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Articles 1 - 13 of 13
Full-Text Articles in Physical Sciences and Mathematics
Dynamical Masses Of Early-Type Galaxies: A Comparison To Lensing Results And Implications For The Stellar Initial Mass Function And The Distribution Of Dark Matter, J. Thomas, R. P. Saglia, R. Bender, D. Thomas, K. Gebhardt, J. Magorrian, E. M. Corsini, G. Wegner, S. Seitz
Dynamical Masses Of Early-Type Galaxies: A Comparison To Lensing Results And Implications For The Stellar Initial Mass Function And The Distribution Of Dark Matter, J. Thomas, R. P. Saglia, R. Bender, D. Thomas, K. Gebhardt, J. Magorrian, E. M. Corsini, G. Wegner, S. Seitz
Dartmouth Scholarship
This work aims to study the distribution of the luminous and dark matter in Coma early-type galaxies. Dynamical masses obtained under the assumption that mass follows light do not match with the masses of strong gravitational lens systems of similar velocity dispersions. Instead, dynamical fits with dark matter haloes are in good agreement with lensing results. We derive mass-to-light ratios of the stellar populations from Lick absorption line indices, reproducing well the observed galaxy colours. Even in dynamical models with dark matter haloes the amount of mass that follows the light increases more rapidly with the galaxy velocity dispersion than …
Colours Of Bulges And Discs Within Galaxy Clusters And The Signature Of Disc Fading On Infall, Michael J. Hudson, Jeffrey B. Stevenson, Russell J. Smith, Gary A. Wegner
Colours Of Bulges And Discs Within Galaxy Clusters And The Signature Of Disc Fading On Infall, Michael J. Hudson, Jeffrey B. Stevenson, Russell J. Smith, Gary A. Wegner
Dartmouth Scholarship
The origins of the bulge and disc components of galaxies are of primary importance to understanding galaxy formation. Here bulge–disc decomposition is performed simultaneously in B and R bands for 922 bright galaxies in eight nearby (z < 0.06) clusters with deep redshift coverage using photometry from the National Optical Astronomy Observatory (NOAO) Fundamental Plane Survey. The total galaxy colours follow a universal colour–magnitude relation (CMR). The discs of L* galaxies are 0.24 mag bluer in B−R than bulges. Bulges have a significant CMR slope while the CMR slope of discs is flat. Thus the slope of the CMR of the total light is driven primarily (60 per cent) by the bulge CMR, and to a lesser extent (40 per cent) by the change in the bulge‐to‐total ratio …
Dark Matter Scaling Relations And The Assembly Epoch Of Coma Early-Type Galaxies, J. Thomas, R. P. Saglia, R. Bender, D. Thomas, K. Gebhardt, J Magorrian, E. M. Corsini, G. Wegner
Dark Matter Scaling Relations And The Assembly Epoch Of Coma Early-Type Galaxies, J. Thomas, R. P. Saglia, R. Bender, D. Thomas, K. Gebhardt, J Magorrian, E. M. Corsini, G. Wegner
Dartmouth Scholarship
Axisymmetric, orbit-based dynamical models are used to derive dark matter scaling relations for Coma early-type galaxies. From faint to bright galaxies, halo core radii and asymptotic circular velocities increase. Compared to spirals of the same brightness, the majority of Coma early-type galaxies—those with old stellar populations—have similar halo core radii but more than two times larger asymptotic halo velocities. The average dark matter density inside 2 r eff decreases with increasing luminosity and is 6.8 times larger than in disk galaxies of the same B-band luminosity. Compared at the same stellar mass, dark matter densities in ellipticals are 13.5 …
Near Ultraviolet–Infrared Colours Of Red-Sequence Galaxies In Local Clusters, Timothy D. Rawle, Russell J. Smith, John R. Lucey, Michael J. Hudson, Gary A. Wegner
Near Ultraviolet–Infrared Colours Of Red-Sequence Galaxies In Local Clusters, Timothy D. Rawle, Russell J. Smith, John R. Lucey, Michael J. Hudson, Gary A. Wegner
Dartmouth Scholarship
We present GALEX near‐ultraviolet (NUV) and Two‐Micron All‐Sky Survey J‐band photometry for red‐sequence galaxies in local clusters. We define quiescent samples according to a strict emission threshold, removing galaxies with very recent star formation. We analyse the NUV–J colour–magnitude relation (CMR) and find that the intrinsic scatter is an order of magnitude larger than for the analogous optical CMR (∼0.35 rather than 0.05 mag), in agreement with previous studies. Comparing the NUV–J colours with spectroscopically derived stellar population parameters, we find a strong (>5.5σ) correlation with metallicity, only a marginal trend with …
Dynamical Modelling Of Luminous And Dark Matter In 17 Coma Early-Type Galaxies, J. Thomas, R. O. Saglia, R. Bender, D. Thomas, J K. Gebhardt, J. Magorrian, E. M. Corsini, G. Wegner
