TY - JOUR
T1 - The age-metallicity structure of the Milky Way disc using APOGEE
AU - Mackereth, J. Ted
AU - Bovy, Jo
AU - Schiavon, Ricardo P.
AU - Zasowski, Gail
AU - Cunha, Katia
AU - Frinchaboy, Peter M.
AU - García Perez, Ana E.
AU - Hayden, Michael R.
AU - Holtzman, Jon
AU - Majewski, Steven R.
AU - Mészáros, Szabolcs
AU - Nidever, David L.
AU - Pinsonneault, Marc
AU - Shetrone, Matthew D.
N1 - Funding Information:
It is a pleasure to thank MarieMartig for helpful comments and discussion, and also for providing the catalogue of ages for APOGEE DR12 in digital format. We also thank Ivan Minchev, Misha Haywood and Paola Di Matteo for insightful discussion and comments that improved the clarity of the manuscript. The analysis and plots in the paper used IPYTHON, and packages in the SCIPY ecosystem (Jones et al. 2001; Hunter 2007; Perez & Granger 2007; van der Walt, Colbert & Varoquaux 2011). JTM is funded by a Science and Technology Facilities Council (UK) studentship and was hosted at the University of Toronto for a short period while completing this work. JB received support from the Natural Sciences and Engineering Research Council of Canada, an Alfred P. Sloan Fellowship and from the Simons Foundation. SM has been supported by the Premium Postdoctoral Research Program of the Hungarian Academy of Sciences, and by the Hungarian NKFI Grants K-119517 of the Hungarian National Research, Development and Innovation Office. Funding for SDSS-III was provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation and the U.S. Department of Energy Office of Science. The SDSS-III web site is http://www.sdss3.org/.
Publisher Copyright:
© 2018 The Author(s).
PY - 2017
Y1 - 2017
N2 - The measurement of the structure of stellar populations in the Milky Way disc places fundamental constraints on models of galaxy formation and evolution. Previously, the disc's structure has been studied in terms of populations defined geometrically and/or chemically, but a decomposition based on stellar ages provides a more direct connection to the history of the disc, and stronger constraint on theory. Here, we use positions, abundances and ages for 31 244 red giant branch stars from the Sloan Digital Sky Survey (SDSS)-APOGEE survey, spanning 3 < Rgc < 15 kpc, to dissect the disc into mono-age and mono-[Fe/H] populations at low and high [α/Fe]. For each population, with Δage < 2 Gyr and Δ[Fe/H] < 0.1 dex, we measure the structure and surface-mass density contribution. We find that low [α/Fe] mono-age populations are fit well by a broken exponential, which increases to a peak radius and decreases thereafter. We show that this profile becomes broader with age, interpreted here as a new signal of disc heating and radial migration. High [α/Fe] populations are well fit as single exponentials within the radial range considered, with an average scalelength of 1.9 ± 0.1 kpc. We find that the relative contribution of high to low [α/Fe] populations at R0 is fΣ = 18 per cent ± 5 per cent; high [α/Fe] contributes most of the mass at old ages, and low [α/Fe] at young ages. The low and high [α/Fe] populations overlap in age at intermediate [Fe/H], although both contribute mass at R0 across the full range of [Fe/H]. The mass-weighted scaleheight hZ distribution is a smoothly declining exponential function. High [α/Fe] populations are thicker than low [α/Fe], and the average hZ increases steadily with age, between 200 and 600 pc.
AB - The measurement of the structure of stellar populations in the Milky Way disc places fundamental constraints on models of galaxy formation and evolution. Previously, the disc's structure has been studied in terms of populations defined geometrically and/or chemically, but a decomposition based on stellar ages provides a more direct connection to the history of the disc, and stronger constraint on theory. Here, we use positions, abundances and ages for 31 244 red giant branch stars from the Sloan Digital Sky Survey (SDSS)-APOGEE survey, spanning 3 < Rgc < 15 kpc, to dissect the disc into mono-age and mono-[Fe/H] populations at low and high [α/Fe]. For each population, with Δage < 2 Gyr and Δ[Fe/H] < 0.1 dex, we measure the structure and surface-mass density contribution. We find that low [α/Fe] mono-age populations are fit well by a broken exponential, which increases to a peak radius and decreases thereafter. We show that this profile becomes broader with age, interpreted here as a new signal of disc heating and radial migration. High [α/Fe] populations are well fit as single exponentials within the radial range considered, with an average scalelength of 1.9 ± 0.1 kpc. We find that the relative contribution of high to low [α/Fe] populations at R0 is fΣ = 18 per cent ± 5 per cent; high [α/Fe] contributes most of the mass at old ages, and low [α/Fe] at young ages. The low and high [α/Fe] populations overlap in age at intermediate [Fe/H], although both contribute mass at R0 across the full range of [Fe/H]. The mass-weighted scaleheight hZ distribution is a smoothly declining exponential function. High [α/Fe] populations are thicker than low [α/Fe], and the average hZ increases steadily with age, between 200 and 600 pc.
KW - Galaxy: disc
KW - Galaxy: evolution
KW - Galaxy: formation
KW - Galaxy: fundamental parameters
KW - Galaxy: structure
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U2 - 10.1093/MNRAS/STX1774
DO - 10.1093/MNRAS/STX1774
M3 - Article
AN - SCOPUS:85040251379
SN - 0035-8711
VL - 471
SP - 3057
EP - 3078
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 3
ER -