Measuring the vertical age structure of the Galactic disc using asteroseismology and SAGA

Abstract

The existence of a vertical age gradient in the Milky Way disc has been indirectly known for long. Here, we measure it directly for the first time with seismic ages, using red giants observed by Kepler. We use Stroemgren photometry to gauge the selection function of asteroseismic targets, and derive colour and magnitude limits where giants with measured oscillations are representative of the underlying population in the field. Limits in the 2MASS system are also derived. We lay out a method to assess and correct for target selection effects independent of Galaxy models. We find that low mass, i.e. old red giants dominate at increasing Galactic heights, whereas closer to the Galactic plane they exhibit a wide range of ages and metallicities. Parametrizing this as a vertical gradient returns approximately 4 Gyr/kpc for the disc we probe, although with a large dispersion of ages at all heights. The ages of stars show a smooth distribution over the last 10 Gyr, consistent with a mostly quiescent evolution for the Milky Way disc since a redshift of about 2. We also find a flat age-metallicity relation for disc stars. Finally, we show how to use secondary clump stars to estimate the present-day intrinsic metallicity spread, and suggest using their number count as a new proxy for tracing the ageing of the disc. This work highlights the power of asteroseismology for Galactic studies; however, we also emphasize the need for better constraints on stellar mass-loss, which is a major source of systematic age uncertainties in red giant stars.

MNRAS, accepted. SAGA website and data at http://www.mso.anu.edu.au/saga/data_access.html

References in corpus (17)

• The K2 Mission: Characterization and Early results
• Properties of galaxies reproduced by a hydrodynamic simulation
• New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey
• The rapid formation a large rotating disk galaxy three billion years after the Big Bang
• Present-day cosmic abundances. A comprehensive study of nearby early B-type stars and implications for stellar and Galactic evolution and interstellar dust models
• The Geneva-Copenhagen Survey of the Solar neighbourhood II. New uvby calibrations and rediscussion of stellar ages, the G dwarf problem, age-metallicity diagram, and heating mechanisms of the disk
• The APOKASC Catalog: An Asteroseismic and Spectroscopic Joint Survey of Targets in the Kepler Fields
• Radial mixing and the transition between the thick and thin Galactic discs
• Young [$\alpha$/Fe]-enhanced stars discovered by CoRoT and APOGEE: What is their origin?
• Constraining the thick disc formation scenario of the Milky Way
• Stroemgren survey for Asteroseismology and Galactic Archaeology: let the SAGA begin
• Mass loss on the red giant branch: the value and metallicity dependence of Reimers' η in globular clusters
• The ability of intermediate-band Stromgren photometry to correctly identify dwarf, subgiant, and giant stars and provide stellar metallicities and surface gravities
• Does SEGUE/SDSS indicate a dual Galactic halo?
• An empirical mass-loss law for Population II giants from the Spitzer-IRAC survey of Galactic globular clusters
• Hubble Space Telescope observations of the Kepler-field cluster NGC 6819. I. The bottom of the white dwarf cooling sequence
• The Galactic Stellar Disc

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