{
  "id": "2412.05692",
  "version": "v1",
  "published": "2024-12-07T16:40:38.000Z",
  "updated": "2024-12-07T16:40:38.000Z",
  "title": "Diffuse Ionized Gas in the Anti-center of the Milky Way",
  "authors": [
    "Shiming Wen",
    "Wei Zhang",
    "Lin Ma",
    "Yunning Zhao",
    "Man I. Lam",
    "Chaojian Wu",
    "Juanjuan Ren",
    "Jianjun Chen",
    "Yuzhong Wu",
    "Guozhen Hu",
    "Yonghui Hou",
    "Yongheng Zhao",
    "Hong Wu"
  ],
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "Using data from the LAMOST Medium-Resolution Spectroscopic Survey of Nebulae, we create a sample of 17,821 diffuse ionized gas (DIG) spectra in the anti-center region of the Milky Way, by excluding fibers in the directions of H II regions and supernova remnants. We then analyze the radial and vertical distributions of three line ratios ([N II]/H$\\alpha$, [S II]/H$\\alpha$, and [S II]/[N II]), as well as the oxygen abundance. [N II]/H$\\alpha$ and [S II]/H$\\alpha$ do not exhibit a consistent, monotonic decrease with increasing Galactocentric distance (R$_{gal}$). Instead, they show enhancement within the interarm region, positioned between the Local Arm and the Perseus Arm. [S II]/[N II] has a radial gradient of 0.1415 $\\pm$ 0.0646 kpc$^{-1}$ for the inner disk (8.34 $ < R_{gal} < $ 9.65 kpc), and remains nearly flat for the outer disk ($R_{gal} > $ 9.65 kpc). In the vertical direction, [N II]/H$\\alpha$, [S II]/H$\\alpha$, and [S II]/[N II] increase with increasing Galactic disk height ($|z|$) in both southern and northern disks. Based on the N2S2H$\\alpha$ method, which combines [S II]/[N II] and [N II]/H$\\alpha$, we estimate the oxygen abundance. The oxygen abundance exhibits a consistent radial gradient with R$_{gal}$, featuring a slope of -0.0559 $\\pm$ 0.0209 dex kpc$^{-1}$ for the inner disk and a similar slope of -0.0429 $\\pm$ 0.0599 dex kpc$^{-1}$ for the outer disk. A single linear fitting to the entire disk yields a slope of -0.0317 $\\pm$ 0.0124 dex kpc$^{-1}$. In the vertical direction, the oxygen abundance decreases with increasing $|z|$ in both southern and northern disks.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2024-12-07T16:40:38.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "diffuse ionized gas",
      "milky way",
      "oxygen abundance",
      "dex kpc",
      "anti-center"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}