{
  "abstract": "Balmer absorption is common among little red dots (LRDs), but absorbers at or redward of systemic are rare, occurring in only $\\sim10-15$\\% of H$α$ absorbers. In this paper, we study two such exceptional cases with deep JWST/NIRSpec spectroscopy: 15 hr of high-resolution (G395H) observations of RUBIES-EGS-49140 (z=6.68), resolving the absorption in all four transitions from H$α$ through H$δ$, and medium-resolution spectroscopy (10 hr of G235M, 2 hr of G395M) of UNCOVER-A2744-45924 (z=4.46; 1.7x magnification). Both sources are among the optically reddest and most luminous LRDs known, and both show deep, near-systemic Balmer absorption troughs. We find two systematic trends along the Balmer series: the absorption centroids become more redshifted toward higher-order transitions, while the absorbed equivalent widths decline only weakly with increasing order, far less than expected from the atomic optical-depth ratios for a single attenuating screen. Ca\\,{\\sc{ii}}\\,K is detected in absorption in both sources, whose offset follows the H$α$ trough rather than the more redshifted higher-order Balmer lines. We further report the detection of a broad base in [Ne\\,{\\sc{iii}}]\\,$λ$3870, along with broad [O\\,{\\sc{iii}}]\\,$λ$4364, [O\\,{\\sc{iii}}]\\,$\\lambda5008$, and He\\,{\\sc{i}}\\,$\\lambda5877,\\lambda7067$, while He\\,{\\sc{ii}}\\,$λ$4687 remains undetected or weak. Standard AGN photoionization models cannot reproduce the observed line ratios, whereas AGNs with high gas densities provide a consistent explanation, as also indicated by the anomalously high He\\,{\\sc{i}}\\,$\\lambda7067/\\lambda5877$ ratio. A possible explanation for the relative strengths of the Balmer absorption lines could be a dense, optically thick medium whose re-emission modifies their apparent absorption strengths, while the velocity progression may arise from stratification in the absorbing gas.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.22623",
  "author_total": 24,
  "authors": [
    {
      "name": "Bingjie Wang"
    },
    {
      "name": "Jenny E. Greene"
    },
    {
      "name": "Hanpu Liu"
    },
    {
      "name": "Nicholas Kaaz"
    },
    {
      "name": "Gabriel B. Brammer"
    },
    {
      "name": "Raphael E. Hviding"
    },
    {
      "name": "Ivo Labbé"
    },
    {
      "name": "Joel Leja"
    },
    {
      "name": "Jorryt Matthee"
    },
    {
      "name": "Rohan P. Naidu"
    },
    {
      "name": "Alberto Torralba"
    },
    {
      "name": "Josephine F. W. Baggen"
    },
    {
      "name": "Nikko J. Cleri"
    },
    {
      "name": "Seiji Fujimoto"
    },
    {
      "name": "Lukas J. Furtak"
    },
    {
      "name": "Anna de Graaff"
    },
    {
      "name": "Michaela Hirschmann"
    },
    {
      "name": "Vasily Kokorev"
    },
    {
      "name": "Erini Lambrides"
    },
    {
      "name": "Ian McConachie"
    },
    {
      "name": "Erica J. Nelson"
    },
    {
      "name": "Adèle Plat"
    },
    {
      "name": "Weichen Wang"
    },
    {
      "name": "Adi Zitrin"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/7kkf7530rr66d.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.22623",
  "fulltext_url": null,
  "id": "7kkf7530rr66d",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.22623",
  "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.GA"
    ],
    [
      "openalex",
      "3103|Galaxies: Formation, Evolution, Phenomena"
    ]
  ],
  "openalex": "W7214018311",
  "pdf_url": "https://arxiv.org/pdf/2609.22623",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-18",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/7kkf7530rr66d.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:23:19Z",
      "native_id": "2609.22623",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.22623"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.GA",
      "subfield": "galaxies"
    }
  ],
  "title": "Balmer Absorption Series and Broad Metal Lines in Two Luminous Little Red Dots",
  "title_text": "Balmer Absorption Series and Broad Metal Lines in Two Luminous Little Red Dots",
  "type": "preprint",
  "updated_at": "2026-10-30T12:23:19Z",
  "url": "https://research.draconitic.com/paper/7kkf7530rr66d",
  "venue": "arXiv",
  "versions": []
}