The ultraviolet upturn in elliptical galaxies and environmental effects

Sukyoung Yi, Jihye Lee, Yun Kyeong Sheen, Hyunjin Jeong, Hyewon Suh, Kyuseok Oh

Research output: Contribution to journalReview article

39 Citations (Scopus)

Abstract

It is suspected that the ultraviolet (UV) upturn phenomenon in elliptical galaxies and extended horizontal-branch stars in globular clusters have a common origin. An extremely high abundance of helium (Y 0.4) allows for a working hypothesis, but its origin is unclear. Peng & Nagai proposed that primordial helium sedimentation in dark halos over cosmic timescales may lead to extreme helium abundances in galaxy cluster centers. In this scenario, UV upturn should be restricted to brightest cluster galaxies (BCGs) only. This is a clear and testable prediction. We present tests of this hypothesis using galaxy clusters from Yoon et al. that were detected by both the Sloan Digital Sky Survey and the Galaxy Evolution Explorer Medium Imaging Survey. Using a new UV classification scheme based on far-UV, near-UV, and optical photometry we found that only 5% of cluster elliptical galaxies show a UV upturn, while 27% and 68% are classified as "recent star formation" and "UV-weak" ellipticals, respectively. The data reveal a modest positive dependence of the UV upturn fraction on galaxy velocity dispersion, which is in agreement with the earlier findings of Burstein et al. and possibly with the helium sedimentation theory. However, we do not see any dependency on rank or luminosity of galaxies. Besides, BCGs do not show any marked difference in UV upturn fraction or strength, which is inconsistent with the prediction. We conclude that the aforementioned helium sedimentation theory and its inferred environmental effects are not supported by the available data.

Original languageEnglish
Article number22
JournalAstrophysical Journal, Supplement Series
Volume195
Issue number2
DOIs
Publication statusPublished - 2011 Aug 1

Fingerprint

elliptical galaxies
environmental effect
helium
galaxies
sedimentation
prediction
horizontal branch stars
predictions
globular clusters
timescale
photometry
star formation
halos
luminosity

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Yi, Sukyoung ; Lee, Jihye ; Sheen, Yun Kyeong ; Jeong, Hyunjin ; Suh, Hyewon ; Oh, Kyuseok. / The ultraviolet upturn in elliptical galaxies and environmental effects. In: Astrophysical Journal, Supplement Series. 2011 ; Vol. 195, No. 2.
@article{fd7c90054080430e97b37b026d30b0e9,
title = "The ultraviolet upturn in elliptical galaxies and environmental effects",
abstract = "It is suspected that the ultraviolet (UV) upturn phenomenon in elliptical galaxies and extended horizontal-branch stars in globular clusters have a common origin. An extremely high abundance of helium (Y 0.4) allows for a working hypothesis, but its origin is unclear. Peng & Nagai proposed that primordial helium sedimentation in dark halos over cosmic timescales may lead to extreme helium abundances in galaxy cluster centers. In this scenario, UV upturn should be restricted to brightest cluster galaxies (BCGs) only. This is a clear and testable prediction. We present tests of this hypothesis using galaxy clusters from Yoon et al. that were detected by both the Sloan Digital Sky Survey and the Galaxy Evolution Explorer Medium Imaging Survey. Using a new UV classification scheme based on far-UV, near-UV, and optical photometry we found that only 5{\%} of cluster elliptical galaxies show a UV upturn, while 27{\%} and 68{\%} are classified as {"}recent star formation{"} and {"}UV-weak{"} ellipticals, respectively. The data reveal a modest positive dependence of the UV upturn fraction on galaxy velocity dispersion, which is in agreement with the earlier findings of Burstein et al. and possibly with the helium sedimentation theory. However, we do not see any dependency on rank or luminosity of galaxies. Besides, BCGs do not show any marked difference in UV upturn fraction or strength, which is inconsistent with the prediction. We conclude that the aforementioned helium sedimentation theory and its inferred environmental effects are not supported by the available data.",
author = "Sukyoung Yi and Jihye Lee and Sheen, {Yun Kyeong} and Hyunjin Jeong and Hyewon Suh and Kyuseok Oh",
year = "2011",
month = "8",
day = "1",
doi = "10.1088/0067-0049/195/2/22",
language = "English",
volume = "195",
journal = "Astrophysical Journal, Supplement Series",
issn = "0067-0049",
publisher = "IOP Publishing Ltd.",
number = "2",

}

The ultraviolet upturn in elliptical galaxies and environmental effects. / Yi, Sukyoung; Lee, Jihye; Sheen, Yun Kyeong; Jeong, Hyunjin; Suh, Hyewon; Oh, Kyuseok.

