The current status on the UV upturn

Yi, Sukyoung K.

doi:10.1017/s1743921310002693

Cited by 6 publications

(8 citation statements)

References 42 publications

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“…For this thesis, I made use of the MIS sample, which provides the best compromise in terms of sky coverage and image depth (see Table 2.3), a similar approach taken by previous UV upturn studies making use of GALEX data (for instance, Ree et al 2007 made use of both MIS and DIS observations to create a sample of brightest cluster galaxies, BCGs). A detailed discussion on the use of the different GALEX surveys to study the UV upturn phenomenon can be found in Yi (2008).…”

Section: Galex Gr6/plus7mentioning

confidence: 99%

The SAURON project - XVIII. The integrated UV-line-strength relations of early-type galaxies

Bureau

Jeong

et al. 2011

Monthly Notices of the Royal Astronomical Society

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Using far‐ultraviolet (FUV) and near‐ultraviolet (NUV) photometry from guest investigator programmes on the Galaxy Evolution Explorer (GALEX) satellite, optical photometry from the MDM Observatory and optical integral‐field spectroscopy from SAURON, we explore the UV–line‐strength relations of the 48 nearby early‐type galaxies in the SAURON sample. Identical apertures are used for all quantities, avoiding aperture mismatch. We show that galaxies with purely old stellar populations show well‐defined correlations of the integrated FUV −V and FUV − NUV colours with the integrated Mg b and Hβ absorption line‐strength indices, strongest for FUV − NUV. Correlations with the NUV −V colour, Fe5015 index and stellar velocity dispersion σ are much weaker. These correlations put stringent constraints on the origin of the UV‐upturn phenomenon in early‐type galaxies and highlight its dependence on age and metallicity. In particular, despite recent debate, we recover the negative correlation between FUV −V colour and Mg line strength originally publicized by Burstein et al., which we refer to as the ‘Burstein relation’, suggesting a positive dependence of the UV upturn on metallicity. We argue that the scatter in the correlations is real and present mild evidence that a strong UV excess is preferentially present in slow‐rotating galaxies. We also demonstrate that most outliers in the correlations are galaxies with current or recent star formation, some at very low levels. We believe that this sensitivity to weak star formation, afforded by the deep and varied data available for the SAURON sample, explains why our results are occasionally at odds with other recent but shallower surveys. This is supported by the analysis of a large, carefully crafted sample of more distant early‐type galaxies from the Sloan Digital Sky Survey (SDSS), more easily comparable with current and future large surveys.

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Section: Galex Gr6/plus7mentioning

confidence: 99%

The SAURON project - XVIII. The integrated UV-line-strength relations of early-type galaxies

Bureau

Jeong

et al. 2011

Monthly Notices of the Royal Astronomical Society

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“…The Ultraviolet Upturn or Excess is an unexpected rise in flux in the spectral energy distributions of early-type galaxies shortwards of 2500Å. It appears to be a nearly ubiquitous property of spheroids and bulge-dominated galaxies (see, e.g., Yi 2008Yi , 2010 for a recent review) although their generally old, metal-rich and quiescent stellar populations (e.g., Thomas et al 2005Thomas et al , 2010 should contain no sources capable of providing significant flux below the 4000Å break. While many candidates have been proposed, the source population is generally agreed to consist of hot horizontal branch (HB) stars (Greggio & Renzini 1990;Brown et al 1998a) and it now appears most likely that this population is heliumrich and formed in situ at high redshift (Ali et al 2018a,b,c).…”

Section: Introductionmentioning

confidence: 99%

Environmental effects on the UV upturn in local clusters of galaxies

Ali

Bremer

Phillipps

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We explore the dependence of UV upturn colours in early type cluster galaxies on the properties of their parent clusters (such as velocity dispersion and X-ray luminosity) and on the positions and kinematics of galaxies within them. We use a sample of 24 nearby clusters with highly complete spectroscopy and optical/infrared data to select a suitable sample of red sequence galaxies, whose FUV and NUV magnitudes we measure from archival GALEX data. Our results show that the UV upturn colour has no dependence on cluster properties and has the same range in all clusters. There is also no dependence on the projected position within clusters or on line-of-sight velocity. Therefore, our conclusion is that the UV upturn phenomenon is an intrinsic feature of cluster early type galaxies, irrespective of their cluster environment.

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“…In spiral and irregular galaxies, flux emitted in the UV acts as an excellent measure of the current star formation rate (Gil de Paz et al 2007). In the case of (mostly quiescent) early-type galaxies, the flux at wavelengths shorter than 1800Å (FUV) is believed to be produced by hot, low mass Horizontal Branch (HB) stars, although the mechanism with which an old population can develop hot stars is still hotly debated (see Yi 2008). For the non-quiescent, low redshift elliptical galaxies, analysis of UV wavelengths longer than 1800Å (NUV) is a useful indicator of residual star formation (Pipino et al 2009).…”

Section: Introductionmentioning

confidence: 99%

“…This hypothesis is motivated by globular cluster observations containing peculiar features in the colour magnitude diagram that can only be explained by the presence of super-helium-rich subpopulations (D' Antona & Caloi 2004;Norris 2004;D'Antona et al 2005; Lee et al 2005;Piotto et al 2005). These populations could be a major source of FUV flux in quiescent el-liptical galaxies, although studies suggest that the deduced value of the helium abundance is too small to be influential on galactic scales (Lee et al 2005;Yi 2008). However, in the centres of clusters, an extra source of helium could come from sedimentation processes (Peng & Nagai 2009).…”

Section: Introductionmentioning

confidence: 99%

The UV-upturn in brightest cluster galaxies

Loubser¹,

Sánchez‐Blázquez²

2012

Proc. IAU

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This study is part of a series devoted to the investigation of a large sample of brightest cluster galaxies (BCGs), their properties and the relationships between these and the properties of the host clusters. In this paper, we compare the stellar population properties derived from high signal-to-noise, optical long-slit spectra with the GALEX ultraviolet (UV) colour measurements for 36 nearby BCGs to understand the diversity in the most rapidly evolving feature in old stellar systems, the UV-upturn. We investigate: (1) the possible differences between the UV-upturn of BCGs and those of a control sample of ordinary ellipticals in the same mass range, as well as possible correlations between the UV-upturn and other general properties of the galaxies;(2) possible correlations between the UV-upturn and the properties of the host clusters; (3) recently proposed scenarios where helium-sedimentation in the cluster centre can produce an enhanced UV-upturn. We find systematic differences between the UV-colours of BCGs and ordinary ellipticals, but we do not find correlations between these colours and the properties of the host clusters. Furthermore, the observations do not support the predictions made by the helium-sedimentation model as an enhancer of the UV-upturn.

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The current status on the UV upturn

Cited by 6 publications

References 42 publications

The SAURON project - XVIII. The integrated UV-line-strength relations of early-type galaxies

The SAURON project - XVIII. The integrated UV-line-strength relations of early-type galaxies

Environmental effects on the UV upturn in local clusters of galaxies

The UV-upturn in brightest cluster galaxies

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