{
  "abstract": "The Hubble tension motivates careful scrutiny of the redshift-independent distances underpinning the local distance ladder. Water megamasers afford a purely geometric distance from orbital dynamics in an accretion disc. For five of the six Megamaser Cosmology Project (MCP) galaxies, we present a Bayesian forward model that infers the angular-diameter distance and warped Keplerian disc parameters jointly from the very long baseline interferometry quasi-observables: maser spot positions, velocities, and accelerations. We then constrain $H_0$ from these distances and the host redshifts, including a physical distance prior, modelling the galaxy sample selection and testing a linear and a non-linear peculiar-velocity reconstruction. Accounting for peculiar velocities with the non-linear Manticore reconstruction, we infer $H_0 = 71.6 \\pm 3.7$ km/s/Mpc, where the uncertainty is statistical. Relative to ignoring peculiar velocities, the linear and non-linear reconstructions lower $H_0$ by $0.8$--$1.4$ and $1.6$--$2.1$ km/s/Mpc, respectively, whereas changing the selection variable alters it by less than $1$ km/s/Mpc. We analyse the sixth galaxy, NGC 4258, separately. Modelling its disc as eccentric and quadratically warped, we infer an angular-diameter distance of $7.558 \\pm 0.073$ (stat.) Mpc, within $0.13σ$ of the published maser distance.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.17684",
  "author_total": 2,
  "authors": [
    {
      "name": "Richard Stiskalek"
    },
    {
      "name": "Harry Desmond"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/7947zdmhdn656.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.17684",
  "fulltext_url": null,
  "id": "7947zdmhdn656",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.17684",
  "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.CO"
    ],
    [
      "arxiv",
      "astro-ph.GA"
    ],
    [
      "openalex",
      "3103|Cosmology and Gravitation Theories"
    ]
  ],
  "openalex": "W7213499639",
  "pdf_url": "https://arxiv.org/pdf/2609.17684",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-15",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/7947zdmhdn656.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:22:01Z",
      "native_id": "2609.17684",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.17684"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.CO",
      "subfield": "cosmology"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.GA",
      "subfield": "galaxies"
    }
  ],
  "title": "A reanalysis of the megamaser Hubble constant: from spot catalogues to peculiar velocities",
  "title_text": "A reanalysis of the megamaser Hubble constant: from spot catalogues to peculiar velocities",
  "type": "preprint",
  "updated_at": "2026-10-30T12:22:01Z",
  "url": "https://research.draconitic.com/paper/7947zdmhdn656",
  "venue": "arXiv",
  "versions": []
}