Dynamical Modelling Of Luminous And Dark Matter In 17 Coma Early-Type Galaxies, J. Thomas, R. O. Saglia, R. Bender, D. Thomas, J K. Gebhardt, J. Magorrian, E. M. Corsini, G. Wegner
Dartmouth Scholarship
Dynamical models for 17 early‐type galaxies in the Coma cluster are presented. The galaxy sample consists of flattened, rotating as well as non‐rotating early‐types including cD and S0 galaxies with luminosities between MB=−18.79 and −22.56. Kinematical long‐slit observations cover at least the major‐axis and minor‐axis and extend to 1–4reff. Axisymmetric Schwarzschild models are used to derive stellar mass‐to‐light ratios and dark halo parameters. In every galaxy, the best fit with dark matter matches the data better than the best fit without. The statistical significance is over 95 per cent for eight galaxies, around 90 per …
The Noao Fundamental Plane Survey - Iii. Variations In The Stellar Populations Of Red-Sequence Galaxies From The Cluster Core To The Virial Radius, Russell J. S. Smith, Michael J. Hudson, John R. Lucey, Jenica E. Nelan, Gary A. Wegner
The Noao Fundamental Plane Survey - Iii. Variations In The Stellar Populations Of Red-Sequence Galaxies From The Cluster Core To The Virial Radius, Russell J. S. Smith, Michael J. Hudson, John R. Lucey, Jenica E. Nelan, Gary A. Wegner
Dartmouth Scholarship
We analyse absorption line-strength indices for ~3000 red-sequence galaxies in 94 nearby clusters, to investigate systematic variations of their stellar content with location in the host cluster. The data are drawn from the NOAO Fundamental Plane Survey. Our adopted method is a generalization of that introduced by Nelan et al. to determine the global age-mass and metallicity-mass relations from the same survey. We find strong evidence for a change in galaxy properties, at fixed mass, over a range from the cluster centre to the virial radius, R_200. For example, red-sequence galaxies further out in the clusters have weaker Mgb5177 (at …
Noao Fundamental Plane Survey. Ii. Age And Metallicity Along The Red Sequence From Line‐Strength Data, Jenica E. Nelan, Russell J. Smith, Michael J. Hudson, Gary A. Wegner
Noao Fundamental Plane Survey. Ii. Age And Metallicity Along The Red Sequence From Line‐Strength Data, Jenica E. Nelan, Russell J. Smith, Michael J. Hudson, Gary A. Wegner
Dartmouth Scholarship
We present spectroscopic line-strength data for 4097 red-sequence galaxies in 93 low-redshift galaxy clusters and use these to investigate variations in average stellar populations as a function of galaxy mass. Our analysis includes an improved treatment of nebular emission contamination, which affects ~10% of the sample galaxies. Using the stellar population models of D. Thomas and collaborators, we simultaneously fit 12 observed line-strength-σ relations in terms of common underlying trends of age, [Z/H] (total metallicity), and [α/Fe] (α-element enhancement). We find that the observed line-strength-σ relations can be explained only if higher mass red-sequence galaxies are, on average, …
Regularized Orbit Models Unveiling The Stellar Structure And Dark Matter Halo Of The Coma Elliptical Ngc 4807, J. Thomas, R. P. Saglia, R. Bender, D. Thomas, K. Gebhardt, J. Magorrian, E. M. Corsini, G. Wegner
Regularized Orbit Models Unveiling The Stellar Structure And Dark Matter Halo Of The Coma Elliptical Ngc 4807, J. Thomas, R. P. Saglia, R. Bender, D. Thomas, K. Gebhardt, J. Magorrian, E. M. Corsini, G. Wegner
Dartmouth Scholarship
This is the second in a series of papers dedicated to unveiling the mass structure and orbital content of a sample of flattened early-type galaxies in the Coma cluster. The ability of our orbit libraries to reconstruct internal stellar motions and the mass composition of a typical elliptical in the sample is investigated by means of Monte Carlo simulations of isotropic rotator models. The simulations allow a determination of the optimal amount of regularization needed in the orbit superpositions. It is shown that under realistic observational conditions and with the appropriate regularization, internal velocity moments can be reconstructed to an …
Structural Properties Of Discs And Bulges Of Early-Type Galaxies, Roelof S. De Jong, Luc Simard, Roger L. Davies, R. P. Saglia, David Burstein, Matthew Colless, Robert Mcmahan, Gary Wegner
Structural Properties Of Discs And Bulges Of Early-Type Galaxies, Roelof S. De Jong, Luc Simard, Roger L. Davies, R. P. Saglia, David Burstein, Matthew Colless, Robert Mcmahan, Gary Wegner
Dartmouth Scholarship
