Helium rich stars produce the UV upturn

R. De Propris; S. Ali; M. N. Bremer; S. Phillipps

doi:10.1017/s1743921319001364

Helium rich stars produce the UV upturn

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319001364 ◽

2019 ◽

Vol 15 (S341) ◽

pp. 264-265

Author(s):

R. De Propris ◽

S. Ali ◽

M. N. Bremer ◽

S. Phillipps

Keyword(s):

Uv Upturn ◽

Red Sequence

AbstractWe measure the evolution of the UV upturn color for galaxies on the red sequence in clusters at 0 < z < 0.7 and to luminosity levels L ∼ L*. We show that the UV upturn color does not change until at least z = 0.55 but becomes significantly redder at z = 0.7. This is the first detection of evolution in the UV upturn. Our observations are inconsistent with all models proposed for its origin except the presence of a population of helium enriched stars, with helium abundances above 42 % and formed at z > 4.

Download Full-text

UV bright red-sequence galaxies: a comparative study between UV upturn and UV weak systems Maria

10.11606/t.14.2020.tde-14122020-155924 ◽

2020 ◽

Author(s):

Maria Luiza Linhares Dantas

Keyword(s):

Comparative Study ◽

Uv Upturn ◽

Red Sequence

Download Full-text

UV color-color relation of early-type galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314004918 ◽

2012 ◽

Vol 10 (H16) ◽

pp. 130-130

Author(s):

Chang H. Ree ◽

Hyunjin Jeong ◽

Kyuseok Oh ◽

Chul Chung ◽

Joon Hyeop Lee ◽

...

Keyword(s):

Spectral Shape ◽

Minority Population ◽

Horizontal Branch ◽

Early Type ◽

Spectral Slope ◽

Canonical Models ◽

Data Support ◽

Uv Excess ◽

Uv Upturn ◽

Red Sequence

AbstractThe ultraviolet (UV) color-color relation of early-type galaxies (ETGs) in the nearby universe (0.05 < z < 0.12) is re-examined with the latest GALEX GR6 and SDSS DR7 data. By drawing the FUV – NUV (as a measure of UV temperature) versus FUV – r (as a measure of UV amplitude) color-color diagram for the morphologically-cleaned, spectroscopically-cleaned sample of ~3700 quiescent ETGs, we find that the “old and dead“ ETGs consist of a well-defined sequence in UV colors, the “UV red sequence”, so that the stronger UV excess galaxies should have a harder UV spectral shape systematically. However, the observed UV spectral slope is too steep to be reproduced by the canonical models in which the UV flux is mainly controlled by age or metallicity parameters. The observed data support the helium enhancement scenario in which the UV spectral shape of UV upturn (FUV – NUV < 0.9; FUV – r ~ 6) galaxies may be governed by the minority population of helium-enhanced horizontal-branch (HB) stars.

Download Full-text

Galaxy And Mass Assembly (GAMA): Defining passive galaxy samples and searching for the UV upturn

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz3552 ◽

2019 ◽

Vol 492 (2) ◽

pp. 2128-2139

Author(s):

S Phillipps ◽

S S Ali ◽

M N Bremer ◽

R De Propris ◽

A E Sansom ◽

...

Keyword(s):

