{
  "abstract": "We report a direct measurement of the 21-cm signal from neutral hydrogen (Hi) via the intensity mapping technique at redshift z = 0.42 through its power spectrum at cosmological scales 0.095 h Mpc−1 < k < 0.245 h Mpc−1. We analyse intensity maps observed in the frequency range 971.2 MHz < ν < 1023.6 MHz during the 2021 observational campaign of the MeerKAT Large Area Synoptic Survey (MeerKLASS) spanning an area of approximately 236 °2. Capitalising on the depth of this survey, we divide the data set into multiple observationally independent subsets. After performing blind contaminant separation independently on each subset, we exploit internal cross-correlations to suppress the instrumental noise plateau and isolate the cosmological signal from residual systematics. Although the subsets’ auto-spectra show the presence of excess power that we deem linked to still unresolved systematics, the cross-spectra measurements satisfactorily pass a battery of null and robustness tests. We introduce a multi-subset formalism to infer the amplitude of the Hi auto-spectrum from our internal cross-spectra measurements while marginalising the potential signal loss that occurs during data processing, reaching a detection with signal-to-noise ratio of 6.2. We constrain the clustering amplitude of the signal in terms of the Hi cosmic abundance and its linear bias, measuring 103 ΩHibHi = $1.271{_{-0.598}^{+1.080}}$. This direct measurement marks a milestone in demonstrating the effectiveness of the Hi intensity mapping technique for future surveys with the SKA Observatory, of which MeerKAT is a precursor.",
  "abstract_shown": true,
  "affiliations": [
    "Dipartimento di Fisica, Università degli Studi di Milano , via G. Celoria 16, 20133 Milano ,",
    "INFN - Istituto Nazionale di Fisica Nucleare, Sezione di Milano , via G. Celoria 16, 20133 Milano ,",
    "INAF – Istituto Nazionale di Astrofisica, Osservatorio Astrofisico di Brera-Merate , via Brera 28, 20121 Milano ,",
    "Dipartimento di Fisica, Università degli Studi di Torino , via P. Giuria 1, 10125 Torino ,",
    "Instituto de Física de Cantabria (IFCA), CSIC-Univ. de Cantabria , Avda. de los Castros s/n, E-39005 Santander ,",
    "Jodrell Bank Centre for Astrophysics, Department of Physics, and Astronomy, The University of Manchester , Manchester M13 9PL ,",
    "Department of Physics & Astronomy, University of the Western Cape , Robert Sobukwe Road, Cape Town 7535 ,",
    "INFN - Istituto Nazionale di Fisica Nucleare, Sezione di Torino , via P. Giuria 1, 10125 Torino ,",
    "INAF - Istituto Nazionale di Astrofisica, Osservatorio Astrofisico di Torino , 10025 Pino Torinese ,",
    "INAF – Istituto Nazionale di Astrofisica, Osservatorio Astronomico di Trieste , Via G.B. Tiepolo 11, 34131 Trieste ,",
    "IFPU – Institute for Fundamental Physics of the Universe , Via Beirut 2, 34151 Trieste ,",
    "Institute for Astronomy, The University of Edinburgh, Royal Observatory , Edinburgh EH9 3HJ ,",
    "Institute of Cosmology & Gravitation, University of Portsmouth , Dennis Sciama Building, Portsmouth, PO1 3FX ,",
    "Instituto de Astrofísica e Ciências do Espaço , Universidade do Porto CAUP, 4150-762 Porto ,",
    "Departamento de Física e Astronomia, Faculdade de Ciências , Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto ,",
    "State Key Laboratory of Radio Astronomy and Technology, National Astronomical Observatories , Chinese Academy of Sciences, Beijing 100101 ,",
    "Institute of Astrophysics, University of Cambridge , Madingley Road, CB3 0HA",
    "Department of Physics, College of Sciences, Northeastern University , Wenhua Road, Shenyang 11089 ,",
    "South African Radio Astronomy Observatory (SARAO) , Liesbeek House, Cape Town, 7700 ,",
    "Observatoire de la Côte d’Azur, Laboratoire Lagrange , Bd de l’Observatoire, CS 34229, 06304 Nice cedex 4 ,",
