection function of the stars. Using new data from the K2 mission, which has a well-defined selection function, we find that an old metal-poor thick disc, as used in previous Galactic models, is incompatible with the asteroseismic information. We use an importance-sampling framework, which takes the selection function into account, to fit for the metallicities of a population synthesis model using spectroscopic data. We show that spectroscopic measurements of [Fe/H] and [α/Fe] elemental abundances from the GALAH survey indicate a mean metallicity of log (Z/Z<SUB>☉</SUB>) = -0.16 for the thick disc. Here Z is the effective solar-scaled metallicity, which is a function of [Fe/H] and [α/Fe]. With the revised disc metallicities, for the first time, the theoretically predicted distribution of seismic masses show excellent agreement with the observed distribution of masses. This indirectly verifies that the asteroseismic mass scaling relation is good to within five per cent. Assuming the asteroseismic scaling relations are correct, we estimate the mean age of the thick disc to be about 10 Gyr, in agreement with the traditional idea of an old α-enhanced thick disc.
URI: http://hdl.handle.net/20.500.12386/28723
URL: https://academic.oup.com/mnras/article/490/4/5335/5586605
ISSN: 0035-8711
DOI: 10.1093/mnras/stz2861
Bibcode ADS: 2019MNRAS.490.5335S
Fulltext: open
Appears in Collections:1.01 Articoli in rivista

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