Dark Matter and Elliptical Galaxy Dynamics

2009 ◽  
Vol 5 (H15) ◽  
pp. 65-65
Author(s):  
Ortwin Gerhard
Keyword(s):  
Dark Matter ◽  
Angular Momentum ◽  
Momentum Distribution ◽  
Elliptical Galaxy ◽  
Elliptical Galaxies ◽  
Galaxy Dynamics ◽  
Formation And Evolution

The halos of elliptical galaxies, through their orbit and angular momentum distribution, contain important information about the formation and evolution of these systems.

scholarly journals Properties of Dark Matter Halos in Disk Galaxies

2004 ◽  
Vol 220 ◽  
pp. 281-286 ◽  
Author(s):  
Roelof S. de Jong ◽  
Susan Kassin ◽  
Eric F. Bell ◽  
Stéphane Courteau
Keyword(s):  
Dark Matter ◽  
Angular Momentum ◽  
Momentum Distribution ◽  
Surface Brightness ◽  
High Surface ◽  
Large Set ◽  
Dark Matter Halos ◽  
Rotation Curves ◽  
Galaxy Assembly ◽  
Adiabatic Contraction

We present a simple technique to estimate mass-to-light (M/L) ratios of stellar populations based on two broadband photometry measurements, i.e. a colour-M/L relation. We apply the colour-M/L relation to galaxy rotation curves, using a large set of galaxies that span a great range in Hubble type, luminosity and scale size and that have accurately measured HI and/or Hα rotation curves. Using the colour-M/L relation, we construct stellar mass models of the galaxies and derive the dark matter contribution to the rotation curves.We compare our dark matter rotation curves with adiabatically contracted Navarro, Frenk, & White (1997, NFW hereafter) dark matter halos. We find that before adiabatic contraction most high surface brightness galaxies and some low surface brightness galaxies are well fit by a NFW dark matter profile. However, after adiabatic contraction, most galaxies are poorly fit in the central few kpc. the observed angular momentum distribution in the baryonic component is poorly matched by ACDM model predictions, indicating that the angular momentum distribution is not conserved during the galaxy assembly process. We find that in most galaxies the dark matter distribution can be derived by scaling up the HI gas contribution. However, we find no consistent value for the scaling factor among all the galaxies.

scholarly journals A Model for the Sequence of Elliptical Galaxies

1987 ◽  
Vol 117 ◽  
pp. 367-367
Author(s):  
Rosemary F. G. Wyse ◽  
Bernard J. T. Jones
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Initial Conditions ◽  
Elliptical Galaxy ◽  
Elliptical Galaxies ◽  
Density Fluctuations ◽  
Analytic Approximation ◽  
Non Linear

We present a simple model for the formation of elliptical galaxies, based on a binary clustering hierarchy of dark matter, the chemical enrichment of the gas at each level being controlled by supernovae. The initial conditions for the non-linear phases of galaxy formation are set by the post-recombination power spectrum of density fluctuations. We investigate two models for this power spectrum - the first is a straightforward power law, |δk|2 ∝ kn, and the second is Peeble's analytic approximation to the emergent spectrum in a universe dominated by cold dark matter. The normalisation is chosen such that on some scale, say M ∼ 1012M⊙, the objects that condense out have properties - radius and velocity dispersion - resembling ‘typical’ galaxies. There is some ambiguity in this due to the poorly determined mass-to-light ratio of a typical elliptical galaxy — we look at two normalisations, σ1D ∼ 350kms−1 and σ1D ∼ 140kms−1. The choice determines which of Compton cooling or hydrogen cooling is more important during the galaxy formation period. The non-linear behaviour of the perturbations is treated by the homogeneous sphere approximation.

