Dynamical heating across the Milky Way disc using APOGEE and Gaia

Journal Article · 29 August 2019 · Monthly Notices of the Royal Astronomical Society

DOI: https://doi.org/10.1093/mnras/stz1521 · OSTI ID:1559338

Mackereth, J. Ted  ^[1]; Bovy, Jo  ^[2]; Leung, Henry W.  ^[3]; Schiavon, Ricardo P. ^[4]; Trick, Wilma H. ^[5]; Chaplin, William J. ^[6]; Cunha, Katia ^[7]; Feuillet, Diane K. ^[8]; Majewski, Steven R. ^[9]; Martig, Marie ^[4]; Miglio, Andrea  ^[6]; Nidever, David ^[10]; Pinsonneault, Marc H. ^[11]; Aguirre, Victor Silva ^[12]; Sobeck, Jennifer ^[13]; Tayar, Jamie  ^[14]; Zasowski, Gail ^[15]

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1. Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool L3 5RF, UK, School of Astronomy and Astrophysics, University of Birmingham, Edgbaston, Birmimgham B15 2TT, UK
2. Department of Astronomy and Astrophysics, University of Toronto, 50 St George Street, Toronto, ON M5S 3H4, Canada, Dunlap Institute for Astronomy and Astrophysics, University of Toronto, 50 St George Street, Toronto, ON M5S 3H4, Canada
3. Department of Astronomy and Astrophysics, University of Toronto, 50 St George Street, Toronto, ON M5S 3H4, Canada
4. Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool L3 5RF, UK
5. Max-Planck-Insitut für Astrophysik, Karl-Schwarzschild-Str 1, D-85748 Garching b. München, Germany
6. School of Astronomy and Astrophysics, University of Birmingham, Edgbaston, Birmimgham B15 2TT, UK
7. Department of Astronomy, University of Arizona, Tucson, AZ 85719, USA, Observatório Nacional, São Cristóvão, Rio de Janeiro, RJ 20921-400, Brazil
8. Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany
9. Department of Astronomy, University of Virginia, Charlottesville, VA 22904, USA
10. National Optical Astronomy Observatories, Tucson, AZ 85719, USA
11. Department of Astronomy, The Ohio State University, Columbus, OH 43210, USA
12. Department of Physics and Astronomy, Stellar Astrophysics Centre, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark
13. Department of Astronomy Box 351580, University of Washington, Seattle, WA 98195-1580, USA
14. Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
15. Department of Physics & Astronomy, University of Utah, Salt Lake City, UT 84112, USA

Abstract The kinematics of the Milky Way disc as a function of age are well measured at the solar radius, but have not been studied over a wider range of Galactocentric radii. Here, we measure the kinematics of mono-age, mono-[Fe/H] populations in the low and high [α/Fe] discs between 4 ≲ R ≲ 13 kpc and |z| ≲ 2 kpc using 65 719 stars in common between APOGEE DR14 and Gaia DR2 for which we estimate ages using a Bayesian neural network model trained on asteroseismic ages. We determine the vertical and radial velocity dispersions, finding that the low and high [α/Fe] discs display markedly different age–velocity dispersion relations (AVRs) and shapes σz/σR. The high [α/Fe] disc has roughly flat AVRs and constant σz/σR = 0.64 ± 0.04, whereas the low [α/Fe] disc has large variations in this ratio that positively correlate with the mean orbital radius of the population at fixed age. The high [α/Fe] disc component’s flat AVRs and constant σz/σR clearly indicate an entirely different heating history. Outer disc populations also have flatter radial AVRs than those in the inner disc, likely due to the waning effect of spiral arms. Our detailed measurements of AVRs and σz/σR across the disc indicate that low [α/Fe], inner disc ($$R \lesssim 10\, \mathrm{kpc}$$) stellar populations are likely dynamically heated by both giant molecular clouds and spiral arms, while the observed trends for outer disc populations require a significant contribution from another heating mechanism such as satellite perturbations. We also find that outer disc populations have slightly positive mean vertical and radial velocities likely because they are part of the warped disc.

• Sponsoring Organization: USDOE
• OSTI ID: 1559338
• Journal Information: Monthly Notices of the Royal Astronomical Society, Journal Name: Monthly Notices of the Royal Astronomical Society Journal Issue: 1 Vol. 489; ISSN 0035-8711
• Publisher: Oxford University PressCopyright Statement
• Country of Publication: United Kingdom
• Language: English