{
  "abstract": "We present a Bayesian hierarchical forward model for mapping the local luminosity-density field from heterogeneous redshift surveys. By dividing the survey volume into angular cells and redshift shells, we model the observed galaxy distribution directly in apparent-magnitude and redshift space. This allows us to infer cell-level luminosity functions and densities while preserving each survey's unique selection function. Simultaneously, the ensemble of cells constrains the cosmic-mean luminosity function, its redshift evolution, and the hyperparameters describing cell-to-cell variation. We apply the framework to 2MRS, 6dFGS, and GAMA over $0.005<z<0.065$, combining wide sky coverage with deeper and fainter galaxy samples. The model successfully recovers global $J$-band luminosity-function parameters and a mean luminosity density consistent with previous low-redshift measurements. The inferred luminosity-density scatter decreases with volume, consistent with the cosmic-variance amplitude expected in a $Λ$CDM universe. Within the volume we probe, we find no evidence for a large coherent underdensity. Instead, the local Universe is broadly consistent with smooth evolution and cosmic variance. The nearest shell at $z \\simeq 0.01$ is the clearest exception, lying $\\simeq 0.12$~dex ($\\simeq 25\\%$) below the smooth global model, a $-2.6σ$ underdensity with a one-sided significance of $\\simeq 99.5\\%$. This framework offers a scalable architecture for mapping cosmic density fields with next-generation wide and deep surveys.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.36462",
  "author_total": 4,
  "authors": [
    {
      "name": "Aryan Bansal"
    },
    {
      "name": "Edward N. Taylor"
    },
    {
      "name": "Michelle Cluver"
    },
    {
      "name": "Matthew Colless"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/dwra00m9jkpdj.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.36462",
  "fulltext_url": null,
  "id": "dwra00m9jkpdj",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.36462",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.CO"
    ],
    [
      "arxiv",
      "astro-ph.GA"
    ],
    [
      "arxiv",
      "astro-ph.IM"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2609.36462",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-29",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/dwra00m9jkpdj.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:35:35Z",
      "native_id": "2609.36462",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.36462"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.CO",
      "subfield": "cosmology"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.GA",
      "subfield": "galaxies"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.IM",
      "subfield": "instrumentation-methods"
    }
  ],
  "title": "Everything Everywhere All At Once: A Hierarchical Framework for Mapping Anisotropies in the Local Universe",
  "title_text": "Everything Everywhere All At Once: A Hierarchical Framework for Mapping Anisotropies in the Local Universe",
  "type": "preprint",
  "updated_at": "2026-10-30T12:35:35Z",
  "url": "https://research.draconitic.com/paper/dwra00m9jkpdj",
  "venue": "arXiv",
  "versions": [
    {
      "doi": "10.1093/mnras/stag1867",
      "pid": "0y5eq3f6kxk0e",
      "relation": "published-as",
      "title": "Everything everywhere all at once: a hierarchical framework for mapping anisotropies in the local Universe",
      "venue": "Monthly Notices of the Royal Astronomical Society"
    }
  ]
}