Dynamically constraining the length of the Milky way bar

Madeline Lucey, Sarah Pearson, Jason A.~S. Hunt, Keith Hawkins, Melissa Ness, Michael S. Petersen, Adrian M. Price-Whelan, Martin D. Weinberg

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)

Abstract

We present a no v el method for constraining the length of the Galactic bar using 6D phase-space information to directly integrate
orbits. We define a pseudo-length for the Galactic bar, named R Freq , based on the maximal extent of trapped bar orbits. We find
the R Freq measured from orbits is consistent with the R Freq of the assumed potential only when the length of the bar and pattern
speed of said potential is similar to the model from which the initial phase-space coordinates of the orbits are derived. Therefore,
one can measure the model’s or the Milky Way’s bar length from 6D phase-space coordinates by determining which assumed
potential leads to a self-consistent measured R Freq . When we apply this method to ≈210 000 stars in APOGEE DR17 and Gaia
eDR3 data, we find a consistent result only for potential models with a dynamical bar length of ≈3.5 kpc. We find the Milky
Way’s trapped bar orbits extend out to only ≈3.5 kpc, but there is also an overdensity of stars at the end of the bar out to 4.8 kpc
which could be related to an attached spiral arm. We also find that the measured orbital structure of the bar is strongly dependent
on the properties of the assumed potential.
Original languageEnglish
Pages (from-to)4779-4792
Number of pages14
Journalmnras
Volume520
Issue number3
DOIs
Publication statusPublished - 6 Feb 2023
Externally publishedYes

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