THE STELLAR POPULATION STRUCTURE OF THE GALACTIC DISK

By Jo Bovy, Hans-Walter Rix, Edward F. Schlafly, D. Nidever, J. Holtzman, M. Shetrone, Timothy C. Beers. 2015

137 citations recorded by the source corpus.

The spatial structure of stellar populations with different chemical abundances in the Milky Way (MW) contains a wealth of information on Galactic evolution over cosmic time. We use data on 14,699 red-clump stars from the APOGEE survey, covering , to determine the structure of mono-abundance populations (MAPs)—stars in narrow bins in and —accounting for the complex effects of the APOGEE selection function and the spatially variable dust obscuration. We determine that all MAPs with enhanced are centrally concentrated and are well-described as exponentials with a scale length of over the whole radial range of the disk. We discover that the surface-density profiles of low- MAPs are complex: they do not monotonically decrease outwards, but rather display a peak radius ranging from to at low . The extensive radial coverage of the data allows us to measure radial trends in the thickness of each MAP. While high- MAPs have constant scale heights, low- MAPs flare. We confirm, now with high-precision abundances, previous results that each MAP contains only a single vertical scale height and that low- , low- and high- , high- MAPs have intermediate ( ) scale heights that smoothly bridge the traditional thin- and thick-disk divide. That the high- , thick disk components do not flare is strong evidence against their thickness being caused by radial migration. The correspondence between the radial structure and chemical-enrichment age of stellar populations is clear confirmation of the inside-out growth of galactic disks. The details of these relations will constrain the variety of physical conditions under which stars form throughout the MW disk.

Subfields: Astronomy and Astrophysics, Instrumentation

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Citations in the corpus

Yule-Simpson’s paradox in Galactic Archaeology (2019, background): “Another example of a trend that can be related to the Galaxy’s past is the variation of disk thickness with Galactocentric radius (or flaring, e.g., Kazantzidis et al. 2008; Bovy et al. 2016; Kawata et al. 2017; Wang et al. 2018; BlandHawthorn & Gerhard 2016).”
Confirming chemical clocks: asteroseismic age dissection of the Milky Way disc(s) (2017, background): “…selected sequences span a similar range of values in Zmax as a function of age, consistent with both populations having similar scale heights and thus not being representative of a geometric decomposition of the disc into a thin and a thick component (as found by e.g. Bovy et al. 2012, 2016).”
The age–metallicity structure of the Milky Way disc using APOGEE (2017, methodology): “…at the equilibrium point of chemical evolution for a given population (where the consumption of gas and its dilution are balanced, as discussed in Bovy et al. 2016b), then one might consider that such a broadening would occur if stars that formed near the equilibrium point migrated inwards and…”
THE RELATIONSHIP BETWEEN MONO-ABUNDANCE AND MONO-AGE STELLAR POPULATIONS IN THE MILKY WAY DISK (2016, background): “The recent analyses of the APOGEE red-clump (RC) sample by Bovy et al. 2016 (hereafter B16) suggest that the structure of groups of stars in narrow bins of [Fe/H] and [α/Fe], known as mono-abundance populations (MAPs), is different for stars with high- and low[α/Fe] values.”
Impacts of a flaring star-forming disc and stellar radial mixing on the vertical metallicity gradient (2016, methodology): “Fitting the different populations of the APOGEE data with parametrised radial and vertical density profiles, Bovy et al. (2016) also showed the compact thick disc population and flaring thin disc populations.”
The structure and dynamical evolution of the stellar disc of a simulated Milky Way-mass galaxy (2016, background): “The disk flaring broadly agrees with observations in the MW stellar disk (e.g. Momany et al. 2006; Kalberla et al. 2014; López-Corredoira & Molgó 2014; Bovy et al. 2016).”
Vertical disc heating in Milky Way-sized galaxies in a cosmological context (2015, background): “These results highlight that upside-down disc formation (Bird et al. 2013; Stinson et al. 2013b; Bovy et al. 2015) occurs on some level ubiquitously, which has important implications for thick disc formation.”
A RADIAL AGE GRADIENT IN THE GEOMETRICALLY THICK DISK OF THE MILKY WAY (2016, background): “Indeed, the α-rich thick disk is centrally concentrated with a short scale length of about 2 kpc (Bensby et al. 2011; Bovy et al. 2012, 2016; Cheng et al. 2012b), and very few α-rich stars are found in the outer disk of the Milky Way (Nidever et al. 2014; Hayden et al. 2015).”
StarHorse : a Bayesian tool for determining stellar masses, ages, distances, and extinctions for field stars (2017, methodology): “…for mapping the chemical and kinematical properties of Galactic populations using large stellar surveys (e.g., Boeche et al. 2013, 2014; Anders et al. 2014; Recio-Blanco et al. 2014; Nidever et al. 2014; Mikolaitis et al. 2014; Hayden et al. 2015; Carlin et al. 2015; Bovy et al. 2016).”