{
  "id": "2305.04991",
  "version": "v1",
  "published": "2023-05-08T18:54:31.000Z",
  "updated": "2023-05-08T18:54:31.000Z",
  "title": "First observations of warm and cold methanol in Class 0/I proto-brown dwarfs",
  "authors": [
    "B. Riaz",
    "W. -F. Thi",
    "M. N. Machida"
  ],
  "comment": "Accepted in MNRAS",
  "categories": [
    "astro-ph.GA",
    "astro-ph.SR"
  ],
  "abstract": "We present results from the first molecular line survey to search for the fundamental complex organic molecule, methanol (CH$_{3}$OH), in 14 Class 0/I proto-brown dwarfs (proto-BDs). IRAM 30-m observations over the frequency range of 92-116 GHz and 213-280 GHz have revealed emission in 14 CH$_{3}$OH transition lines, at upper state energy level, E$_{upper}\\sim$7-49 K, and critical densities, $n_{crit}$ of 10$^{5}$ to 10$^{9}$ cm$^{-3}$. The most commonly detected lines are at E$_{upper} <$ 20 K, while 11 proto-BDs also show emission in the higher excitation lines at E$_{upper}\\sim$21-49 K and $n_{crit}\\sim$10$^{5}$ to 10$^{8}$ cm$^{-3}$. In comparison with the brown dwarf formation models, the high excitation lines likely probe the warm ($\\sim$25-50 K) corino region at $\\sim$10-50 au in the proto-BDs, while the low-excitation lines trace the cold ($<$ 20 K) gas at $\\sim$50-150 au. The column density for the cold component is an order of magnitude higher than the warm component. The CH$_{3}$OH ortho-to-para ratios range between $\\sim$0.3-2.3. The volume-averaged CH$_{3}$OH column densities show a rise with decreasing bolometric luminosity among the proto-BDs, with the median column density higher by a factor of $\\sim$3 compared to low-mass protostars. Emission in high-excitation (E$_{upper}>$ 25 K) CH$_{3}$OH lines together with the model predictions suggest that a warm corino is present in $\\sim$78\\% of the proto-BDs in our sample. The remaining show evidence of only the cold component, possibly due to the absence of a strong, high-velocity jet that can stir up the warm gas around it.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2023-05-08T18:54:31.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "proto-brown dwarfs",
      "cold methanol",
      "first observations",
      "fundamental complex organic molecule",
      "first molecular line survey"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}