Looking for nebular He ii emission south of the multiple-massive star system, HD 5980
The nebular He ii λ1640 emission line is observed in star-forming galaxies out to large distances and can be used to constrain the properties of sources of He+-ionizing photons. For this purpose, it is crucial to understand which are the main stellar sources of these photons. In some nearby metal-po...
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| Main Authors: | , , , |
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| Other Authors: | |
| Format: | Article (Journal) |
| Language: | English |
| Published: |
March 2023
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| In: |
Monthly notices of the Royal Astronomical Society
Year: 2023, Volume: 519, Issue: 4, Pages: 5656-5672 |
| ISSN: | 1365-2966 |
| DOI: | 10.1093/mnras/stac3732 |
| Online Access: | Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1093/mnras/stac3732
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| Author Notes: | A. Sixtos, A. Wofford, A.A.C. Sander and A. Peimbert |
| Summary: | The nebular He ii λ1640 emission line is observed in star-forming galaxies out to large distances and can be used to constrain the properties of sources of He+-ionizing photons. For this purpose, it is crucial to understand which are the main stellar sources of these photons. In some nearby metal-poor starburst galaxies, nebular He ii λ4686 (optical equivalent) is accompanied by a broad underlying component, which is generally attributed to formation in the winds of classical (He-burning) Wolf-Rayet stars, primarily of the WN subtype. In such cases, the origin of the nebular component has been proposed to be the escape of He+-ionizing photons from the winds of the WN stars, at least partially. We use archival long-slit observations obtained with Focal Reducer Low Dispersion Spectrograph (FORS1) on the Very Large Telescope to look for nebular He ii λ4686 emission south of the WN6h + WN6-7 close binary in HD 5980. We only find broad He ii λ4686 emission, as far as ∼7.6 pc from the binary. A comparison with observations obtained with Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope, at a similar orbital phase, shows that the FORS1 broad He ii emission is likely contamination from the multiple-star system HD 5980. We use models to show that no significant He+-ionizing flux is expected from the WN stars in HD 5980 and that when similar stars are present in a coeval stellar population, the O stars can be far greater emitters of He+-ionizing radiation. |
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| Item Description: | Online veröffentlicht 2022 December 20 Gesehen am 27.03.2023 |
| Physical Description: | Online Resource |
| ISSN: | 1365-2966 |
| DOI: | 10.1093/mnras/stac3732 |