scholarly journals Line-Strength Profiles in Early-Type Galaxies

1995 ◽  
Vol 164 ◽  
pp. 453-453
Author(s):  
David Fisher ◽  
Garth Illingworth ◽  
Marijn Franx
Keyword(s):  
Stellar Population ◽  
Velocity Dispersion ◽  
Line Strength ◽  
Strong Correlations ◽  
Metal Line ◽  
Cluster Galaxies ◽  
Brightest Cluster Galaxies ◽  
The Mean ◽  
S0 Galaxies ◽  
Line Strengths

Line-strengths and their gradients in Mg, Fe, and Hβ have been determined for a sample of 9 brightest cluster (BCG), 7 elliptical, and 15 S0 galaxies in order to study their stellar populations and investigate their relationship to one another. We find that BCGs follow the same relationship between central Mgb line-strength and central velocity dispersion found for ellipticals while the S0 galaxies show significant scatter with respect to this relation. Brightest cluster galaxies are in agreement with the known trend towards more massive ellipticals having larger [Mg/Fe] ratios while the internal gradients within our BCG and E galaxies are consistent with a roughly constant [Mg/Fe] ratio. We find that a correlation exists between the central [Mg/Fe] ratio and average Hβ line-strength in the sense that BCG and E galaxies with larger [Mg/Fe] ratios have lower Hβ strengths. For our BCG and E galaxies, Hβ is the best predictor of [Mg/Fe] ratio. The Mgb metallicity gradients for BCGs and ellipticals are similar and consistent with a reduction in the mean metallicity of the stellar population by about a factor of 2 over a factor of ten in radius. No strong correlations are found between the metallicity gradient sizes and either kinematic or line-strength parameters of the E and BCG galaxies. The S0 disks display roughly constant Mg, Fe, and Hβ line-strengths with radius indicating that they have uniform age and metallicity throughout. S0 galaxy minor axes ‘bulge’ metal line-strength gradients are similar to elliptical gradients and fall to values lower than those found in the disks.

scholarly journals Properties of E & S0 Galaxies in the Coma Cluster

1996 ◽  
Vol 171 ◽  
pp. 419-419
Author(s):  
Dörte Mehlert ◽  
Ralf Bender ◽  
Roberto Saglia ◽  
Gary Wegner ◽  
Inger Jørgensen
Keyword(s):  
Kinetic Energy ◽  
Stellar Population ◽  
Velocity Dispersion ◽  
Low Density ◽  
Coma Cluster ◽  
Measured Velocity ◽  
The Mean ◽  
Velocity Dispersions ◽  
S0 Galaxies ◽  
Mean Kinetic Energy

As one of the richest nearby clusters, Coma is the ideal place to study the structure of galaxies as a function of environmental density, thus to constrain the theories of galaxy formation and evolution. For a magnitude limited sample of ≈ 40 E and S0 galaxies we want to obtain spectra with sufficient S/N and spatial resolution, that we can derive the rotation curves, the velocity dispersions profiles and the radial gradients of the line indices of Mg, Fe and Hβ. Following questions will be addressed: •Are the radial velocity dispersion profiles and the rotation of galaxies in high density environments similar to those in low density environments? Data for galaxies in low density environment are available from Bender et al. (1994, MNRAS, 269, 785). Are the centrally measured velocity dispersions representative for the mean kinetic energy of the galaxy?•Can the scatter in the Fundamental Plane (FP) - which tightly correlates the radii, surface brightnesses and (central) velocity dispersions (Djorgovski & Davis, 1987, ApJ, 313, 59; Dressier et al. 1987, ApJ, 313, 42) - for the Coma cluster be reduced if the mean kinetic energy is used instead of the central velocity dispersion? Can we derive stronger constraint on the variations in the M/L ratio than already implied by the FP?•The radial gradients of the line indices can be used to test the hypothesis that the metallicity gradient depends on the so-called “escape velocity” of the stars introduced by Franx & Illingworth (1990, ApJ, 359, L41). Also we can check whether the age of the stellar population varies with radius. Ages and metallicities can be estimated from the data with the use of stellar population models (Worthey 1994, ApJS, 95, 105; Bruzual & Chariot 1993, ApJ, 405, 538).•How does the radial variation of stellar populations and kinematics within the galaxies vary as a function of the clusters density profile?

