Crowther, P.A. (2008) Wolf-Rayet Populations at High Metallicity. In: Israelian, G. and Meynet, G., (eds.) The Metal-Rich Universe. Cambridge Contemporary Astrophysics . Cambridge University Press , pp. 276-287. ISBN 9780521879989
Abstract
Observed properties of Wolf-Rayet stars at high metallicity are reviewed. Wolf-Rayet stars are more common at higher metallicity, as a result of stronger mass-loss during earlier evolutionary phases with late WC subtypes signatures of solar metallicity or higher. Similar numbers of early (WC4-7) and late (WC8-9) stars are observed in the Solar neighbourhood, whilst late subtypes dominate at higher metallicities, such as Westerlund 1 in the inner Milky Way and in M83. The observed trend to later WC subtype within metal-rich environments is intimately linked to a metallicity dependence of WR stars, in the sense that strong winds preferentially favour late subtypes. This has relevance to (a) the upper mass limit in metal-rich galaxies such as NGC 3049, due to softer ionizing fluxes from WR stars at high metallicity; (b) evolutionary models including a WR metallicity dependence provide a better match to the observed N(WC)/N(WN) ratio. The latter conclusion partially rests upon the assumption of constant line luminosities for WR stars, yet observations and theoretical atmospheric models reveal higher line fluxes at high metallicity.
Metadata
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Copyright, Publisher and Additional Information: | © Cambridge University Press 2008. This is an author produced version of a chapter subsequently published in The Metal-Rich Universe edited by Israelian, G and Meynet, G. This version is free to view and download for personal use only. Not for re-distribution, re-sale or use in derivative works. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | astro-ph; astro-ph |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > Department of Physics and Astronomy (Sheffield) |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 25 Aug 2016 13:23 |
Last Modified: | 28 Mar 2018 20:50 |
Published Version: | http://www.cambridge.org/us/academic/subjects/astr... |
Status: | Published |
Publisher: | Cambridge University Press |
Series Name: | Cambridge Contemporary Astrophysics |
Refereed: | Yes |
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