Helium rich stars produce the UV upturn. Issue Volume 15:Issue S341(2019) (November 2019)

• Record Type: Journal Article
• Authors: De Propris, R.; Ali, S.; Bremer, M. N.; Phillipps, S.
• Editors: Boquien, Médéric; Lusso, Elisabeta; Gruppioni, Carlotta; Tissera, Patricia
• Is Part Of: Proceedings of the International Astronomical Union. Volume 15:Issue S341(2019)
• Page Start: 264
• Page End: 265
• Publication Date: 2019-11
• Subjects: ultraviolet: galaxies, -- galaxies: stellar content, -- galaxies: elliptical and lenticular, -- cD, -- stars: horizontal-branch; Astronomy -- Congresses; Astronomy -- Periodicals; 520
• DOI: 10.1017/S1743921319001364
• Languages: English
• ISSNs: 1743-9213

Abstract

Abstract: 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.