scholarly journals The rise and fall of the UV upturn: z = 0.3, 0.55, and 0.7

2018 ◽  
Vol 480 (2) ◽  
pp. 2236-2246 ◽  
Author(s):  
S S Ali ◽  
M N Bremer ◽  
S Phillipps ◽  
R De Propris
Keyword(s):  
Uv Upturn

scholarly journals Evolution of the UV upturn in cluster galaxies: Abell 1689

2018 ◽  
Vol 478 (1) ◽  
pp. 541-547 ◽  
Author(s):  
S S Ali ◽  
M N Bremer ◽  
S Phillipps ◽  
R De Propris
Keyword(s):  
Cluster Galaxies ◽  
Uv Upturn

scholarly journals The GALEX Ultraviolet Virgo Cluster Survey (GUViCS)

2018 ◽  
Vol 611 ◽  
pp. A42 ◽  
Author(s):  
S. Boissier ◽  
O. Cucciati ◽  
A. Boselli ◽  
S. Mei ◽  
L. Ferrarese
Keyword(s):  
Virgo Cluster ◽  
Small Error ◽  
Early Type ◽  
Redshift Range ◽  
Cluster Galaxies ◽  
The Past ◽  
Brightest Cluster Galaxies ◽  
Binary Channel ◽  
Using Data ◽  
Uv Upturn

Context. At low redshift, early-type galaxies often exhibit a rising flux with decreasing wavelength in the 1000–2500 Å range, called “UV upturn”. The origin of this phenomenon is debated, and its evolution with redshift is poorly constrained. The observed GALEX FUV-NUV color can be used to probe the UV upturn approximately to redshift 0.5.Aim. We provide constraints on the existence of the UV upturn up to redshift ~0.4 in the brightest cluster galaxies (BCG) located behind the Virgo cluster, using data from the GUViCS survey.Methods. We estimate the GALEX far-UV (FUV) and near-UV (NUV) observed magnitudes for BCGs from the maxBCG catalog in the GUViCS fields. We increase the number of nonlocal galaxies identified as BCGs with GALEX photometry from a few tens of galaxies to 166 (64 when restricting this sample to relatively small error bars). We also estimate a central color within a 20 arcsec aperture. By using the r-band luminosity from the maxBCG catalog, we can separate blue FUV-NUV due to recent star formation and candidate upturn cases. We use Lick indices to verify their similarity to redshift 0 upturn cases.Results. We clearly detect a population of blue FUV-NUV BCGs in the redshift range 0.10–0.35, vastly improving the existing constraints at these epochs by increasing the number of galaxies studied, and by exploring a redshift range with no previous data (beyond 0.2), spanning one more Gyr in the past. These galaxies bring new constraints that can help distinguish between assumptions concerning the stellar populations causing the UV upturn phenomenon. The existence of a large number of UV upturns around redshift 0.25 favors the existence of a binary channel among the sources proposed in the literature.

scholarly journals The Age Spread Among Galaxies and the Origin of the UV Radiation from Elliptical Galaxies

1995 ◽  
Vol 164 ◽  
pp. 448-449
Author(s):  
Young-Wook Lee ◽  
Jang-Hyun Park
Keyword(s):  
Uv Radiation ◽  
Spectral Energy Distribution ◽  
Type Systems ◽  
Elliptical Galaxies ◽  
Spectral Energy ◽  
Population Synthesis ◽  
Massive Galaxies ◽  
Metal Abundance ◽  
Inside Out ◽  
Uv Upturn

Recent UV observations of elliptical galaxies are interpreted as evidence for the global second parameter phenomenon of horizontal-branch (HB) morphology within, as well as between, these galaxies. In this picture, the origin of the UV radiation is mostly due to hot HB stars and their post-HB progeny produced by the metal-poor tail of the wide metallicity distribution expected to be present in these systems. The attractive feature of this model is that the bimodal temperature distributions of HB stars (and their progeny), required to generate the 2000 Å dip of the spectral energy distribution (SED), can naturally be reproduced from the standard HB population models with large range of metal abundance (see Lee 1994, ApJ, 430, L113). Detailed population synthesis models are presented, which reproduce the systematic variation of UV upturn among elliptical galaxies (Fig 1). If age is the major second parameter, as suggested by the fossil record in our Galaxy, the observed UV color gradient and the UV upturn-total mass (mean metallicity) correlation, within and between the early-type systems, would imply, respectively, (1) that most galaxies formed from the inside out, and (2) that there is age spread among galaxies, in the sense that more massive galaxies are older (and more metal-rich in the mean) than less massive galaxies as a result of more efficient star formation (and metal enrichment) in denser environments.

