New Insight on the Origin of the Double Red Clump in the Milky Way Bulge

Seok Joo Joo, Young Wook Lee, Chul Chung

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

The double red clump (RC) observed in the Milky Way bulge is widely interpreted as evidence for an X-shaped structure. We have recently suggested, however, an alternative interpretation based on the multiple population phenomenon, where the bright RC is from helium-enhanced second-generation stars (G2), while the faint RC is representing first-generation stars (G1) with normal helium abundance. Here, our RC models are constructed in a large parameter space to see the effects of metallicity, age, and helium abundance on the double RC feature. Our models show that the luminosity of RC stars is mainly affected by helium abundance, while the RC color is primarily affected by metallicity. The effect of age is relatively small, unless it is older than 12 Gyr or much younger than 6 Gyr. The observed double RC feature can therefore be reproduced in a relatively large parameter space, once ΔY between G2 and G1 is assumed to be greater than ∼0.10. We further show that the longitude dependence of the double RC feature at , which was pointed out by Gonzalez et al. as a potential problem of our model, is well explained in our scenario by a classical bulge embedded in a tilted bar.

Original languageEnglish
Article number98
JournalAstrophysical Journal
Volume840
Issue number2
DOIs
Publication statusPublished - 2017 May 10

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clumps
helium
stars
metallicity
longitude
luminosity
color
effect
parameter

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

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title = "New Insight on the Origin of the Double Red Clump in the Milky Way Bulge",
abstract = "The double red clump (RC) observed in the Milky Way bulge is widely interpreted as evidence for an X-shaped structure. We have recently suggested, however, an alternative interpretation based on the multiple population phenomenon, where the bright RC is from helium-enhanced second-generation stars (G2), while the faint RC is representing first-generation stars (G1) with normal helium abundance. Here, our RC models are constructed in a large parameter space to see the effects of metallicity, age, and helium abundance on the double RC feature. Our models show that the luminosity of RC stars is mainly affected by helium abundance, while the RC color is primarily affected by metallicity. The effect of age is relatively small, unless it is older than 12 Gyr or much younger than 6 Gyr. The observed double RC feature can therefore be reproduced in a relatively large parameter space, once ΔY between G2 and G1 is assumed to be greater than ∼0.10. We further show that the longitude dependence of the double RC feature at , which was pointed out by Gonzalez et al. as a potential problem of our model, is well explained in our scenario by a classical bulge embedded in a tilted bar.",
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New Insight on the Origin of the Double Red Clump in the Milky Way Bulge. / Joo, Seok Joo; Lee, Young Wook; Chung, Chul.

In: Astrophysical Journal, Vol. 840, No. 2, 98, 10.05.2017.

Research output: Contribution to journalArticle

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