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The effect of Helium-enhanced stellar populations on the ultraviolet upturn phenomenon of early-type galaxies

Published online by Cambridge University Press:  05 March 2015

Chul Chung
Affiliation:
Center for Galaxy Evolution Reasearch and Department of Astronomy, Yonsei University, Seoul 120-749, Republic of Korea email: chung@galaxy.yonsei.ac.kr
Suk-Jin Yoon
Affiliation:
Center for Galaxy Evolution Reasearch and Department of Astronomy, Yonsei University, Seoul 120-749, Republic of Korea email: chung@galaxy.yonsei.ac.kr
Young-Wook Lee
Affiliation:
Center for Galaxy Evolution Reasearch and Department of Astronomy, Yonsei University, Seoul 120-749, Republic of Korea email: chung@galaxy.yonsei.ac.kr
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Abstract

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We present new population synthesis models (Chung et al.2011) for quiescent early-type galaxies (ETGs) with UV-upturn phenomenon using relatively metal-poor and helium-enhanced subpopulations in the model. We find that the presence of helium-enhanced subpopulations in ETGs can naturally reproduce the strong UV-upturns observed in giant elliptical galaxies (Figure 1. left panel), without invoking unrealistically old ages (Park & Lee 1997). Our models with helium-enhanced subpopulations also predict that the well-known Burstein relation can be explained by the fraction of helium-enhanced subpopulation, the mean age, and the mean metallicity of the underlying stellar populations (Figure 1. right panel).

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2015 

References

Bureau, M., et al. 2011, MNRAS, 414, 1887CrossRefGoogle Scholar
Chung, C., Yoon, S.-J., & Lee, Y.-W. 2011, ApJ (Letters) 740, L45CrossRefGoogle Scholar
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