Fundamental relations for the velocity dispersion of stars in the Milky Way

Sharma, Sanjib and Hayden, Michael R. and Bland-Hawthorn, Joss and Stello, Dennis and Buder, Sven and Zinn, Joel C. and Kallinger, Thomas and Asplund, Martin and de Silva, Gayandhi M. and D'Orazi, Valentina and Freeman, Ken and Kos, Janez and Lewis, Geraint F. and Lin, Jane and Lind, Karin and Martell, Sarah and Simpson, Jeffrey D. and Wittenmyer, Rob A. and Zucker, Daniel B. and Zwitter, Tomaz and Chen, Boquan and Cotar, Klemen and Esdaile, James and Hon, Marc and Horner, Jonathan and Huber, Daniel and Kafle, Prajwal R. and Khanna, Shourya and Ting, Yuan-Sen and Nataf, David M. and Nordlander, Thomas and Saadon, Mohd Hafiz Mohd and Tepper-Garcia, Thor and Tinney, C. G. and Traven, Gregor and Watson, Fred and Wright, Duncan and Wyse, Rosemary F. G. (2021) Fundamental relations for the velocity dispersion of stars in the Milky Way. Monthly Notices of the Royal Astronomical Society, 506. pp. 1761-1776. ISSN 0035-8711

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Abstract

We explore the fundamental relations governing the radial and vertical velocity dispersions of stars in the Milky Way, from combined studies of complementary surveys including GALAH, LAMOST, APOGEE, the NASA Kepler and K2 missions, and Gaia DR2. We find that different stellar samples, even though they target different tracer populations and employ a variety of age estimation techniques, follow the same set of fundamental relations. We provide the clearest evidence to date that, in addition to the well-known dependence on stellar age, the velocity dispersions of stars depend on orbital angular momentum Lz, metallicity and height above the plane |z|, and are well described by a multiplicatively separable functional form. The dispersions have a power-law dependence on age with exponents of 0.441±0.007 and 0.251±0.006 for σz and σR respectively, and the power law is valid even for the oldest stars. For the solar neighborhood stars, the apparent break in the power law for older stars, as seen in previous studies, is due to the anti-correlation of Lz with age. The dispersions decrease with increasing Lz until we reach the Sun's orbital angular momentum, after which σz increases (implying flaring in the outer disc) while σR flattens. For a given age, the dispersions increase with decreasing metallicity, suggesting that the dispersions increase with birth radius. The dispersions also increase linearly with |z|. The same set of relations that work in the solar neighborhood also work for stars between 3 < R/kpc < 20. Finally, the high-[α/Fe] stars follow the same relations as the low-[α/Fe] stars.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: C. 2021 The Author(s). Published version deposited in accordance with the copyright policy of the publisher.
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Astrophysics (1 Aug 2018 -)
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Astrophysics (1 Aug 2018 -)
Date Deposited: 28 Jul 2021 03:25
Last Modified: 20 Sep 2021 05:07
Uncontrolled Keywords: galaxies; disc; evolution; formation; kinematics and dynamics; astrophysics; astrophysics of galaxies
Fields of Research (2008): 02 Physical Sciences > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems
Fields of Research (2020): 51 PHYSICAL SCIENCES > 5101 Astronomical sciences > 510109 Stellar astronomy and planetary systems
Socio-Economic Objectives (2008): E Expanding Knowledge > 97 Expanding Knowledge > 970102 Expanding Knowledge in the Physical Sciences
Socio-Economic Objectives (2020): 28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280120 Expanding knowledge in the physical sciences
Identification Number or DOI: https://doi.org/10.1093/mnras/stab1086
URI: http://eprints.usq.edu.au/id/eprint/42814

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