{
  "abstract": "We report CO and HI studies of molecular and atomic gas toward the TeV gamma-ray source HESS J1646$-$458, widely considered to be associated with the young massive cluster Westerlund 1 (Wd1). We found that molecular clouds at $V_\\mathrm{LSR} \\sim$$-32$ km s$^{-1}$ coincide with arc-like structures seen at 8 $μ$m, likely illuminated by strong FUV radiation from Wd1. $^{12}$CO($J$ = 3-2) emission at the same velocity reveals a cavity-like structure with an expansion velocity of $\\sim$$5$ km s$^{-1}$ toward the central region of Wd1, suggesting a recently formed wind-blown bubble driven by the cluster. We also identify a complementary spatial distribution between the $V_\\mathrm{LSR} \\sim$$-55$ and $\\sim$$-32$ km s$^{-1}$ clouds, connected by an intermediate-velocity component at $V_\\mathrm{LSR} \\sim$$-44$ km s$^{-1}$. These characteristics are consistent with signatures of triggered star formation through a cloud-cloud collision and imply that both clouds are physically associated with Wd1. On larger scales, the total interstellar proton column density at $V_\\mathrm{LSR}$ $\\sim$$-36$-$-23$ km s$^{-1}$ shows a moderate spatial correspondence with the TeV gamma-ray shell. Together with this correlation, a substantial gas mass of $\\sim$$1.6 \\times 10^6$ $M_\\odot$, and the absence of bright synchrotron X-rays, the TeV gamma-ray emission surrounding Wd1 is consistent with the hadronic origin. The present finding allows us to calculate the total energy of accelerated cosmic-ray protons to be $\\sim$$6 \\times 10^{49}$ erg.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2605.25467",
  "author_total": 24,
  "authors": [
    {
      "name": "H. Sano"
    },
    {
      "name": "Y. Fukui"
    },
    {
      "name": "S. Fujimori"
    },
    {
      "name": "T. Murase"
    },
    {
      "name": "R. Z. E. Alsaberi"
    },
    {
      "name": "M. D. Filipović"
    },
    {
      "name": "G. Rowell"
    },
    {
      "name": "M. Aruga"
    },
    {
      "name": "Y. Asano"
    },
    {
      "name": "R. G. Bhuvana"
    },
    {
      "name": "F. Demachi"
    },
    {
      "name": "S. Einecke"
    },
    {
      "name": "N. Fukaya"
    },
    {
      "name": "R. Hamada"
    },
    {
      "name": "H. Inoue"
    },
    {
      "name": "T. Kamazaki"
    },
    {
      "name": "S. Lazarević"
    },
    {
      "name": "T. Minamidani"
    },
    {
      "name": "Z. J. Smeaton"
    },
    {
      "name": "H. Sudou"
    },
    {
      "name": "K. Tachihara"
    },
    {
      "name": "H. Takaba"
    },
    {
      "name": "K. Tsuge"
    },
    {
      "name": "R. I. Yamada"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/88yekvbed76b9.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2605.25467",
  "fulltext_url": null,
  "id": "88yekvbed76b9",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2605.25467",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.GA"
    ],
    [
      "arxiv",
      "astro-ph.HE"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2605.25467",
  "pmcid": null,
  "pmid": null,
  "published": "2026-05-25",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/88yekvbed76b9.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:17:22Z",
      "native_id": "2605.25467",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2605.25467"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.GA",
      "subfield": "galaxies"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.HE",
      "subfield": "high-energy-astrophysics"
    }
  ],
  "title": "Discovery of Molecular and Atomic Gas associated with HESS J1646-458 (Westerlund 1): Spatial TeV Gamma-Ray and Interstellar Proton Correspondence",
  "title_text": "Discovery of Molecular and Atomic Gas associated with HESS J1646-458 (Westerlund 1): Spatial TeV Gamma-Ray and Interstellar Proton Correspondence",
  "type": "preprint",
  "updated_at": "2026-10-30T12:17:22Z",
  "url": "https://research.draconitic.com/paper/88yekvbed76b9",
  "venue": "arXiv",
  "versions": [
    {
      "doi": "10.3847/1538-4357/ae6337",
      "pid": null,
      "relation": "published-as",
      "title": null,
      "venue": null
    }
  ]
}