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 Stellar populations in brightest cluster galaxies

2009 ◽  
Vol 5 (S262) ◽  
pp. 374-375
Author(s):  
S. I. Loubser ◽  
P. Sánchez-Blázquez ◽  
I. K. Soechting ◽  
A. E. Sansom
Keyword(s):  
Stellar Population ◽  
Mass Range ◽  
Elliptical Galaxies ◽  
High Signal ◽  
Cluster Galaxies ◽  
Cooling Flows ◽  
Internal Parameters ◽  
Brightest Cluster Galaxies ◽  
Derived Properties ◽  
Internal Properties

AbstractWe present the results of an investigation of a large sample of brightest cluster galaxies (BCGs), their kinematic and stellar population properties and the relationships between these and the properties of the host clusters. We have obtained high signal-to-noise, long-slit spectra of 49 BCGs in the nearby Universe with the Gemini and WHT telescopes. From this, we have measured the radial velocity and velocity dispersion profiles, and used the Lick system of absorption indices to derive Single Stellar Population (SSP)-equivalent ages, metallicities and α-abundance ratios. The results were systematically compared with those of large samples of ordinary elliptical galaxies in the same mass range. In addition, the derived properties were tested for possible correlations with the internal properties of the galaxies (mass, rotation and luminosity) and the properties of the host clusters (density, mass, distance to X-ray peak and cooling flows). We address the following questions: how the kinematic and stellar population properties differ from those of ordinary giant elliptical galaxies; and whether these properties are more influenced by the internal parameters of the BCGs or the properties of the clusters.

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 Dynamical masses of brightest cluster galaxies – II. Constraints on the stellar IMF

2020 ◽  
Vol 500 (3) ◽  
pp. 4153-4165
Author(s):  
S I Loubser ◽  
H Hoekstra ◽  
A Babul ◽  
Y M Bahé ◽  
M Donahue
Keyword(s):  
Gravitational Lensing ◽  
Stellar Population ◽  
Population Analysis ◽  
Stellar Populations ◽  
Stellar Mass ◽  
Initial Mass Function ◽  
Dynamical Mass ◽  
Cluster Galaxies ◽  
Brightest Cluster Galaxies ◽  
Mass Profiles

ABSTRACT We use stellar and dynamical mass profiles, combined with a stellar population analysis, of 32 brightest cluster galaxies (BCGs) at redshifts of 0.05 ≤$z$ ≤ 0.30, to place constraints on their stellar initial mass function (IMF). We measure the spatially resolved stellar population properties of the BCGs, and use it to derive their stellar mass-to-light ratios ($\Upsilon _{\star \rm POP}$). We find young stellar populations (<200 Myr) in the centres of 22 per cent of the sample, and constant $\Upsilon _{\star \rm POP}$ within 15 kpc for 60 per cent of the sample. We further use the stellar mass-to-light ratio from the dynamical mass profiles of the BCGs ($\Upsilon _{\star \rm DYN}$), modelled using a multi-Gaussian expansion and Jeans Anisotropic Method, with the dark matter contribution explicitly constrained from weak gravitational lensing measurements. We directly compare the stellar mass-to-light ratios derived from the two independent methods, $\Upsilon _{\star \rm POP}$ (assuming some IMF) to $\Upsilon _{\star \rm DYN}$ for the subsample of BCGs with no young stellar populations and constant $\Upsilon _{\star \rm POP}$. We find that for the majority of these BCGs, a Salpeter (or even more bottom-heavy) IMF is needed to reconcile the stellar population and dynamical modelling results although for a small number of BCGs, a Kroupa (or even lighter) IMF is preferred. For those BCGs better fit with a Salpeter IMF, we find that the mass-excess factor against velocity dispersion falls on an extrapolation (towards higher masses) of known literature correlations. We conclude that there is substantial scatter in the IMF amongst the highest mass galaxies.

scholarly journals Clocking the formation of today’s largest galaxies: wide field integral spectroscopy of brightest cluster galaxies and their surroundings

