{
  "abstract": "Based on LAMOST Medium-Resolution Spectroscopic Survey of Nebulae (MRS-N) data and WISE Galactic HII region catalog, we construct a sample of 280 Galactic HII regions and candidates in the Outer Galaxy (80$^{\\circ}$ $\\lesssim$ l $\\lesssim$ 220$^{\\circ}$). Using MRS-N optical spectra, we measure four emission lines (H$α$, [NII]$λ$6584, [SII]$λλ$6717,6731) and use line-ratios to spectroscopically confirm 255 HII regions, including 90 previously \"Known\" HII regions and 165 newly classified ones. We measure their $T_{\\rm e}$, $n_{\\rm e}$ and oxygen abundance, and determine distances via associated OB stars and the kinematic method. The sample spans $R_{\\rm gal}$ from 8.16 to 15.36 kpc, enabling investigation of radial gradients in physical properties. We find [NII]/H$α$ and [SII]/H$α$ decrease with increasing $R_{\\rm gal}$, while [SII]/[NII] remains nearly flat; these trends are quite different from diffuse ionized gas (DIG). We derive the $T_{\\rm e}$ gradient of 344.530 $\\pm$ 78.083 K kpc$^{-1}$, and the $\\log n_{\\rm e}$ gradient of -0.143 $\\pm$ 0.041 cm$^{-3}$ kpc$^{-1}$. Oxygen abundance shows a steep slope of -0.044 $\\pm$ 0.010 dex kpc$^{-1}$ in the inner disk and a shallow slope of -0.016 $\\pm$ 0.005 dex kpc$^{-1}$ in the outer disk, with a global slope of -0.014 $\\pm$ 0.005 dex kpc$^{-1}$. We also examine the two-dimensional distributions of $T_{\\rm e}$, $n_{\\rm e}$, and oxygen abundance, and find the gradients vary with azimuth. There is no obvious difference between spiral arm and interarm regions, and no trend appears along individual arms. From [NII]/H$α$-[SII]$λ$6717/H$α$ diagram, HII regions have a S$^+$/S ratio (0.32), lower than DIG (0.43); however, heavy overlap prevents clear separation from this diagram alone.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": "Journal reference: AJ, 2026, 172, 168",
  "arxiv": "2607.27662",
  "author_total": 13,
  "authors": [
    {
      "name": "Yunning Zhao"
    },
    {
      "name": "Wei Zhang"
    },
    {
      "name": "Lin Ma"
    },
    {
      "name": "Shiming Wen"
    },
    {
      "name": "Tao Jing"
    },
    {
      "name": "Cheng Li"
    },
    {
      "name": "Zheng Zheng"
    },
    {
      "name": "Aiyuan Yang"
    },
    {
      "name": "Shichao Han"
    },
    {
      "name": "Juanjuan Ren"
    },
    {
      "name": "Jianjun Chen"
    },
    {
      "name": "Hong Wu"
    },
    {
      "name": "Yongheng Zhao"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/6tnnxhep2csh1.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2607.27662",
  "fulltext_url": null,
  "id": "6tnnxhep2csh1",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2607.27662",
  "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": null,
  "pdf_url": "https://arxiv.org/pdf/2607.27662",
  "pmcid": null,
  "pmid": null,
  "published": "2026-07-30",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/6tnnxhep2csh1.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:17:22Z",
      "native_id": "2607.27662",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2607.27662"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.GA",
      "subfield": "galaxies"
    }
  ],
  "title": "Galactic HII regions in LAMOST Medium-Resolution Spectroscopic Survey of Nebulae",
  "title_text": "Galactic HII regions in LAMOST Medium-Resolution Spectroscopic Survey of Nebulae",
  "type": "preprint",
  "updated_at": "2026-10-30T12:17:22Z",
  "url": "https://research.draconitic.com/paper/6tnnxhep2csh1",
  "venue": "arXiv",
  "versions": [
    {
      "doi": "10.3847/1538-3881/ae930f",
      "pid": null,
      "relation": "published-as",
      "title": null,
      "venue": null
    }
  ]
}