Chinese scientists have captured the chemical and kinematic signals of the Milky Way bar resonance across a large spatial scale within the galaxy, addressing many limitations of previous studies that relied on Milky Way substructures to capture bar resonance signals. The research findings were recently published in The Astrophysical Journal Letters, with Sun Weixiang, a postdoctoral researcher at Beijing Normal University, as the first author of the paper.
Sun Weixiang explained that there exists a rotating bar or quadrupole bar within the Milky Way, and detecting the resonant signals of the Milky Way bar is crucial for constraining the fundamental properties of the galactic bar. However, previous detections of Milky Way bar resonance signals were limited to the peculiar local kinematic substructures in the vicinity of the Sun, which made it difficult to determine whether these peculiar local kinematic substructures were formed by bar resonances.
The study suggests the necessity of constructing properties that commonly exist across a larger disk area of the Milky Way to detect the resonant signals of the galactic bar, which will help further constrain the fundamental properties of the Milky Way bar.
Sun Weixiang stated, "Theoretically, whether the Milky Way has a rotating bar or a rotating quadrupole bar, the resonant signals of the Milky Way bar should exist in the chemical and kinematic characteristics within a larger disk area."
Sun Weixiang and his colleagues utilized data from more than 170,000 red giant stars provided by the Guo Shoujing Telescope (LAMOST) and the Apache Point Observatory Galactic Evolution Experiment (APOGEE), combined with astrometric data provided by the European Space Agency's Gaia space observatory. Through measurements of chemical properties, they discovered significant periodic oscillations in the vertical metallicity gradient of these red giant stars with changing Milky Way radius after removing the overall trend.
The study also found that the fitting results of the thin disk (old) and thick disk (young) exhibited distinctly different wave function forms, indicating the existence of two distinct resonance modes of the Milky Way.
"This achievement realizes the detection of Milky Way bar resonance signals from chemical and kinematic properties, laying the foundation for further research on the properties of the Milky Way bar," said Sun Weixiang.
Related Paper Information: https://doi.org/10.3847/2041-8213/ad3554