In: Astrophysical Journal, Supplement Series, Vol. 195, No. 2, 22, 01.08.2011.

Research output: Contribution to journalReview article

TY - JOUR

T1 - The ultraviolet upturn in elliptical galaxies and environmental effects

AU - Yi, Sukyoung

AU - Lee, Jihye

AU - Sheen, Yun Kyeong

AU - Jeong, Hyunjin

AU - Suh, Hyewon

AU - Oh, Kyuseok

PY - 2011/8/1

Y1 - 2011/8/1

N2 - It is suspected that the ultraviolet (UV) upturn phenomenon in elliptical galaxies and extended horizontal-branch stars in globular clusters have a common origin. An extremely high abundance of helium (Y 0.4) allows for a working hypothesis, but its origin is unclear. Peng & Nagai proposed that primordial helium sedimentation in dark halos over cosmic timescales may lead to extreme helium abundances in galaxy cluster centers. In this scenario, UV upturn should be restricted to brightest cluster galaxies (BCGs) only. This is a clear and testable prediction. We present tests of this hypothesis using galaxy clusters from Yoon et al. that were detected by both the Sloan Digital Sky Survey and the Galaxy Evolution Explorer Medium Imaging Survey. Using a new UV classification scheme based on far-UV, near-UV, and optical photometry we found that only 5% of cluster elliptical galaxies show a UV upturn, while 27% and 68% are classified as "recent star formation" and "UV-weak" ellipticals, respectively. The data reveal a modest positive dependence of the UV upturn fraction on galaxy velocity dispersion, which is in agreement with the earlier findings of Burstein et al. and possibly with the helium sedimentation theory. However, we do not see any dependency on rank or luminosity of galaxies. Besides, BCGs do not show any marked difference in UV upturn fraction or strength, which is inconsistent with the prediction. We conclude that the aforementioned helium sedimentation theory and its inferred environmental effects are not supported by the available data.

AB - It is suspected that the ultraviolet (UV) upturn phenomenon in elliptical galaxies and extended horizontal-branch stars in globular clusters have a common origin. An extremely high abundance of helium (Y 0.4) allows for a working hypothesis, but its origin is unclear. Peng & Nagai proposed that primordial helium sedimentation in dark halos over cosmic timescales may lead to extreme helium abundances in galaxy cluster centers. In this scenario, UV upturn should be restricted to brightest cluster galaxies (BCGs) only. This is a clear and testable prediction. We present tests of this hypothesis using galaxy clusters from Yoon et al. that were detected by both the Sloan Digital Sky Survey and the Galaxy Evolution Explorer Medium Imaging Survey. Using a new UV classification scheme based on far-UV, near-UV, and optical photometry we found that only 5% of cluster elliptical galaxies show a UV upturn, while 27% and 68% are classified as "recent star formation" and "UV-weak" ellipticals, respectively. The data reveal a modest positive dependence of the UV upturn fraction on galaxy velocity dispersion, which is in agreement with the earlier findings of Burstein et al. and possibly with the helium sedimentation theory. However, we do not see any dependency on rank or luminosity of galaxies. Besides, BCGs do not show any marked difference in UV upturn fraction or strength, which is inconsistent with the prediction. We conclude that the aforementioned helium sedimentation theory and its inferred environmental effects are not supported by the available data.

UR - http://www.scopus.com/inward/record.url?scp=80051776666&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=80051776666&partnerID=8YFLogxK

U2 - 10.1088/0067-0049/195/2/22

DO - 10.1088/0067-0049/195/2/22

M3 - Review article

AN - SCOPUS:80051776666

VL - 195

JO - Astrophysical Journal, Supplement Series

JF - Astrophysical Journal, Supplement Series

SN - 0067-0049

IS - 2

M1 - 22

ER -