Journal article
The K2-HERMES Survey: age and metallicity of the thick disc
Monthly notices of the Royal Astronomical Society, Vol.490(4), pp.5335-5352
12/01/2019
DOI: 10.1093/mnras/stz2861
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 oldmetal-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 [alpha/Fe] elemental abundances from the GALAH survey indicate a mean metallicity of log (Z/Z(circle dot)) = -0.16 for the thick disc. Here Z is the effective solar-scaled metallicity, which is a function of [Fe/H] and [alpha/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 alpha-enhanced thick disc.
Details
- Title: Subtitle
- The K2-HERMES Survey: age and metallicity of the thick disc
- Creators
- Sanjib Sharma - University of SydneyDennis Stello - UNSW SydneyJoss Bland-HawthornMichael R. Hayden - University of SydneyJoel C. Zinn - The Ohio State UniversityThomas Kallinger - University of ViennaMarc Hon - UNSW SydneyMartin Asplund - ARC Centre of Excellence for All-sky AstrophysicsSven Buder - Max Planck Institute for AstronomyGayandhi M. De Silva - Macquarie UniversityValentina D'Orazi - INAF, Vicolo Osservatorio 5, I-35122 Padua, PD, ItalyKen Freeman - Australian National UniversityJanez Kos - University of LjubljanaGeraint F. Lewis - University of SydneyJane Lin - Australian National UniversityKarin Lind - Uppsala UniversitySarah Martell - UNSW SydneyJeffrey D. Simpson - UNSW SydneyRob A. Wittenmyer - University of Southern QueenslandDaniel B. Zucker - Macquarie UniversityTomaz Zwitter - University of LjubljanaTimothy R. Bedding - University of SydneyBoquan Chen - University of SydneyKlemen Cotar - University of LjubljanaJames Esdaile - UNSW SydneyJonathan Horner - University of Southern QueenslandDaniel Huber - Search for Extraterrestrial IntelligencePrajwal R. Kafle - International Centre for Radio Astronomy ResearchShourya Khanna - University of SydneyTanda Li - University of SydneyYuan-Sen Ting - Institute for Advanced StudyDavid M. Nataf - Johns Hopkins UniversityThomas Nordlander - ARC Centre of Excellence for All-sky AstrophysicsMohd Hafiz Mohd Saadon - UNSW SydneyGregor Traven - University of LjubljanaDuncan Wright - University of Southern QueenslandRosemary F. G. Wyse - Johns Hopkins University
- Resource Type
- Journal article
- Publication Details
- Monthly notices of the Royal Astronomical Society, Vol.490(4), pp.5335-5352
- DOI
- 10.1093/mnras/stz2861
- ISSN
- 0035-8711
- eISSN
- 1365-2966
- Language
- English
- Date published
- 12/01/2019
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984701731102771
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