{
  "abstract": "Hydrogen Lyman-alpha (Ly$α$) is a prominent emission line from the circumgalactic medium (CGM). Due to its resonant nature, Ly$α$ carries imprints of the physical properties and kinematics of the cold CGM. In particular, CGM rotation can modify the Ly$α$ peak separation, which is often interpreted as a tracer of H I column density. We present 3D Monte Carlo Ly$α$ radiative-transfer simulations in a CGM-like rotating medium and examine how the emergent spectra depend on rotational velocity ($V_{\\rm rot}$), H I column density ($N_{\\rm HI}$), viewing angle, clumpiness, and intrinsic source width. We find that rotation broadens the integrated spectra and increases the peak separation, with the strongest viewing-angle dependence when rotational Doppler shifts dominate over frequency diffusion. At high $N_{\\rm HI}$, numerous scatterings reduce the sensitivity of integrated spectra to rotation, producing a degeneracy between $V_{\\rm rot}$ and $N_{\\rm HI}$. Consequently, Ly$α$ peak separation alone can overestimate $N_{\\rm HI}$ in a rotating medium. Spatially resolved halo spectra provide a clearer diagnostic: opposite sides of the rotating medium show systematic redshifted and blueshifted asymmetries associated with the line-of-sight velocity of the last-scattering gas. Such rotation-driven signatures can also contribute to velocity-map patterns often interpreted in terms of inflow or outflow, highlighting the need to consider rotation in spatially resolved Ly$α$ observations. We further show that the main signatures persist in simple clumpy media, while the halo signatures are largely insensitive to the intrinsic source width. Our results demonstrate that spatially resolved Ly$α$ observation is essential for disentangling CGM rotation from radiative-transfer effects.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.08396",
  "author_total": 4,
  "authors": [
    {
      "name": "Hee-Gyeong Kym"
    },
    {
      "name": "Seok-Jun Chang"
    },
    {
      "name": "Max Gronke"
    },
    {
      "name": "Kwang-Il Seon"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/fyzmt9ngkmmv2.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.08396",
  "fulltext_url": null,
  "id": "fyzmt9ngkmmv2",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.08396",
  "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.GA"
    ],
    [
      "openalex",
      "3103|Galaxies: Formation, Evolution, Phenomena"
    ]
  ],
  "openalex": "W7212074336",
  "pdf_url": "https://arxiv.org/pdf/2609.08396",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-08",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/fyzmt9ngkmmv2.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:19:49Z",
      "native_id": "2609.08396",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.08396"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.GA",
      "subfield": "galaxies"
    }
  ],
  "title": "The Impact of Circumgalactic Rotation on Ly$α$ Radiative Transfer",
  "title_text": "The Impact of Circumgalactic Rotation on Lyα Radiative Transfer",
  "type": "preprint",
  "updated_at": "2026-10-30T12:19:49Z",
  "url": "https://research.draconitic.com/paper/fyzmt9ngkmmv2",
  "venue": "arXiv",
  "versions": []
}