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Title: A measurement of the distance to the Galactic centre using the kinematics of bar stars

Abstract

ABSTRACT The distance to the Galactic centre R0 is a fundamental parameter for understanding the Milky Way, because all observations of our Galaxy are made from our heliocentric reference point. The uncertainty in R0 limits our knowledge of many aspects of the Milky Way, including its total mass and the relative mass of its major components, and any orbital parameters of stars employed in chemo-dynamical analyses. While measurements of R0 have been improving over a century, measurements in the past few years from a variety of methods still find a wide range of R0 being somewhere within 8.0 to $$8.5\, \mathrm{kpc}$$. The most precise measurements to date have to assume that Sgr A* is at rest at the Galactic centre, which may not be the case. In this paper, we use maps of the kinematics of stars in the Galactic bar derived from APOGEE DR17 and Gaia EDR3 data augmented with spectrophotometric distances from the astroNN neural-network method. These maps clearly display the minimum in the rotational velocity vT and the quadrupolar signature in radial velocity vR expected for stars orbiting in a bar. From the minimum in vT, we measure $$R_0 = 8.23\pm 0.12\, \mathrm{kpc}$$. We validate our measurement using realistic N-body simulations of the Milky Way. We further measure the pattern speed of the bar to be $$\Omega _\mathrm{bar} = 40.08\pm 1.78\, \mathrm{km\, s}^{-1}\,\mathrm{kpc}^{-1}$$. Because the bar forms out of the disc, its centre is manifestly the barycentre of the bar+disc system and our measurement is therefore one of the most robust and accurate measurements of R0 to date.

Authors:
ORCiD logo; ORCiD logo; ORCiD logo; ORCiD logo; ;
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1906405
Resource Type:
Published Article
Journal Name:
Monthly Notices of the Royal Astronomical Society
Additional Journal Information:
Journal Name: Monthly Notices of the Royal Astronomical Society Journal Volume: 519 Journal Issue: 1; Journal ID: ISSN 0035-8711
Publisher:
Oxford University Press
Country of Publication:
United Kingdom
Language:
English

Citation Formats

Leung, Henry W., Bovy, Jo, Mackereth, J. Ted, Hunt, Jason A. S., Lane, Richard R., and Wilson, John C. A measurement of the distance to the Galactic centre using the kinematics of bar stars. United Kingdom: N. p., 2022. Web. doi:10.1093/mnras/stac3529.
Leung, Henry W., Bovy, Jo, Mackereth, J. Ted, Hunt, Jason A. S., Lane, Richard R., & Wilson, John C. A measurement of the distance to the Galactic centre using the kinematics of bar stars. United Kingdom. https://doi.org/10.1093/mnras/stac3529
Leung, Henry W., Bovy, Jo, Mackereth, J. Ted, Hunt, Jason A. S., Lane, Richard R., and Wilson, John C. Tue . "A measurement of the distance to the Galactic centre using the kinematics of bar stars". United Kingdom. https://doi.org/10.1093/mnras/stac3529.
@article{osti_1906405,
title = {A measurement of the distance to the Galactic centre using the kinematics of bar stars},
author = {Leung, Henry W. and Bovy, Jo and Mackereth, J. Ted and Hunt, Jason A. S. and Lane, Richard R. and Wilson, John C.},
abstractNote = {ABSTRACT The distance to the Galactic centre R0 is a fundamental parameter for understanding the Milky Way, because all observations of our Galaxy are made from our heliocentric reference point. The uncertainty in R0 limits our knowledge of many aspects of the Milky Way, including its total mass and the relative mass of its major components, and any orbital parameters of stars employed in chemo-dynamical analyses. While measurements of R0 have been improving over a century, measurements in the past few years from a variety of methods still find a wide range of R0 being somewhere within 8.0 to $8.5\, \mathrm{kpc}$. The most precise measurements to date have to assume that Sgr A* is at rest at the Galactic centre, which may not be the case. In this paper, we use maps of the kinematics of stars in the Galactic bar derived from APOGEE DR17 and Gaia EDR3 data augmented with spectrophotometric distances from the astroNN neural-network method. These maps clearly display the minimum in the rotational velocity vT and the quadrupolar signature in radial velocity vR expected for stars orbiting in a bar. From the minimum in vT, we measure $R_0 = 8.23\pm 0.12\, \mathrm{kpc}$. We validate our measurement using realistic N-body simulations of the Milky Way. We further measure the pattern speed of the bar to be $\Omega _\mathrm{bar} = 40.08\pm 1.78\, \mathrm{km\, s}^{-1}\,\mathrm{kpc}^{-1}$. Because the bar forms out of the disc, its centre is manifestly the barycentre of the bar+disc system and our measurement is therefore one of the most robust and accurate measurements of R0 to date.},
doi = {10.1093/mnras/stac3529},
journal = {Monthly Notices of the Royal Astronomical Society},
number = 1,
volume = 519,
place = {United Kingdom},
year = {Tue Dec 06 00:00:00 EST 2022},
month = {Tue Dec 06 00:00:00 EST 2022}
}

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https://doi.org/10.1093/mnras/stac3529

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