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Young stars as tracers of a barred-spiral Milky Way

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Title: Young stars as tracers of a barred-spiral Milky Way
Authors: Pettitt, Alex R. Browse this author
Ragan, Sarah E. Browse this author
Smith, Martin C. Browse this author
Keywords: hydrodynamics
ISM: structure
Galaxy: kinematics and dynamics
Galaxy: structure
galaxies: spiral
Issue Date: Jan-2020
Publisher: Oxford University Press
Journal Title: Monthly notices of the royal astronomical society
Volume: 491
Issue: 2
Start Page: 2162
End Page: 2179
Publisher DOI: 10.1093/mnras/stz3155
Abstract: Identifying the structure of our Galaxy has always been fraught with difficulties, and while modern surveys continue to make progress building a map of the Milky Way, there is still much to understand. The arm and bar features are important drivers in shaping the interstellar medium (ISM), but their exact nature and influence still require attention. We present results of smoothed particle hydrodynamic simulations of gas in the Milky Way including star formation, stellar feedback, and ISM cooling, when exposed to different arm and bar features, with the aim of better understanding how well newly formed stars trace out the underlying structure of the Galaxy. The bar is given a faster pattern speed than the arms, resulting in a complex, time-dependent morphology and star formation. Interarm branches and spurs are easily influenced by the bar, especially in the two-armed spiral models where there is a wide region of resonance overlap in the disc. As the bar overtakes the spiral arms it induces small boosts in star formation and enhances spiral features, which occur at regularly spaced beat-like intervals. The locations of star formation events are similar to those seen in observational data, and do not show a perfect 1:1 correspondence with the underlying spiral potential, though arm tangencies are generally well traced by young stars. Stellar velocity fields from the newly formed stars are compared to data from Gaia DR2, showing that the spiral and bar features can reproduce many of the non-axisymmetric features seen in the data. A simple analytical model is used to show many of these feature are a natural response of gas to rigidly rotating spiral and bar potentials.
Rights: This article has been accepted for publication in Monthly notices of the royal astronomical society ©: 2020 Published by Oxford University Press on behalf of The Royal Astronomical Society. All rights reserved.
Type: article
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