{
  "abstract": "Context. The ionisation balance in molecular clouds is regulated by several ionising sources, including cosmic rays, X-rays, and ultraviolet radiation. Their relative importance depends on the local physical conditions and on the shielding column density. Aims. Our goal is to quantify the contribution of the large-scale diffuse X-ray radiation field to ionisation in molecular clouds in the absence of strong local X-ray sources, such as young stars, and to assess its significance relative to Galactic cosmic rays. Methods. We used measurements of diffuse X-ray emission from the first eROSITA all-sky survey to estimate the depth-dependent X-ray ionisation rate in molecular clouds across different Galactic environments. We considered both the observed diffuse field and a deabsorbed field obtained by correcting for foreground Galactic attenuation using HI4PI line-of-sight column densities in a pixel-by-pixel framework. Results. Diffuse Galactic X-rays are unlikely to dominate the ionisation balance in well-shielded molecular gas (NH > 5 × 1021cm−2), where cosmic rays remain the primary ionising agent. At low column densities, the deabsorbed diffuse X-ray field produces an ionisation rate of ζX ∼ 10−18s−1 at NH ∼ 1019cm−2, remaining below the lower end of the Galactic cosmic ray ionisation rate (∼10−17s−1). The X-ray contribution decreases rapidly with increasing shielding, falling to ζX ∼ 10−19s−1 by NH ∼ 1021cm−2 and to ζX ∼ 5 × 10−21s−1 by NH ∼ 1022cm−2. Diffuse X-ray may therefore contribute to the thermal and chemical structure of low-extinction material and should be considered when interpreting ionisation tracers in diffuse or cloud-envelope environments.",
  "abstract_shown": true,
  "affiliations": [
    "Max Planck Institute for Extraterrestrial Physics",
    "Physics Department, Technion – Israel Institute of Technology",
    "Faculty of Physics, University of Duisburg-Essen",
    "INAF–Osservatorio Astrofisico di Arcetri"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 8,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "Makarenko E. I.",
      "orcid": "0000-0002-9694-1790"
    },
    {
      "affs": [
        0
      ],
      "name": "Ivlev A. V.",
      "orcid": "0000-0002-1590-1018"
    },
    {
      "affs": [
        1
      ],
      "name": "Bialy S.",
      "orcid": "0000-0002-0404-003X"
    },
    {
      "affs": [
        0
      ],
      "name": "Zheng X.",
      "orcid": "0000-0001-7386-4609"
    },
    {
      "affs": [
        2
      ],
      "name": "Gaches B. A. L.",
      "orcid": "0000-0003-4224-6829"
    },
    {
      "affs": [
        0
      ],
      "name": "Caselli P.",
      "orcid": "0000-0003-1481-7911"
    },
    {
      "affs": [
        3
      ],
      "name": "Padovani M.",
      "orcid": "0000-0003-2303-0096"
    },
    {
      "affs": [
        0
      ],
      "name": "Yeung M. C. H.",
      "orcid": "0000-0002-5697-0001"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/5zjye0jvpdedf.bib",
  "cited_by": 0,
  "doi": "10.1051/0004-6361/202662444",
  "fulltext_url": "https://www.aanda.org/articles/aa/full_html/2026/10/aa62444-26/aa62444-26.html",
  "id": "5zjye0jvpdedf",
  "issns": [
    "0004-6361",
    "1432-0746"
  ],
  "landing_url": "https://doi.org/10.1051/0004-6361/202662444",
  "language": "en",
  "licence": "CC-BY",
  "licence_label": "CC BY",
  "licence_source": "journal",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "lcc",
      "QB1-991"
    ],
    [
      "openalex",
      "3103|Astrophysics and Star Formation Studies"
    ]
  ],
  "openalex": "W7207829713",
  "pdf_url": null,
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-27",
  "publisher": "EDP Sciences",
  "ris": "https://research.draconitic.com/paper/5zjye0jvpdedf.ris",
  "sources": [
    {
      "first_seen": "2026-10-31T14:21:55Z",
      "native_id": "12e709d9c6e340e797db769e947c74d7",
      "source": "doaj",
      "url": "https://doi.org/10.1051/0004-6361/202662444"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "openalex:3103|Astrophysics and Star Formation Studies",
      "subfield": "stellar"
    }
  ],
  "title": "Can diffuse X-rays be important in driving photoionisation in molecular clouds?",
  "title_text": "Can diffuse X-rays be important in driving photoionisation in molecular clouds?",
  "type": "peer-reviewed",
  "updated_at": "2026-10-31T14:21:55Z",
  "url": "https://research.draconitic.com/paper/5zjye0jvpdedf",
  "venue": "Astronomy & Astrophysics",
  "versions": []
}