THE EXTENDED He II λ4686-EMITTING REGION IN IZw 18 UNVEILED: CLUES FOR PECULIAR IONIZING SOURCES
New integral field spectroscopy has been obtained for IZw 18, the nearby lowest-metallicity galaxy considered to be our best local analog of systems forming at high redshift (z). Here we report the spatially resolved spectral map of the nebular He ii λ4686 emission in IZw 18, from which we derived f...
| Autores: | , , , , , , , |
|---|---|
| Tipo de recurso: | artículo |
| Estado: | Versión aceptada para publicación |
| Fecha de publicación: | 2015 |
| País: | España |
| Institución: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositorio: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/398039 |
| Acceso en línea: | http://hdl.handle.net/10261/398039 |
| Access Level: | acceso abierto |
| Palabra clave: | Galaxies: dwarf Galaxies: individual (IZw 18) Galaxies: ISM Galaxies: stellar content ISM: lines and bands |
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THE EXTENDED He II λ4686-EMITTING REGION IN IZw 18 UNVEILED: CLUES FOR PECULIAR IONIZING SOURCESKehrig, C.Vílchez Medina, José ManuelPérez Montero, EnriqueIglesias-Páramo, J.Brinchmann, J.Kunth, D.Durret, F.Bayo, F. M.Galaxies: dwarfGalaxies: individual (IZw 18)Galaxies: ISMGalaxies: stellar contentISM: lines and bandsNew integral field spectroscopy has been obtained for IZw 18, the nearby lowest-metallicity galaxy considered to be our best local analog of systems forming at high redshift (z). Here we report the spatially resolved spectral map of the nebular He ii λ4686 emission in IZw 18, from which we derived for the first time its total He ii-ionizing flux. Nebular He ii emission implies the existence of a hard radiation field. He ii-emitters are observed to be more frequent among high-z galaxies than for local objects. Therefore, investigating the He ii-ionizing source(s) in IZw 18 may reveal the ionization processes at high z. He ii emission in star-forming galaxies has been suggested to be mainly associated with Wolf–Rayet stars (WRs), but WRs cannot satisfactorily explain the He ii-ionization at all times, particularly at the lowest metallicities. Shocks from supernova remnants, or X-ray binaries, have been proposed as additional potential sources of He ii-ionizing photons. Our data indicate that conventional He ii-ionizing sources (WRs, shocks, X-ray binaries) are not sufficient to explain the observed nebular He iiλ4686 emission in IZw 18. We find that the He ii-ionizing radiation expected from models for either low-metallicity super-massive O stars or rotating metal-free stars could account for the He ii-ionization budget measured, while only the latter models could explain the highest values of He iiλ4686/Hβ observed. The presence of such peculiar stars in IZw 18 is suggestive and further investigation in this regard is needed. This letter highlights that some of the clues of the early universe can be found here in our cosmic backyard. © 2015. The American Astronomical Society. All rights reserved.This work has been partially funded by research projects AYA2010-21887-C04-01 from the Spanish PNAYA, and PEX2011-FQM7058 from Junta de Andalucia. F.D. and D.K. gratefully acknowledge support from the Centre National d’Etudes Spatiales. We express our appreciation to Leslie Sage for his help and suggestions. We also thank Manfred Pakull for his useful comments on this letter. Thanks are due to Jose Luis Ortiz for his careful reading of the manuscript.Peer reviewedIOP PublishingJunta de AndalucíaCentre National D'Etudes Spatiales (France)Consejo Superior de Investigaciones Científicas [https://ror.org/02gfc7t72]202520252015info:eu-repo/semantics/articlehttp://purl.org/coar/resource_type/c_6501Postprintinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/10261/398039reponame:DIGITAL.CSIC. Repositorio Institucional del CSICinstname:Consejo Superior de Investigaciones Científicas (CSIC)Inglés#PLACEHOLDER_PARENT_METADATA_VALUE#info:eu-repo/grantAgreement/MICINN//AYA2010-21887-C04-01http://dx.doi.org/10.1088/2041-8205/801/2/L28Síinfo:eu-repo/semantics/openAccessoai:digital.csic.es:10261/3980392026-05-22T06:33:51Z |
| dc.title.none.fl_str_mv |
THE EXTENDED He II λ4686-EMITTING REGION IN IZw 18 UNVEILED: CLUES FOR PECULIAR IONIZING SOURCES |
| title |
THE EXTENDED He II λ4686-EMITTING REGION IN IZw 18 UNVEILED: CLUES FOR PECULIAR IONIZING SOURCES |
| spellingShingle |
THE EXTENDED He II λ4686-EMITTING REGION IN IZw 18 UNVEILED: CLUES FOR PECULIAR IONIZING SOURCES Kehrig, C. Galaxies: dwarf Galaxies: individual (IZw 18) Galaxies: ISM Galaxies: stellar content ISM: lines and bands |
| title_short |
THE EXTENDED He II λ4686-EMITTING REGION IN IZw 18 UNVEILED: CLUES FOR PECULIAR IONIZING SOURCES |