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 The Galactic Neighbourhood

1978 ◽  
Vol 79 ◽  
pp. 71-91 ◽  
Author(s):  
G. A. Tammann ◽  
R. Kraan
Keyword(s):  
Luminosity Function ◽  
Velocity Dispersion ◽  
Radial Component ◽  
Virgo Cluster ◽  
Cluster Centre ◽  
Different Types ◽  
Peculiar Motion ◽  
The Mean ◽  
S0 Galaxies ◽  
Hubble Flow

Several properties of the 131 galaxies known within 9. 1 Mpc are investigated. 88 of these galaxies are concentrated into eight groups, leaving 33 percent of true field galaxies. There are E/S0 and S0 galaxies among the field galaxies; their types must be of cosmogonic origin. the groups have small velocity dispersion which limits the mean mass-to-light ratio for the different types of group galaxies to m/L < 20. Within the supergalactic plane the deviation from an ideal Hubble flow are small: the changes of ΔHO/<HO> with distance and direction are not larger than ten percent; the radial component of the peculiar motion of field galaxies is <25 km s−1. the differential luminosity function of S/Im galaxies is well approximated by a Gaussian with and . the luminosity function of E/S0 galaxies is much flatter with a possible minimum, separating true E's and dwarf ellipticals (Reaves, 1977). the sample galaxies are strongly concentrated toward the supergalactic plane; at a distance of 4 Mpc of the plane the luminosity density drops to half its value. There is also a pronounced luminosity density decrease with increasing distance from the Virgo cluster centre; at a distance of 30 Mpc the density has decreased by more than a factor of 104. the best estimate of the mean luminosity density within a sphere of 30 Mpc radius centered on the Virgo cluster is 1.5 · 108 L⊙ Mpc−3.

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 (&lt;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 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 Shapes and alignments of dark matter haloes and their brightest cluster galaxies in 39 strong lensing clusters

2020 ◽  
Vol 496 (3) ◽  
pp. 2591-2604 ◽  
Author(s):  
Taizo Okabe ◽  
Masamune Oguri ◽  
Sébastien Peirani ◽  
Yasushi Suto ◽  
Yohan Dubois ◽  
...  
Keyword(s):  
Dark Matter ◽  
Gravitational Lensing ◽  
Hubble Space Telescope ◽  
Mean Value ◽  
Cluster Galaxies ◽  
Brightest Cluster Galaxies ◽  
Strong Lensing ◽  
The Mean ◽  
The Difference ◽  
Massive Clusters

ABSTRACT We study shapes and alignments of 45 dark matter (DM) haloes and their brightest cluster galaxies (BCGs) using a sample of 39 massive clusters from Hubble Frontier Field (HFF), Cluster Lensing And Supernova survey with Hubble (CLASH), and Reionization Lensing Cluster Survey (RELICS). We measure shapes of the DM haloes by strong gravitational lensing, whereas BCG shapes are derived from their light profiles in Hubble Space Telescope images. Our measurements from a large sample of massive clusters presented here provide new constraints on DM and cluster astrophysics. We find that DM haloes are on average highly elongated with the mean ellipticity of 0.482 ± 0.028, and position angles of major axes of DM haloes and their BCGs tend to be aligned well with the mean value of alignment angles of 22.2 ± 3.9 deg. We find that DM haloes in our sample are on average more elongated than their BCGs with the mean difference of their ellipticities of 0.11 ± 0.03. In contrast, the Horizon-AGN cosmological hydrodynamical simulation predicts on average similar ellipticities between DM haloes and their central galaxies. While such a difference between the observations and the simulation may well be explained by the difference of their halo mass scales, other possibilities include the bias inherent to strong lensing measurements, limited knowledge of baryon physics, or a limitation of cold DM.

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.

Line Strengths and Line-Strength Gradients in S0 Galaxies

1996 ◽  
Vol 459 ◽  
pp. 110 ◽  
Author(s):  
David Fisher ◽  
Marijn Franx ◽  
Garth Illingworth
Keyword(s):  
Line Strength ◽  
S0 Galaxies ◽  
Line Strengths

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.

Sign in / Sign up

Export Citation Format

Share Document