The range of UV upturn strengths in early-type galaxies can be caused by dissolved metal-rich Globular Clusters

2019 ◽  
Vol 14 (S351) ◽  
pp. 112-116
Author(s):  
Paul Goudfrooij
Keyword(s):  
Globular Clusters ◽  
Dynamical Evolution ◽  
Virgo Cluster ◽  
Host Galaxy ◽  
Early Type ◽  
Luminosity Functions ◽  
Central Regions ◽  
Specific Frequency ◽  
Uv Upturn

AbstractI summarize the scenario by Goudfrooij (2018) in which the bulk of the ultraviolet (UV) upturn of giant early-type galaxies (ETGs) is due to helium-rich stellar populations that formed in massive metal-rich globular clusters (GCs) and subsequently dissolved in the strong tidal field in the central regions of the massive host galaxy. These massive GCs are assumed to show UV upturns similar to those observed recently in M87, the central galaxy in the Virgo cluster of galaxies. Data taken from the literature reveals a strong correlation between the strength of the UV upturn and the specific frequency of metal-rich GCs in ETGs. Adopting a Schechter function parametrization of GC mass functions, simulations of long-term dynamical evolution of GC systems show that this correlation can be explained by variations in the characteristic truncation mass Mc such that Mc increases with ETG luminosity in a way that is consistent with observed GC luminosity functions in ETGs. These findings suggest that the nature of the UV upturn in ETGs and the variation of its strength among ETGs are causally related to that of helium-rich populations in massive GCs, rather than intrinsic properties of field stars in ETGs.

scholarly journals White dwarfs as astrophysical probes

2008 ◽  
Vol 4 (S258) ◽  
pp. 299-306
Author(s):  
Jasonjot S. Kalirai
Keyword(s):  
White Dwarfs ◽  
Elliptical Galaxies ◽  
Main Sequence Stars ◽  
Large White ◽  
Hydrogen Burning ◽  
Nearby Star ◽  
Stellar Ages ◽  
Initial Discovery ◽  
Uv Upturn

AbstractMuch of our knowledge regarding the ages of stars derives from our understanding of the Hertzsprung-Russell Diagram. The diagram is typically dominated by hydrogen burning main-sequence stars, which historically, have been used to establish our most fundamental knowledge of stellar ages and evolution. In this brief article, I highlight how deep ground and space based imaging can uncover the stellar remnants of these hydrogen burning stars, white dwarfs. We have followed up our initial discovery of several large white dwarf populations in nearby star clusters with multiobject spectrographs. The spectroscopy allows us to characterize the properties of the remnant stars (e.g., mass, temperature, and age), which are in turn used to shed new light on fundamental astrophysical problems. Specifically, we estimate the ages of the Milky Way disk and halo, provide the inputs needed to calculate the chemical evolution of galaxies, and re-iterate the important role of HB stars in producing the UV-upturn seen in elliptical galaxies.

scholarly journals A binary model for the UV-upturn of elliptical galaxies

2007 ◽  
Vol 380 (3) ◽  
pp. 1098-1118 ◽  
Author(s):  
Z. Han ◽  
Ph. Podsiadlowski ◽  
A. E. Lynas-Gray
Keyword(s):  
Elliptical Galaxies ◽  
Binary Model ◽  
Uv Upturn

scholarly journals The UV-upturn in brightest cluster galaxies

2012 ◽  
Vol 10 (H16) ◽  
pp. 127-127
Author(s):  
S. I. Loubser ◽  
P. Sánchez-Blázquez
Keyword(s):  
Stellar Population ◽  
Control Sample ◽  
Mass Range ◽  
High Signal ◽  
Signal To Noise ◽  
Cluster Galaxies ◽  
Colour Measurements ◽  
Brightest Cluster Galaxies ◽  
Sedimentation Model ◽  
Uv Upturn