| title_full |
THE EXTENDED He II λ4686-EMITTING REGION IN IZw 18 UNVEILED: CLUES FOR PECULIAR IONIZING SOURCES |
| title_fullStr |
THE EXTENDED He II λ4686-EMITTING REGION IN IZw 18 UNVEILED: CLUES FOR PECULIAR IONIZING SOURCES |
| title_full_unstemmed |
THE EXTENDED He II λ4686-EMITTING REGION IN IZw 18 UNVEILED: CLUES FOR PECULIAR IONIZING SOURCES |
| title_sort |
THE EXTENDED He II λ4686-EMITTING REGION IN IZw 18 UNVEILED: CLUES FOR PECULIAR IONIZING SOURCES |
| dc.creator.none.fl_str_mv |
Kehrig, C. Vílchez Medina, José Manuel Pérez Montero, Enrique Iglesias-Páramo, J. Brinchmann, J. Kunth, D. Durret, F. Bayo, F. M. |
| author |
Kehrig, C. |
| author_facet |
Kehrig, C. Vílchez Medina, José Manuel Pérez Montero, Enrique Iglesias-Páramo, J. Brinchmann, J. Kunth, D. Durret, F. Bayo, F. M. |
| author_role |
author |
| author2 |
Vílchez Medina, José Manuel Pérez Montero, Enrique Iglesias-Páramo, J. Brinchmann, J. Kunth, D. Durret, F. Bayo, F. M. |
| author2_role |
author author author author author author author |
| dc.contributor.none.fl_str_mv |
Junta de Andalucía Centre National D'Etudes Spatiales (France) Consejo Superior de Investigaciones Científicas [https://ror.org/02gfc7t72] |
| dc.subject.none.fl_str_mv |
Galaxies: dwarf Galaxies: individual (IZw 18) Galaxies: ISM Galaxies: stellar content ISM: lines and bands |
| topic |
Galaxies: dwarf Galaxies: individual (IZw 18) Galaxies: ISM Galaxies: stellar content ISM: lines and bands |
| description |
New integral field spectroscopy has been obtained for IZw 18, the nearby lowest-metallicity galaxy considered to be our best local analog of systems forming at high redshift (z). Here we report the spatially resolved spectral map of the nebular He ii λ4686 emission in IZw 18, from which we derived for the first time its total He ii-ionizing flux. Nebular He ii emission implies the existence of a hard radiation field. He ii-emitters are observed to be more frequent among high-z galaxies than for local objects. Therefore, investigating the He ii-ionizing source(s) in IZw 18 may reveal the ionization processes at high z. He ii emission in star-forming galaxies has been suggested to be mainly associated with Wolf–Rayet stars (WRs), but WRs cannot satisfactorily explain the He ii-ionization at all times, particularly at the lowest metallicities. Shocks from supernova remnants, or X-ray binaries, have been proposed as additional potential sources of He ii-ionizing photons. Our data indicate that conventional He ii-ionizing sources (WRs, shocks, X-ray binaries) are not sufficient to explain the observed nebular He iiλ4686 emission in IZw 18. We find that the He ii-ionizing radiation expected from models for either low-metallicity super-massive O stars or rotating metal-free stars could account for the He ii-ionization budget measured, while only the latter models could explain the highest values of He iiλ4686/Hβ observed. The presence of such peculiar stars in IZw 18 is suggestive and further investigation in this regard is needed. This letter highlights that some of the clues of the early universe can be found here in our cosmic backyard. © 2015. The American Astronomical Society. All rights reserved. |
| publishDate |
2015 |
| dc.date.none.fl_str_mv |
2015 2025 2025 |
| dc.type.none.fl_str_mv |
info:eu-repo/semantics/article http://purl.org/coar/resource_type/c_6501 Postprint info:eu-repo/semantics/acceptedVersion |
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article |
| status_str |
acceptedVersion |
| dc.identifier.none.fl_str_mv |
http://hdl.handle.net/10261/398039 |
| url |
http://hdl.handle.net/10261/398039 |
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Inglés |
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Inglés |
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#PLACEHOLDER_PARENT_METADATA_VALUE# info:eu-repo/grantAgreement/MICINN//AYA2010-21887-C04-01 http://dx.doi.org/10.1088/2041-8205/801/2/L28 Sí |
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info:eu-repo/semantics/openAccess |
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openAccess |
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IOP Publishing |
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IOP Publishing |
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reponame:DIGITAL.CSIC. Repositorio Institucional del CSIC instname:Consejo Superior de Investigaciones Científicas (CSIC) |
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Consejo Superior de Investigaciones Científicas (CSIC) |
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DIGITAL.CSIC. Repositorio Institucional del CSIC |
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