{
  "id": "2011.14065",
  "version": "v1",
  "published": "2020-11-28T04:07:26.000Z",
  "updated": "2020-11-28T04:07:26.000Z",
  "title": "Understanding the velocity distribution of the Galactic Bulge with APOGEE and Gaia",
  "authors": [
    "Yingying Zhou",
    "Zhao-Yu Li",
    "Iulia Simion",
    "Juntai Shen",
    "Shude Mao",
    "Chao Liu",
    "Mingjie Jian",
    "José. G. Fernández-Trincado"
  ],
  "comment": "17 pages,13 figures",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "We revisit the stellar velocity distribution in the Galactic bulge/bar region with APOGEE DR16 and {\\it 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 polynomial and Gaussian mixture model (GMM). The result of the fit using Gauss-Hermite polynomials reveals a positive correlation between the mean velocity ($\\bar{V}$) and the \"skewness\" ($h_{3}$) of the velocity distribution, possibly caused by the Galactic bar. The $n=2$ GMM fitting reveals a symmetric longitudinal trend of $|\\mu_{2}|$ and $\\sigma_{2}$ (the mean velocity and the standard deviation of the secondary component), which is inconsistent to the $x_{2}$ orbital family predictions. Cold secondary peaks could be seen at $|l|\\sim6^\\circ$. However, with the additional tangential information from {\\it Gaia}, we find that the HV stars in the bulge show similar patterns in the radial-tangential velocity distribution ($V_{\\rm R}-V_{\\rm T}$), regardless of the existence of a distinct cold HV peak. The observed $V_{\\rm R}-V_{\\rm T}$ (or $V_{\\rm GSR}-\\mu_{l}$) distributions are consistent with the predictions of a simple MW 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.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2020-11-28T04:07:26.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "galactic bulge",
      "bulge/bar region",
      "mean velocity",
      "gauss-hermite polynomial",
      "hv stars"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 17,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}