{
  "id": "2208.13497",
  "version": "v1",
  "published": "2022-08-29T11:03:03.000Z",
  "updated": "2022-08-29T11:03:03.000Z",
  "title": "An MCMC Approach to the Three-dimensional Structure of the Milky Way Bulge using OGLE-IV $δ$ Scuti Stars",
  "authors": [
    "Mami Deka",
    "Sukanta Deb",
    "Kerdaris Kurbah"
  ],
  "comment": "11 pages, 5 figures, accepted for publication in MNRAS",
  "doi": "10.1093/mnras/stac1596",
  "categories": [
    "astro-ph.GA",
    "astro-ph.SR"
  ],
  "abstract": "We present an analysis of high latitude $\\delta$ Scuti stars ($\\left|b\\right|> 1^{\\circ}$) in the Galactic bulge region ($-8^{\\circ}.3< l<9^{\\circ}.4$) using a clean sample of the photometric data of $7,440$ stars recently released by the OGLE-IV project. The geometrical parameters of the bulge are determined based on Maximum Likelihood (ML) analysis in five-dimensional parameter space. More refined values of these parameters as well as their uncertainties are obtained from a fully Bayesian Markov Chain Monte Carlo (MCMC) analysis. Approximating the bulge as an ellipsoid, the distribution of the number density of stars as a function of Galacto-centric distance has been modelled using three distribution functions: two Exponential ($\\rm E_{1},\\rm E_{2}$) types and one Gaussian ($\\rm G$) type. Based on the AIC and BIC values, the exponential model $\\rm E_{1}$ is chosen as the best statistical model for the parameter values obtained from the MCMC analysis. The MCMC analysis yields the following results: the mean distance to the Galactic center (GC) is found to be $R_{0}=8.034\\pm0.012_{\\rm stat}\\pm0.586_{\\rm sys}$ kpc; the bulge $\\delta$ Scuti distribution has a triaxial shape with normalized ($a\\equiv1$) axes ratios ($a:b:c$) as $1.000\\pm 0.005:0.348\\pm0.002:0.421\\pm0.002$. Here $a$ is the semi-major axis lying in the Galactic plane and pointing towards us; $b$ and $c$ are the two semi-minor axes, the former lying in the Galactic plane and the later perpendicular to it. Smaller values of $b$ as compared to $a$ obtained for Galacto-centric distances $R\\ge 2.0$~kpc indicate the presence of a bar-like structure of the bulge with a bar angle of $22^{\\circ}.006\\pm2^{\\circ}.078$.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2022-08-29T11:03:03.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "milky way bulge",
      "scuti stars",
      "mcmc approach",
      "three-dimensional structure",
      "bayesian markov chain monte carlo"
    ],
    "tags": [
      "journal article"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 11,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}