We have used the EFAR sample of galaxies to investigate the light distributions of early-type galaxies. We decompose the two-dimensional light distribution of the galaxies in a flattened spheroidal component with a Sérsic radial light profile and an inclined disc component with an exponential light profile. We show that if we assume that all galaxies can have a spheroidal and a disc component, then the brightest, bulge-dominated elliptical galaxies have a fairly broad distribution in the Sérsic profile shape parameter nB, with a median of approximately 3.7 and with σ∼ 0.9. Other galaxies have smaller nB values. …
The Peculiar Motions Of Early-Type Galaxies In Two Distant Regions - Vi. The Maximum-Likelihood Gaussian Algorithm, M. Colless, R. P. Saglia, D. Burstein, R. L. Davies, R. K. Mcmahan, G. Wegner
The Peculiar Motions Of Early-Type Galaxies In Two Distant Regions - Vi. The Maximum-Likelihood Gaussian Algorithm, M. Colless, R. P. Saglia, D. Burstein, R. L. Davies, R. K. Mcmahan, G. Wegner
Dartmouth Scholarship
The EFAR project is designed to measure the properties and peculiar motions of early-type galaxies in two distant regions. Here we describe the maximum-likelihood algorithm we developed to investigate the correlations between the parameters of the EFAR data base. One-, two- and three-dimensional Gaussian models are constructed to determine the mean value and intrinsic spread of the parameters, and the slopes and intrinsic parallel and orthogonal spread of the Mg2–Mgb′,Mg2–σ,Mgb′–σ relations, and the Fundamental Plane. In the latter case, the cluster peculiar velocities are also determined. We show that this method is superior to …
The Peculiar Motions Of Early-Type Galaxies In Two Distant Regions -- Vii. Peculiar Velocities And Bulk Motions, Matthew Colless, R. P. Saglia, David Burstein, Roger L. Davies, Robert K. Mcmahan Jr, Gary Wegner
The Peculiar Motions Of Early-Type Galaxies In Two Distant Regions -- Vii. Peculiar Velocities And Bulk Motions, Matthew Colless, R. P. Saglia, David Burstein, Roger L. Davies, Robert K. Mcmahan Jr, Gary Wegner
Dartmouth Scholarship
We present peculiar velocities for 85 clusters of galaxies in two large volumes at distances between 6000 and 15 000 km s−1 in the directions of Hercules-Corona Borealis and Perseus-Pisces-Cetus (the EFAR sample). These velocities are based on Fundamental Plane (FP) distance estimates for early-type galaxies in each cluster. We fit the FP using a maximum likelihood algorithm which accounts for both selection effects and measurement errors, and yields FP parameters with smaller bias and variance than other fitting procedures. We obtain a best-fitting FP with coefficients consistent with the best existing determinations. We measure the bulk motions of …
The Peculiar Motions Of Early-Type Galaxies In Two Distant Rregions — Ii. The Spectroscopic Data, Gary Wegner, Matthew Colless, R. P. Saglia, Robert K. Mcmahan
The Peculiar Motions Of Early-Type Galaxies In Two Distant Rregions — Ii. The Spectroscopic Data, Gary Wegner, Matthew Colless, R. P. Saglia, Robert K. Mcmahan
Dartmouth Scholarship
We present the spectroscopic data for the galaxies studied in the EFAR project, which is designed to measure the properties and peculiar motions of early-type galaxies in two distant regions. We have obtained 1319 spectra of 714 early-type galaxies over 33 observing runs on 10 different telescopes. We describe the observations and data reductions used to measure redshifts, velocity dispersions and the Mgb and Mg2 Lick linestrength indices. Detailed simulations and intercomparison of the large number of repeat observations lead to reliable error estimates for all quantities. The measurements from different observing runs are calibrated to a common …
The Peculiar Motions Of Early-Type Galaxies In Two Distant Regions -- V. The Mg-- Relation, Age And Metallicity, M. Colless, D. Burstein, R. L. Davies, R. K. Mcmahan, R. P. Saglia, G. Wegner
The Peculiar Motions Of Early-Type Galaxies In Two Distant Regions -- V. The Mg-- Relation, Age And Metallicity, M. Colless, D. Burstein, R. L. Davies, R. K. Mcmahan, R. P. Saglia, G. Wegner
Dartmouth Scholarship
We have examined the Mg—σ relation for early-type galaxies in the EFAR sample and its dependence on cluster properties. A comprehensive maximum likelihood treatment of the sample selection and measurement errors gives fits to the global Mg—σ relation of Mg b′=0.131 log σ −0.131 and Mg2=0.257 log σ −0.305. The slope of these relations is 25 per cent steeper than that obtained by most other authors owing to the reduced bias of our fitting method. The intrinsic scatter in the global Mg— σ relation is estimated to be 0.016 mag in Mg b′ and 0.023 …