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Helium rich stars produce the UV upturn

Published online by Cambridge University Press:  10 June 2020

R. De Propris ,
S. Ali ,
M. N. Bremer  and
S. Phillipps
R. De Propris
Affiliation:
FINCA, University of Turku, 20014, Finland email: [email protected]
S. Ali
Affiliation:
H. H. Wills Physics Laboratory, University of Bristol, United Kingdom emails: [email protected], [email protected], [email protected]
M. N. Bremer
Affiliation:
H. H. Wills Physics Laboratory, University of Bristol, United Kingdom emails: [email protected], [email protected], [email protected]
S. Phillipps
Affiliation:
H. H. Wills Physics Laboratory, University of Bristol, United Kingdom emails: [email protected], [email protected], [email protected]
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Abstract

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We measure the evolution of the UV upturn color for galaxies on the red sequence in clusters at 0 < z < 0.7 and to luminosity levels L ∼ L*. We show that the UV upturn color does not change until at least z = 0.55 but becomes significantly redder at z = 0.7. This is the first detection of evolution in the UV upturn. Our observations are inconsistent with all models proposed for its origin except the presence of a population of helium enriched stars, with helium abundances above 42 % and formed at z > 4.

Keywords

ultraviolet: galaxiesgalaxies: stellar contentgalaxies: elliptical and lenticularcDstars: horizontal-branch
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 15 , Symposium S341: Challenges in Panchromatic Modelling with Next Generation Facilities , November 2019 , pp. 264 - 265
Copyright
© International Astronomical Union 2020

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