{
  "annotation_id": "557dcc45-ca6b-4b54-a2fd-aa72695c7b0e",
  "date_created": "2026-02-17T05:53:15.712000Z",
  "date_modified": "2026-02-17T05:53:15.712000Z",
  "file_hash": "34ac87cc742314e661c604e61bb474b83e1d558838c02471e9b2dc794c3ee0e5",
  "private": false,
  "record": {
    "abstract": "We present new precise measurements of electron temperatures and oxygen abundances in the southeast knot of I Zw 18, one of the most metal-poor blue compact dwarf galaxies known, using spectroscopic data from the Dark Energy Spectroscopic Instrument Data Release 1 (DESI DR1). For the first time in I Zw 18, we directly measure electron temperature in the low-ionization zone using the rarely detected [O II] $\\lambda\\lambda7320,7330$ doublet. We also detect the auroral lines [O III] $\\lambda4363$ and [S III] $\\lambda6312$, associated with high and intermediate ionization zones, respectively. We derive $T_{\\mathrm{e}}([\\mathrm{O}\\,\\mathrm{III}])=21\\,200\\pm860\\ \\mathrm{K}$, $T_{\\mathrm{e}}([\\mathrm{O}\\,\\mathrm{II}])=16\\,170\\pm950\\ \\mathrm{K}$, and $T_{\\mathrm{e}}([\\mathrm{S}\\,\\mathrm{III}])=17\\,290\\pm1750\\ \\mathrm{K}$, highlighting a significant temperature difference between ionization zones. Using these direct temperature measurements, we determine a total oxygen abundance of $12+\\log(\\mathrm{O}/\\mathrm{H})=7.066\\pm0.046$, $\\log(\\mathrm{N}/\\mathrm{O})=-1.509\\pm0.097$, and $\\log(\\mathrm{S}/\\mathrm{O})=-1.558\\pm0.041$. Our results extend the calibration of $t_2$--$t_3$ relations to the highest temperatures, providing important anchor points for the temperature structure of extremely metal-poor H II regions, including high-redshift galaxies where direct temperature measurements are especially challenging.",
    "arxiv_id": "2601.08722",
    "authors": [
      "I. A. Zinchenko",
      "J. M. V\u00edlchez",
      "C. Kehrig",
      "P. Papaderos",
      "J. E. M\u00e9ndez-Delgado"
    ],
    "categories": [
      "astro-ph.GA"
    ],
    "license": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
    "title": "First direct electron temperature measurement in [O II] zone in I Zw 18",
    "url": "https://arxiv.org/abs/2601.08722",
    "version": "v1"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "8e16e229-c661-4f17-9f63-67f067966477",
    "id": "arXiv Dataset",
    "type": "Model",
    "variant": "snapshot-2026-01-17",
    "version": "0.1.0"
  },
  "user_id": 1000002
}