Star Formation ◽

Cluster Galaxies ◽

Star Forming ◽

Stellar Component ◽

Wide Range ◽

Other Information ◽

Mass Assembly ◽

Clean Sample ◽

Uv Upturn ◽

Red Sequence

ABSTRACT We use data from the GAMA and GALEX surveys to demonstrate that the UV upturn, an unexpected excess of ultraviolet flux from a hot stellar component, seen in the spectra of many early-type galaxies, arises from processes internal to individual galaxies with no measurable influence from the galaxies’ larger environment. We first define a clean sample of passive galaxies without a significant contribution to their UV flux from low-level star formation. We confirm that galaxies with the optical colours of red sequence galaxies often have signs of residual star formation, which, without other information, would prevent a convincing demonstration of the presence of UV upturns. However, by including (NUV−u) and WISE (W2–W3) colours, and FUV data where it exists, we can convincingly constrain samples to be composed of non-star-forming objects. Using such a sample, we examine GALEX photometry of low-redshift GAMA galaxies in a range of low-density environments, from groups to the general field, searching for UV upturns. We find a wide range of (NUV−r) colours, entirely consistent with the range seen – and attributed to the UV upturn – in low-redshift red sequence cluster galaxies. The range of colours is independent of group multiplicity or velocity dispersion, with isolated passive galaxies just as likely to have blue UV-to-optical colours, implying significant upturn components, as those in richer groups and in the previous data on clusters. This is supported by equivalent results for (FUV−r) colours which are clear indicators of upturn components.

Download Full-text

UV bright red-sequence galaxies: how do UV upturn systems evolve in redshift and stellar mass?

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz3609 ◽

2019 ◽

Vol 492 (2) ◽

pp. 2996-3011 ◽

Cited By ~ 2

Author(s):

M L L Dantas ◽

P R T Coelho ◽

R S de Souza ◽

T S Gonçalves

Keyword(s):

Emission Line ◽

Galaxy Evolution ◽

Stellar Mass ◽

Sloan Digital Sky Survey ◽

Uv Emission ◽

Mass Assembly ◽

Matched Data ◽

Line Classification ◽

Uv Upturn ◽

Red Sequence

ABSTRACT The so-called ultraviolet (UV) upturn of elliptical galaxies is a phenomenon characterized by the up-rise of their fluxes in bluer wavelengths, typically in the 1200–2500 Å range. This work aims at estimating the rate of occurrence of the UV upturn over the entire red-sequence population of galaxies that show significant UV emission. This assessment is made considering it as function of three parameters: redshift, stellar mass, and – what may seem counter-intuitive at first – emission-line classification. We built a multiwavelength spectrophotometric catalogue from the Galaxy Mass Assembly survey, together with aperture-matched data from Galaxy Evolution Explorer Medium-Depth Imaging Survey (MIS) and Sloan Digital Sky Survey, covering the redshift range between 0.06 and 0.40. From this sample, we analyse the UV emission among UV bright galaxies, by selecting those that occupy the red-sequence locus in the (NUV− r) × (FUV−NUV) chart; then, we stratify the sample by their emission-line classes. To that end, we make use of emission-line diagnostic diagrams, focusing the analysis in retired/passive lineless galaxies. Then, a Bayesian logistic model was built to simultaneously deal with the effects of all galaxy properties (including emission-line classification or lack thereof). The main results show that retired/passive systems host an up-rise in the fraction of UV upturn for redshifts between 0.06 and 0.25, followed by an in-fall up to 0.35. Additionally, we show that the fraction of UV upturn hosts rises with increasing stellar mass.

Download Full-text

The growth of the red-sequence in clusters since ≃1

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310008410 ◽

2009 ◽

Vol 5 (H15) ◽

pp. 88-88

Author(s):

Roberto P. Muñoz ◽

L. F. Barrientos ◽

B. P. Koester ◽

D. G. Gilbank ◽

M. D. Gladders ◽

...

Keyword(s):

Star Formation ◽

Galaxy Clusters ◽

Evolutionary Model ◽

Large Ensemble ◽

Cluster Galaxies ◽

Nir Imaging ◽

Measured Change ◽

First Time ◽

The Universe ◽

Red Sequence

AbstractWe use deep nIR imaging of 15 galaxy clusters at z ≃ 1 to study the build-up of the red-sequence in rich clusters since the Universe was half its present age. We measured, for the first time, the luminous-to-faint ratio of red-sequence galaxies at z=1 from a large ensemble of clusters, and found an increase of 100% in the ratio of luminous-to-faint red-sequence galaxies from z=0.45 to 1.0. The measured change in this ratio as function of redshift is well-reproduced by a simple evolutionary model developed in this work, that consists in an early truncation of the star formation for bright cluster galaxies and a delayed truncation for faint cluster galaxies.

Download Full-text