Dynamically constraining the length of the Milky Way bar

Abstract

We present a novel 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 $\approx$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 $\approx$3.5 kpc. We find the Milky Way's trapped bar orbits extend out to only $\approx$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.

15 pages, 8 figures, 2 tables, accepted to MNRAS, comments welcome

References in corpus (32)

• Array Programming with NumPy
• The 2.5 m Telescope of the Sloan Digital Sky Survey
• Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties
• galpy: A Python Library for Galactic Dynamics
• Dynamics of Barred Galaxies
• Dynamical modelling of the Galactic bulge and bar: the Milky Way's bar pattern speed, stellar, and dark matter mass distribution
• The Structure of the Milky Way's Bar Outside the Bulge
• The Apache Point Observatory Galactic Evolution Experiment (APOGEE) Spectrographs
• Target Selection for the SDSS-IV APOGEE-2 Survey
• The APOGEE Data Release 16 Spectral Line List
• K-Band Observations of Boxy Bulges. I. Morphology and Surface Brightness Profiles
• ARGOS II: The Galactic Bulge Survey
• Tracing the long bar with red-clump giants
• Kinematics at the Edge of the Galactic Bulge: Evidence for Cylindrical Rotation
• The Long Bar in the Milky Way. Corroboration of an old hypothesis
• Milky Way mass galaxies with X-shaped bulges are not rare in the local Universe
• The long Galactic bar as seen by UKIDSS Galactic Plane Survey
• Tree-ring structure of Galactic bar resonance
• The Pristine Inner Galaxy Survey (PIGS) I: Tracing the kinematics of metal-poor stars in the Galactic bulge
• Revisiting the tension between fast bars and the $\Lambda$CDM paradigm
• A direct measurement of the distance to the Galactic center using the kinematics of bar stars
• Variations in the width, density, and direction of the Palomar 5 tidal tails
• The Bulge Radial Velocity Assay for RR Lyrae stars (BRAVA-RR) DR2: a Bimodal Bulge?
• Exploring the Sgr-Milky-Way-disc interaction using high resolution N-body simulations
• The COMBS Survey -- II. Distinguishing the Metal-Poor Bulge from the Halo Interlopers
• Did Sgr cause the vertical waves in the solar neighbourhood?
• Applying Schwarzschild's orbit superposition method to barred or non-barred disc galaxies
• Separatrix Divergence of Stellar Streams in Galactic Potentials
• The Coupling of Galactic Dark Matter Halos with Stellar Bars
• Orbital classification in an N-body bar
• Frequencies, chaos and resonances: a study of orbital parameters of nearby thick disc and halo stars
• A barred Milky Way surrogate from an N-body simulation

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