    "State Key Laboratory of Radio Astronomy and Technology, Shanghai Astronomical Observatory , CAS, 80 Nandan Road, Shanghai 200030 ,"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 19,
  "authors": [
    {
      "name": "MeerKLASS Collaboration"
    },
    {
      "affs": [
        0,
        1,
        2,
        3
      ],
      "name": "Matilde Barberi-Squarotti",
      "orcid": "0009-0007-8964-5807"
    },
    {
      "affs": [
        4
      ],
      "name": "José L Bernal"
    },
    {
      "affs": [
        5,
        6
      ],
      "name": "Philip Bull",
      "orcid": "0000-0001-5668-3101"
    },
    {
      "affs": [
        3,
        7,
        8,
        6
      ],
      "name": "Stefano Camera",
      "orcid": "0000-0003-3399-3574"
    },
    {
      "affs": [
        9,
        10
      ],
      "name": "Isabella P Carucci",
      "orcid": "0000-0001-5287-0065"
    },
    {
      "affs": [
        11
      ],
      "name": "Zhaoting Chen",
      "orcid": "0000-0002-4965-8239"
    },
    {
      "affs": [
        12,
        5
      ],
      "name": "Steven Cunnington"
    },
    {
      "affs": [
        6
      ],
      "name": "Brandon N Engelbrecht"
    },
    {
      "affs": [
        6,
        13,
        14
      ],
      "name": "José Fonseca",
      "orcid": "0000-0003-0549-1614"
    },
    {
      "affs": [
        5
      ],
      "name": "Keith Grainge"
    },
    {
      "affs": [
        15,
        6
      ],
      "name": "Wenkai Hu",
      "orcid": "0000-0002-3108-5591"
    },
    {
      "affs": [
        16,
        6
      ],
      "name": "Melis O Irfan"
    },
    {
      "affs": [
        17,
        6
      ],
      "name": "Yichao Li"
    },
    {
      "affs": [
        6,
        18
      ],
      "name": "Mário G Santos",
      "orcid": "0000-0003-3892-3073"
    },
    {
      "affs": [
        19,
        6
      ],
      "name": "Marta Spinelli",
      "orcid": "0000-0003-0148-3254"
    },
    {
      "affs": [
        20,
        6
      ],
      "name": "Jingying Wang"
    },
    {
      "affs": [
        6,
        5
      ],
      "name": "Amadeus Witzemann"
    },
    {
      "affs": [
        5
      ],
      "name": "Laura Wolz"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/00p5g7vh9z05g.bib",
  "cited_by": 0,
  "doi": "10.1093/mnras/stag1911",
  "fulltext_url": null,
  "id": "00p5g7vh9z05g",
  "issns": [
    "0035-8711",
    "1365-2966"
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  "licence_label": "CC BY 4.0",
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  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
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  "pmcid": null,
  "pmid": null,
  "published": "2026-11-03",
  "publisher": "Oxford University Press (OUP)",
  "ris": "https://research.draconitic.com/paper/00p5g7vh9z05g.ris",
  "sources": [
    {
      "first_seen": "2026-11-04T12:20:55Z",
      "native_id": "10.1093/mnras/stag1911",
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      "url": "https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stag1911/9011414"
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  "subjects": [
    {
      "field": "astronomy",
      "origin": "journal-openalex:3103|Stellar, planetary, and galactic studies",
      "subfield": "stellar"
    }
  ],
  "title": "Hi intensity mapping with MeerKAT: A measurement of the 21-cm auto-spectrum on cosmological scales",
  "title_text": "Hi intensity mapping with MeerKAT: A measurement of the 21-cm auto-spectrum on cosmological scales",
  "type": "peer-reviewed",
  "updated_at": "2026-11-06T00:21:01Z",
  "url": "https://research.draconitic.com/paper/00p5g7vh9z05g",
  "venue": "Monthly Notices of the Royal Astronomical Society",
  "versions": []
}