Understanding the Velocity Distribution of the Galactic Bulge with APOGEE and Gaia
Zhou,Yingying1,2; Li,Zhao-Yu3,4; Simion,Iulia T.1; Shen,Juntai3,4; Mao,Shude5,6; Liu,Chao2,6; Jian,Mingjie7; Fernández-Trincado,José G.8
Source PublicationThe Astrophysical Journal
AbstractAbstract We revisit the stellar velocity distribution in the Galactic bulge/bar region with Apache Point Observatory Galactic Evolution Experiment DR16 and Gaia DR2, focusing in particular on the possible high-velocity (HV) peaks and their physical origin. We fit the velocity distributions with two different models, namely with Gauss–Hermite polynomials and Gaussian mixture models (GMMs). The result of the fit using Gauss–Hermite polynomials reveals a positive correlation between the mean velocity ( ) and the “skewness” (h3) of the velocity distribution, possibly caused by the Galactic bar. The n = 2 GMM fitting reveals a symmetric longitudinal trend of ∣μ2∣ and σ2 (the mean velocity and the standard deviation of the secondary component), which is inconsistent with the x2 orbital family predictions. Cold secondary peaks could be seen at ∣l∣ ~ 6°. However, with the additional tangential information from Gaia, we find that the HV stars in the bulge show similar patterns in the radial–tangential velocity distribution (VR–VT), regardless of the existence of a distinct cold HV peak. The observed VR–VT (or VGSR–μl) distributions are consistent with the predictions of a simple Milky Way bar model. The chemical abundances and ages inferred from ASPCAP and CANNON suggest that the HV stars in the bulge/bar are generally as old as, if not older than, the other stars in the bulge/bar region.
KeywordMilky Way dynamics Galactic bulge
WOS IDIOP:0004-637X-908-1-abd181
PublisherThe American Astronomical Society
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Document Type期刊论文
Corresponding AuthorShen,Juntai
Affiliation1.Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, People’s Republic of China
2.College of Astronomy and Space Sciences, University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing 100049, People’s Republic of China
3.Department of Astronomy, School of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People’s Republic of China,
4.Key Laboratory for Particle Astrophysics and Cosmology (MOE) / Shanghai Key Laboratory for Particle Physics and Cosmology, Shanghai 200240, People’s Republic of China
5.Department of Astronomy, Tsinghua University, Beijing 100084, People’s Republic of China
6.National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, People’s Republic of China
7.Department of Astronomy, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
8.Instituto de Astronomía y Ciencias Planetarias, Universidad de Atacama, Copayapu 485, Copiapó, Chile
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GB/T 7714
Zhou,Yingying,Li,Zhao-Yu,Simion,Iulia T.,et al. Understanding the Velocity Distribution of the Galactic Bulge with APOGEE and Gaia[J]. The Astrophysical Journal,2021,908(1).
APA Zhou,Yingying.,Li,Zhao-Yu.,Simion,Iulia T..,Shen,Juntai.,Mao,Shude.,...&Fernández-Trincado,José G..(2021).Understanding the Velocity Distribution of the Galactic Bulge with APOGEE and Gaia.The Astrophysical Journal,908(1).
MLA Zhou,Yingying,et al."Understanding the Velocity Distribution of the Galactic Bulge with APOGEE and Gaia".The Astrophysical Journal 908.1(2021).
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