{
  "id": "2408.09252",
  "version": "v1",
  "published": "2024-08-17T16:51:01.000Z",
  "updated": "2024-08-17T16:51:01.000Z",
  "title": "Parabolic-like Trend in SiO Ratios throughout the Central Molecular Zone: Possible Signature of a Past Nuclear Activity in the Galactic Center",
  "authors": [
    "Shunya Takekawa",
    "Tomoharu Oka",
    "Shiho Tsujimoto",
    "Hiroki Yokozuka",
    "Nanase Harada",
    "Miyuki Kaneko",
    "Rei Enokiya",
    "Yuhei Iwata"
  ],
  "comment": "9 pages, 4 figures, accepted for publication in the Astrophysical Journal Letters",
  "doi": "10.3847/2041-8213/ad6c51",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "We report the discovery of a characteristic trend in the intensity ratios of SiO emissions across the Central Molecular Zone (CMZ) of our Galaxy. Using the Nobeyama Radio Observatory 45-m telescope, we conducted large-scale, high-sensitivity imaging observations in molecular lines including SiO $J$=2$-$1 and CS $J$=2$-$1. By identifying SiO-emitting clouds and examining their intensity ratios relative to the other molecular lines, we unveiled a parabolic-like trend showing lower ratios near the Galactic nucleus, Sgr A$^*$, with gradual increases toward the edges of the CMZ. This pattern suggests a possible outburst of the nucleus within the last $\\sim 10^5$ yr, which may have propagated through the entire CMZ with strong shocks. Alternatively, the observed trend may also be attributed to the destruction of small dust grains by high-energy photons. Our results can potentially lead to a new perspective on the history of nuclear activity and its impact on the surrounding molecular environment.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2024-08-17T16:51:01.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "central molecular zone",
      "past nuclear activity",
      "sio ratios throughout",
      "parabolic-like trend",
      "galactic center"
    ],
    "tags": [
      "journal article"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 9,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}