AbstractThis 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.

scholarly journals Binary Evolutionary Models

2008 ◽  
Vol 4 (S252) ◽  
pp. 349-357
Author(s):  
Z. Han ◽  
Ph. Podsiadlowski
Keyword(s):  
Globular Clusters ◽  
A Priori ◽  
Elliptical Galaxies ◽  
Ultraviolet Excess ◽  
Sdb Stars ◽  
Binary Model ◽  
Type Ia ◽  
Binary Evolution ◽  
Ehb Stars ◽  
Uv Upturn

AbstractIn this talk, we present the general principles of binary evolution and give two examples. The first example is the formation of subdwarf B stars (sdBs) and their application to the long-standing problem of ultraviolet excess (also known as UV-upturn) in elliptical galaxies. The second is for the progenitors of type Ia supernovae (SNe Ia). We discuss the main binary interactions, i.e., stable Roche lobe overflow (RLOF) and common envelope (CE) evolution, and show evolutionary channels leading to the formation of various binary-related objects. In the first example, we show that the binary model of sdB stars of Han et al. (2002, 2003) can reproduce field sdB stars and their counterparts, extreme horizontal branch (EHB) stars, in globular clusters. By applying the binary model to the study of evolutionary population synthesis, we have obtained an “a priori” model for the UV-upturn of elliptical galaxies and showed that the UV-upturn is most likely resulted from binary interactions. This has major implications for understanding the evolution of the UV excess and elliptical galaxies in general. In the second example, we introduce the single degenerate channel and the double degenerate channel for the progenitors of SNe Ia. We give the birth rates and delay time distributions for each channel and the distributions of companion stars at the moment of SN explosion for the single degenerate channel, which would help to search for the remnant companion stars observationally.

scholarly journals Color-Luminosity Relations for the Resolved Hot Stellar Populations in the Centers of M31 and M32

1999 ◽  
Vol 192 ◽  
pp. 195-202
Author(s):  
Thomas M. Brown ◽  
Henry C. Ferguson ◽  
S. A. Stanford ◽  
Jean-Michel Deharveng
Keyword(s):  
Stellar Population ◽  
Main Sequence ◽  
Uv Spectra ◽  
Agb Stars ◽  
Main Sequence Stars ◽  
Blue Stragglers ◽  
Faint Object ◽  
Luminosity Functions ◽  
Uv Upturn ◽  
Small Field Of View

We present Faint Object Camera (FOC) ultraviolet images of the central 14 x 14″ of Messier 31 and Messier 32. The hot stellar population detected in the composite UV spectra of these galaxies is partially resolved into stars, and we measure their colors and apparent magnitudes. We detect 433 stars in M31 and 138 stars in M32, down to limits of mF275W = 25.5 mag and mF175W = 24.5 mag. We investigate the luminosity functions of the sources, their spatial distribution, their color-magnitude diagrams, and their total integrated far-UV flux. Although M32 has a weaker UV upturn than M31, the luminosity functions and color-magnitude diagrams of M31 and M32 are surprisingly similar, and are inconsistent with a majority contribution from any of the following: post-AGB stars more massive than 0.56 M⊙, main sequence stars, or blue stragglers. The luminosity functions and color-magnitude diagrams are consistent with a dominant population of stars evolving from the extreme horizontal branch (EHB) along tracks of mass 0.47–0.53 M⊙. These stars are well below the detection limits of our images while on the zero-age EHB, but become detectable while in the more luminous (but shorter) post-HB phases. Our observations require that only a very small fraction of the main sequence population (2% in M31 and 0.5% in M32) in these two galaxies evolve though the EHB and post-EHB phases, with the remainder rapidly evolving through bright post-AGB evolution with few resolved stars expected in the small field of view covered by the FOC.

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