Spatially resolved integral field spectroscopy of the ionized gas in IZW18
We present a detailed 2D study of the ionized ionized interstellar medium (ISM) of IZW18 using new Potsdam Multi-Aperture Spectrophotometer-integral field unit (PMAS-IFU) optical observations. IZW18 is a high-ionization galaxy which is among the most metal-poor starbursts in the local Universe. This...
| Authors: | , , , , , , , , |
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| Format: | article |
| Status: | Published version |
| Publication Date: | 2016 |
| Country: | España |
| Institution: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repository: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/376108 |
| Online Access: | http://hdl.handle.net/10261/376108 |
| Access Level: | Open access |
| Keyword: | H ii regions Galaxies: dwarf Galaxies: individual: IZw18 Galaxies: ISM Galaxies: starburst |
| Summary: | We present a detailed 2D study of the ionized ionized interstellar medium (ISM) of IZW18 using new Potsdam Multi-Aperture Spectrophotometer-integral field unit (PMAS-IFU) optical observations. IZW18 is a high-ionization galaxy which is among the most metal-poor starbursts in the local Universe. This makes IZW18 a local benchmark for understanding the properties most closely resembling those prevailing at distant starbursts. Our IFU aperture (~1.4 × 1.4 kpc) samples the entire IZW18 main body and an extended region of its ionized gas. Maps of relevant emission lines and emission line ratios show that higher-excitation gas is preferentially located close to the north-west knot and thereabouts. We detect a Wolf-Rayet feature near the north-west knot. We derive spatially resolved and integrated physical-chemical properties for the ionized gas in IZW18. We find no dependence between the metallicity indicator R and the ionization parameter (as traced by [O III]/[O II]) across IZW18. Over ~0.30 kpc, using the [O III] λ4363 line, we compute T[O III] values (~15 000-25 000 K), and oxygen abundances are derived from the direct determinations of T[O III]. More than 70 per cent of the higher-T[O III] (≳22 000 K) spaxels are He IIλ4686-emitting spaxels too. From a statistical analysis, we study the presence of variations in the ISM physical-chemical properties. A galaxy-wide homogeneity, across hundreds of parsecs, is seen in O/H. Based on spaxel-by-spaxel measurements, the error-weighted mean of 12 + log(O/H) = 7.11 ± 0.01 is taken as the representative O/H for IZW18. Aperture effects on the derivation of O/H are discussed. Using our IFU data we obtain, for the first time, the IZW18 integrated spectrum. © 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. |
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