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Metallicity gradient of the thick disc progenitor at high redshift

Kawata, Daisuke; Prieto, Carlos Allende; Brook, Chris B.; Casagrande, Luca; Ciucă, Ioana; Gibson, Brad K.; Grand, Robert J. J.; Hayden, Michael R.; Hunt, Jason A. S.

Authors

Daisuke Kawata

Carlos Allende Prieto

Chris B. Brook

Luca Casagrande

Ioana Ciucă

Robert J. J. Grand

Michael R. Hayden

Jason A. S. Hunt



Abstract

© 2017 The Authors. We have developed a novel Markov Chain Monte Carlo chemical 'painting' technique to explore possible radial and vertical metallicity gradients for the thick disc progenitor. In our analysis, we match an N-body simulation to the data from the Apache Point Observatory Galactic Evolution Experiment survey.We assume that the thick disc has a constant scaleheight and has completed its formation at an early epoch, after which time radial mixing of its stars has taken place. Under these assumptions, we find that the initial radial metallicity gradient of the thick disc progenitor should not be negative, but either flat or even positive, to explain the current negative vertical metallicity gradient of the thick disc. Our study suggests that the thick disc was built-up in an inside-out and upside-down fashion, and older, smaller and thicker populations are more metal poor. In this case, star-forming discs at different epochs of the thick disc formation are allowed to have different radial metallicity gradients, including a negative one, which helps to explain a variety of slopes observed in high-redshift disc galaxies. This scenario helps to explain the positive slope of the metallicity-rotation velocity relation observed for the Galactic thick disc. On the other hand, radial mixing flattens the slope of an existing gradient.

Journal Article Type Article
Publication Date Jan 1, 2018
Journal Monthly notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Oxford University Press (OUP)
Peer Reviewed Peer Reviewed
Volume 473
Issue 1
Pages 867-878
APA6 Citation Kawata, D., Prieto, C. A., Brook, C. B., Casagrande, L., Ciucă, I., Gibson, B. K., …Hunt, J. A. S. (2018). Metallicity gradient of the thick disc progenitor at high redshift. Monthly notices, containing papers, abstracts of papers, and reports of the proceedings of the Society, 473(1), 867-878. https://doi.org/10.1093/mnras/stx2464
DOI https://doi.org/10.1093/mnras/stx2464
Keywords Methods: numerical; Galaxy: disc; Galaxy: kinematics and dynamics
Publisher URL https://academic.oup.com/mnras/article/473/1/867/4222624
Related Public URLs http://discovery.ucl.ac.uk/1561746/1/Kawata_Metallicity%20Gradient%20of%20the%20Thick%20Disc%20Progenitor%20at%20High%20Redshift.pdf
Copyright Statement This article has been accepted for publication in MNRAS ©: 2018 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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Copyright Statement
This article has been accepted for publication in MNRAS ©: 2018 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.



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