First direct electron temperature measurement in [O II] zone in I Zw 18
We present new precise measurements of the electron temperatures and oxygen abundances in the southeast knot of I Zw 18, one of the most metal poor blue compact dwarf galaxies known. We used spectroscopic data from the Dark Energy Spectroscopic Instrument Data Release 1 (DESI DR1). For the first tim...
| Autores: | , , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2026 |
| País: | España |
| Institución: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositorio: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:dnet:digitalcsic_::decb213316dc3d0c2f1a826aac2ba739 |
| Acceso en línea: | http://hdl.handle.net/10261/428599 |
| Access Level: | acceso abierto |
| Palabra clave: | ISM: abundances HII regions Galaxies: abundances Galaxies: dwarf Galaxies: ISM |
| Sumario: | We present new precise measurements of the electron temperatures and oxygen abundances in the southeast knot of I Zw 18, one of the most metal poor blue compact dwarf galaxies known. We used spectroscopic data from the Dark Energy Spectroscopic Instrument Data Release 1 (DESI DR1). For the first time in I Zw 18, we directly measured the electron temperature in the low-ionization zone using the rarely detected [O II]λλ7320,7330 doublet. We also detected the [O III]λ4363 and [S III]λ6312 auroral lines, which are associated with high- and intermediate-ionization zones, respectively. We derived Te ([O III]) = 21 200 ± 860 K, Te ([O II]) = 16 170 ± 950 K, and Te ([S III]) = 17 290±1750, which highlights a significant temperature difference between the ionization zones. Using these direct temperature measurements, we determined a total oxygen abundance of 12+log(O/H) = 7.066 ± 0.046, log(N/O) = –1.509 ± 0.097, and log(S/O) = –1.558 ± 0.041. Our results extend the calibration of t 2 − t 3 relations to the highest temperatures and provide important anchor points for the temperature structure of extremely metal-poor H II regions, including high-redshift galaxies, for which direct temperature measurements are especially challenging. © The Authors 2026. |
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