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The very massive star content of the nuclear star clusters in NGC 5253

Published online by Cambridge University Press:  28 July 2017

Linda J. Smith ,
Paul A. Crowther  and
Daniela Calzetti
Linda J. Smith
Affiliation:
European Space Agency and Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA email: lsmith@stsci.edu
Paul A. Crowther
Affiliation:
Dept. of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK email: paul.crowther@sheffield.ac.uk
Daniela Calzetti
Affiliation:
Dept. of Astronomy, University of Massachusetts – Amherst, Amherst, MA 01003, USA email: calzetti@astro.umass.edu
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Abstract

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The blue compact dwarf galaxy NGC 5253 hosts a very young starburst containing twin nuclear star clusters. Calzetti et al. (2015) find that the two clusters have an age of 1 Myr, in contradiction to the age of 3–5 Myr inferred from the presence of Wolf-Rayet (W-R) spectral features. We use Hubble Space Telescope (HST) far-ultraviolet (FUV) and ground-based optical spectra to show that the cluster stellar features arise from very massive stars (VMS), with masses greater than 100 M⊙, at an age of 1–2 Myr. We discuss the implications of this and show that the very high ionizing flux can only be explained by VMS. We further discuss our findings in the context of VMS contributing to He ii λ1640 emission in high redshift galaxies, and emphasize that population synthesis models with upper mass cut-offs greater than 100 M⊙ are crucial for future studies of young massive clusters.

Keywords

galaxies: dwarfgalaxies: individual (NGC 5253)galaxies: starburstgalaxies: star clusters: generalstars: massivestars: Wolf-Rayet
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 12 , Symposium S329: The Lives and Death-Throes of Massive Stars , November 2016 , pp. 327 - 331
Copyright
Copyright © International Astronomical Union 2017 

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