相关论文: Two categories of UV-upturn galaxies revealed by s…

We present models of the late stages of stellar evolution intended to explain the UV upturn phenomenon in elliptical galaxies. Such models are sensitive to values of a number of poorly-constrained physical parameters, including metallicity,…

Ultraviolet (UV) emission from galaxies is associated with hot components, whether from stellar sources or not. By making use of colour-colour diagrams, early-type galaxies (ETGs) can be classified in terms of their UV emission in mainly…

The UV upturn phenomenon observed in elliptical galaxies is attractive for its potential value as an age indicator of old stellar systems. We present our most recent population models for the UV evolution of elliptical galaxies. We confirm…

I review the observational constraints on the stars responsible for the upturn in the UV spectra of ellipticals, ranging from galaxies in the local Universe to distant clusters. In nearby galaxies, this UV upturn is produced by a minority…

We present an analysis of the far-ultraviolet upturn phenomenon (UVX) observed in elliptical galaxies and spiral galaxy bulges. Our premise is that the UV radiation from these systems emanates primarily from extreme horizontal branch (EHB)…

The ``UV upturn'' is a sharp rise in spectra of elliptical galaxies shortward of rest-frame 2500 A. It is a ubiquitous phenomenon in nearby giant elliptical galaxies, and is thought to arise primarily from low-mass evolved stars on the…

Using GALEX, UVOT and optical photometry, we explore the prevalence and strength of the UV-upturn in the spectra of quiescent early type galaxies in several nearby clusters. Even for galaxies with completely passive optical colours, there…

The far-ultraviolet is the most rapidly evolving portion of the spectrum in both very young galaxies and very old galaxies. The ``UV upturn'' in the spectra of elliptical galaxies shortward of 2000 Angstroms offers a promising probe of the…

Recent observations and modeling of globular clusters with multiple populations strongly indicate the presence of super helium-rich subpopulations in old stellar systems. Motivated by this, we have constructed new population synthesis…

The ultraviolet (UV) upturn is characterised by an unexpected up-rise of the UV flux in quiescent galaxies between the Lyman limit and 2500\AA. By making use of colour-colour diagrams, one can subdivide UV bright red-sequence galaxies in…

In the local Universe, 10% of massive elliptical galaxies are observed to exhibit a peculiar property: a substantial excess of ultraviolet emission (UVX) over what is expected from their old, red stellar populations. Several origins for the…

The so-called ultraviolet (UV) upturn of elliptical galaxies is a phenomenon characterised by the up-rise of their fluxes in bluer wavelengths, typically in the 1,200-2,500A range. This work aims at estimating the rate of occurrence of the…

The UV upturn refers to the increase in UV flux at wavelengths shorter than 3000 {\AA} observed in quiescent early-type galaxies (ETGs), which still remains a puzzle. In this study, we aim to identify ETGs showing the UV upturn phenomenon…

Whether or not metal-rich HB stars are the dominant UV source in giant elliptical galaxies (gEs) is an important question in current astronomical research. We follow up our previous evolutionary population synthesis study with quantitative…

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…

The discovery of an excess of light in the far-ultraviolet (UV) in 1969 in elliptical galaxies was a major surprise. While it is now clear that this UV excess (UV-upturn) is probably caused by an old population of helium-burning stars. Han…

The rest-frame UV contains the most sensitive indicators of age for elliptical galaxies. While the near-UV flux from young ellipticals isolates the main sequence turnoff, the far-UV flux in old ellipticals is dominated by hot horizontal…

We compare vertical profiles of the extraplanar H$\alpha$ emission to those of the UV emission for 38 nearby edge-on late-type galaxies. It is found that detection of the "diffuse" extraplanar dust (eDust), traced by the vertically…

We exploit stellar population models of absorption line indices in the ultraviolet (from 2000 - 3200 Angstrom) to study the spectra of massive galaxies. Our central aim is to investigate the occurrence at high-redshift of the UV upturn,…

Fundamental properties of the extinction curve, like the slope in the rest-frame ultraviolet (UV) and the presence/absence of a broad absorption excess centred at 2175 A (the UV bump), are investigated for a sample of 108 massive,…