Journal article
The GALAH survey: properties of the Galactic disc(s) in the solar neighbourhood
Monthly notices of the Royal Astronomical Society, Vol.476(4), pp.5216-5232
06/01/2018
DOI: 10.1093/mnras/sty525
Abstract
Using data from the GALAH pilot survey, we determine properties of the Galactic thin and thick discs near the solar neighbourhood. The data cover a small range of Galactocentric radius (7.9 less than or similar to R-GC less than or similar to 9.5 kpc), but extend up to 4 kpc in height from the Galactic plane, and several kpc in the direction of Galactic anti-rotation (at longitude 260 degrees <= l <= 280 degrees). This allows us to reliably measure the vertical density and abundance profiles of the chemically and kinematically defined 'thick' and 'thin' discs of the Galaxy. The thin disc (low-alpha population) exhibits a steep negative vertical metallicity gradient, at d[M/H]/dz = -0.18 +/- 0.01 dex kpc(-1), which is broadly consistent with previous studies. In contrast, its vertical alpha-abundance profile is almost flat, with a gradient of d[alpha/M]/dz = 0.008 +/- 0.002 dex kpc(-1). The steep vertical metallicity gradient of the low-a population is in agreement with models where radial migration has a major role in the evolution of the thin disc. The thick disc (high-alpha population) has a weaker vertical metallicity gradient d[M/H]/dz = -0.058 +/- 0.003 dex kpc(-1). The aabundance of the thick disc is nearly constant with height, d[alpha/M]/dz = 0.007 +/- 0.002 dex kpc(-1). The negative gradient in metallicity and the small gradient in [alpha/M] indicate that the high-alpha population experienced a settling phase, but also formed prior to the onset of major Type I alpha supernova enrichment. We explore the implications of the distinct alpha-enrichments and narrow [alpha/M] range of the sub-populations in the context of thick disc formation.
Details
- Title: Subtitle
- The GALAH survey: properties of the Galactic disc(s) in the solar neighbourhood
- Creators
- L. Duong - Australian National UniversityK. C. Freeman - Australian National UniversityM. Asplund - Australian National UniversityL. Casagrande - Australian National UniversityS. Buder - Max Planck Institute for AstronomyK. Lind - Max Planck Institute for AstronomyM. Ness - Max Planck Institute for AstronomyJ. Bland-Hawthorn - University of SydneyG. M. De Silva - University of SydneyV. D'Orazi - INAF, Osservatorio Astron Padova, Vicolo Osservatorio 5, I-35122 Padua, ItalyJ. Kos - University of SydneyG. F. Lewis - University of SydneyJ. Lin - Australian National UniversityS. L. Martell - UNSW SydneyK. Schlesinger - Australian National UniversityS. Sharma - University of SydneyJ. D. Simpson - Australian Astronomical ObservatoryD. B. Zucker - Macquarie UniversityT. Zwitter - University of LjubljanaB. Anguiano - Macquarie UniversityG. S. Da Costa - Australian National UniversityE. Hyde - Western Sydney UniversityJ. Horner - University of Southern QueenslandP. R. Kafle - University of Western AustraliaD. M. Nataf - Australian National UniversityW. Reid - Macquarie UniversityD. Stello - University of SydneyY. -S. Ting - Australian National UniversityR. F. G. Wyse - Johns Hopkins University
- Resource Type
- Journal article
- Publication Details
- Monthly notices of the Royal Astronomical Society, Vol.476(4), pp.5216-5232
- Publisher
- Oxford Univ Press
- DOI
- 10.1093/mnras/sty525
- ISSN
- 0035-8711
- eISSN
- 1365-2966
- Number of pages
- 17
- Grant note
- Allan C. and Dorothy H. Davis Fellowship DP160103747 / ARC grant; Australian Research Council National Science Foundation; National Science Foundation (NSF) National Aeronautics and Space Administration; National Aeronautics & Space Administration (NASA) FT1400147 / Australian Research Council Future Fellowship; Australian Research Council DP150100250; FT160100402 / Australian Research Council P1-0188 / Slovenian Research Agency; Slovenian Research Agency - Slovenia Munich Institute for Astro- and Particle Physics (MIAPP) of the DFG cluster of excellence 'Origin and Structure of the Universe' FT160100402 / Australian Research Council FL110100012 / Australian Government through ARC Laureate Fellowship
- Language
- English
- Date published
- 06/01/2018
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984701828502771
Metrics
1 Record Views