2019 ◽  
Vol 491 (2) ◽  
pp. 2617-2638 ◽  
Author(s):  
Louise O V Edwards ◽  
Matthew Salinas ◽  
Steffanie Stanley ◽  
Priscilla E Holguin West ◽  
Isabella Trierweiler ◽  
...  
Keyword(s):  
Velocity Dispersion ◽  
Minor Component ◽  
High Signal ◽  
Wide Field ◽  
Cluster Galaxies ◽  
Brightest Cluster Galaxies ◽  
The Galaxy ◽  
Formation And Evolution ◽  
Intracluster Light ◽  
A Minor

ABSTRACT The formation and evolution of local brightest cluster galaxies (BCGs) is investigated by determining the stellar populations and dynamics from the galaxy core, through the outskirts and into the intracluster light (ICL). Integral spectroscopy of 23 BCGs observed out to $4\, r_{e}$ is collected and high signal-to-noise regions are identified. Stellar population synthesis codes are used to determine the age, metallicity, velocity, and velocity dispersion of stars within each region. The ICL spectra are best modelled with populations that are younger and less metal-rich than those of the BCG cores. The average BCG core age of the sample is $\rm 13.3\pm 2.8\, Gyr$ and the average metallicity is $\rm [Fe/H] = 0.30\pm 0.09$, whereas for the ICL the average age is $\rm 9.2\pm 3.5\, Gyr$ and the average metallicity is $\rm [Fe/H] = 0.18\pm 0.16$. The velocity dispersion profile is seen to be rising or flat in most of the sample (17/23), and those with rising values reach the value of the host cluster’s velocity dispersion in several cases. The most extended BCGs are closest to the peak of the cluster’s X-ray luminosity. The results are consistent with the idea that the BCG cores and inner regions formed quickly and long ago, with the outer regions and ICL forming more recently, and continuing to assemble through minor merging. Any recent star formation in the BCGs is a minor component, and is associated with the cluster cool core status.

scholarly journals Stellar population gradients in brightest cluster galaxies

2012 ◽  
Vol 8 (S295) ◽  
pp. 316-316
Author(s):  
S. I. Loubser ◽  
P. Sánchez-Blázquez
Keyword(s):  
Stellar Population ◽  
Velocity Dispersion ◽  
Elliptical Galaxies ◽  
Negative Slope ◽  
High Quality ◽  
X Ray ◽  
Cluster Galaxies ◽  
Central Galaxy ◽  
Brightest Cluster Galaxies

AbstractWe present the stellar population and velocity dispersion gradients for a sample of 24 brightest cluster galaxies (BCGs) in the nearby Universe for which we have obtained high quality long-slit spectra at the Gemini telescopes. With the aim of studying the possible connection between the formation of the BCGs and their host clusters, we explore the relations between the stellar population gradients and properties of the host clusters, as well as the possible connections between the stellar population gradients and other properties of the galaxies. We find mean stellar population gradients (negative Δ[Z/H]/log r gradient of − 0.285 ± 0.064; small positive Δlog(age)/log r gradient of +0.069 ± 0.049; and null Δ[E/Fe]/log r gradient of -0.008 ± 0.032), that are consistent with those of normal massive elliptical galaxies. However, we find a trend between metallicity gradients and velocity dispersion (with a negative slope of − 1.616 ± 0.539), that is not found for the most massive ellipticals. Furthermore, we find trends between the metallicity gradients and K-band luminosities (with a slope of 0.173 ± 0.081) as well as the distance from the BCG to the X-ray peak of the host cluster (with a slope of − 7.546 ± 2.752). The latter indicates a possible relation between the formation of the cluster and that of the central galaxy.

scholarly journals Did brightest cluster galaxies experience more than one star formation epoch?

2012 ◽  
Vol 8 (S295) ◽  
pp. 320-320
Author(s):  
D. N. Viljoen ◽  
S. I. Loubser
Keyword(s):  
Star Formation ◽  
Population Model ◽  
Stellar Population ◽  
Star Formation History ◽  
Full Spectrum ◽  
Cluster Galaxies ◽  
Brightest Cluster Galaxies ◽  
Formation History ◽  
Spectrum Fitting ◽  
Fitting Ability

AbstractWe use the full spectrum fitting ability of ULySS, with the Pegase.HR stellar population model to fit the observed spectra of 40 brightest cluster galaxies in order to determine whether a single or a composite stellar population provided the most probable representation of the star formation history (SFH). We find that some galaxies in the sample have more complex SFHs.

scholarly journals Stellar formation in Brightest Cluster Galaxies

2009 ◽  
Vol 5 (S262) ◽  
pp. 450-451
Author(s):  
Tatiana Zapata Pichinao ◽  
Gastão B. Lima Neto
Keyword(s):  
Star Formation ◽  
Stellar Population ◽  
External Source ◽  
Star Formation History ◽  
Dynamic State ◽  
X Ray ◽  
Cluster Galaxies ◽  
Brightest Cluster Galaxies ◽  
First Results ◽  
Low Metallicity

AbstractWe study the interplay between stellar population of the Brightest Cluster Galaxies (BCG) and cluster global properties. We use X-ray properties from Chandra, ROSAT and ASCA observations and BCGs spectra from SDSS-DR6. Using STARLIGHT we determined the star formation history of the BCGs and look for relations with the intra-cluster gas properties. Our first results show no correlation between the recent star formation with x-ray temperature and dynamic state. An important star formation is happening in cool-core Cluster. This new stellar population has low metallicity, pointing to an external source of cold gas to form stars.

scholarly journals Inverse stellar population age gradients of post-starburst galaxies at z = 0.8 with LEGA-C

2020 ◽  
Vol 497 (1) ◽  
pp. 389-404 ◽  
Author(s):  
Francesco D’Eugenio ◽  
Arjen van der Wel ◽  
Po-Feng Wu (吳柏锋) ◽  
Tania M Barone ◽  
Josha van Houdt ◽  
...  
Keyword(s):  
Star Formation ◽  
Stellar Population ◽  
Control Sample ◽  
Mass Range ◽  
Spatially Resolved ◽  
Star Formation Activity ◽  
Multiple Paths ◽  
High Fraction ◽  
Spatially Resolved Spectroscopy ◽  
Inside Out

ABSTRACT We use deep, spatially resolved spectroscopy from the Large Early Galaxy Astrophysics Census Survey to study radial variations in the stellar population of 17 spectroscopically selected post-starburst (PSB) galaxies. We use spectral fitting to measure two Lick indices, H δA and Fe 4383 , and find that, on average, PSB galaxies have radially decreasing H δA and increasing Fe 4383  profiles. In contrast, a control sample of quiescent, non-PSB galaxies in the same mass range shows outwardly increasing H δA and decreasing Fe 4383 . The observed gradients are weak (≈−0.2 Å/Re), mainly due to seeing convolution. A two-SSP (simple stellar population) model suggests that intrinsic gradients are as strong as observed in local PSB galaxies (≈−0.8 Å/Re). We interpret these results in terms of inside-out growth (for the bulk of the quiescent population) versus star formation occurring last in the centre (for PSB galaxies). At z ≈ 0.8, central starbursts are often the result of gas-rich mergers, as evidenced by the high fraction of PSB galaxies with disturbed morphologies and tidal features (40 per cent). Our results provide additional evidence for multiple paths to quiescence: a standard path, associated with inside-out disc formation and with gradually decreasing star formation activity, without fundamental structural transformation, and a fast path, associated with centrally concentrated starbursts, leaving an inverse age gradient and smaller half-light radius.

scholarly journals Observations across nearby spiral bulges

2007 ◽  
Vol 3 (S245) ◽  
pp. 141-142
Author(s):  
A. E. Sansom ◽  
S. I. Loubser ◽  
P. Sánchez-Blázquez ◽  
I. K. Söchting
Keyword(s):  
Stellar Population ◽  
Spiral Galaxies ◽  
Elliptical Galaxies ◽  
High Signal ◽  
Formation Mechanisms ◽  
Signal To Noise ◽  
Preliminary Results ◽  
Formation History ◽  
Larger Sample ◽  
Line Strengths

AbstractThe bulges of spiral galaxies may be old, as in our Galaxy, or may possess younger stars, as evidenced in spectroscopic line strengths in some external bulges. Bulges look similar to elliptical galaxies, but their formation history is expected to differ due to the presence of the disc and different formation mechanisms. This project extends the numbers of high signal-to-noise, broad coverage spectra to a larger sample of bulges in order to test conflicting ideas about their age distributions. New Gemini long-slit observations will be used to derive stellar population ages and histories across 30 bulges. Here we present preliminary results from the sample.

Sign in / Sign up

Export Citation Format

Share Document