The Angular Momentum Distribution of Gas and Dark Matter in Galactic Halos

2005 ◽  
Vol 628 (1) ◽  
pp. 21-44 ◽  
Author(s):  
Sanjib Sharma ◽  
Matthias Steinmetz
Keyword(s):  
Dark Matter ◽  
Angular Momentum ◽  
Momentum Distribution ◽  
Galactic Halos

scholarly journals Angular Momentum Growth around Local Density Maxima

1988 ◽  
Vol 130 ◽  
pp. 552-552
Author(s):  
A. F. Heavens ◽  
J. A. Peacock
Keyword(s):  
Dark Matter ◽  
Angular Momentum ◽  
Power Spectrum ◽  
Total Angular Momentum ◽  
Cold Dark Matter ◽  
Local Density ◽  
Probability Distributions ◽  
Power Spectra ◽  
Elliptical Galaxies ◽  
Angular Momenta

We have calculated the growth of angular momentum about local density maxima at early epochs. We find that high peaks experience higher torques than low peaks, counteracting the short collapse time during which the high peaks can acquire angular momentum. Which effect is dominant depends on the perturbation power spectrum: for power spectra characteristic of both cold dark matter and hot dark matter, the effects nearly cancel, and the total angular momentum acquired by a collapsing object is almost independent of the height of the peak. Furthermore, the distributions of angular momenta acquired by collapsing protosystems are extremely broad, for all power spectra, far exceeding any modest differences between peaks of different height.These results indicate that it is not possible to account for the systematic differences in angular momentum properties of disk and elliptical galaxies simply by postulating that the latter arise from fluctuations of greater overdensity, contrary to some recent suggestions. The figure shows the probability distributions for the final angular momentum acquired by peaks of dimensionless height 1–4, for a power spectrum similar to cold dark matter. A fuller account of this work has been submitted to MNRAS.

Models for the Formation and Evolution of Spherical Galaxies

1974 ◽  
Vol 58 ◽  
pp. 191-194
Author(s):  
Richard B. Larson
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
Stellar Evolution ◽  
Elliptical Galaxy ◽  
Elliptical Galaxies ◽  
Dynamical Model ◽  
Model Calculations ◽  
Formation And Evolution

Detailed dynamical model calculations based on a conventional collapse picture of galaxy formation, and conventional assumptions concerning star formation and stellar evolution, are found to be able to reproduce satisfactorily the basic structural and photometric properties of elliptical galaxies. The quasar phenomenon may be identifiable with the formation of the nucleus of a giant elliptical galaxy.

scholarly journals Building Galactic Disks in Triaxial Dark Matter Halos

2006 ◽  
Vol 2 (S235) ◽  
pp. 24-28
Author(s):  
Isaac Shlosman
Keyword(s):  
Dark Matter ◽  
Angular Momentum ◽  
Star Formation ◽  
Numerical Simulations ◽  
Recent Work ◽  
Stellar Evolution ◽  
Dark Matter Halos ◽  
Local Universe ◽  
Broad Agreement ◽  
Formation And Evolution

AbstractWe review our recent work on the formation and evolution of disks within triaxial dark matter (DM) halos by means of numerical simulations, including star formation and feedback from stellar evolution. The growing disks are strongly influenced by shapes of DM halos and modify them in turn. Disk parameters are in a broad agreement with those in the local universe. Gas-rich stellar bars grow in tandem with the disk and facilitate the angular momentum redistribution in the system and radial gas inflow. Nested bars appear to form as a by-product. Interactions between various non-axisymmetric components—bars, disks and halos lead to decay of bars or washing out of ellipticity in the inner halo.

scholarly journals Formation and Evolution of Disk Galaxies

1999 ◽  
Vol 183 ◽  
pp. 153-153
Author(s):  
C. Firmani ◽  
V. Avila-Reese
Keyword(s):  
Dark Matter ◽  
Angular Momentum ◽  
Power Spectrum ◽  
Mass Velocity ◽  
Dark Matter Halo ◽  
Stellar Disk ◽  
Physical Factors ◽  
Disk Galaxies ◽  
Velocity Relation ◽  
Formation And Evolution

We have developed a semianalitical approach to study galaxy formation and evolution in the cosmological context. Disk galaxies (dark matter halo+luminous disk) are considered to be formed through an extended process of gravitational collapse, whose character is determined by the statistical properties of the density fluctuation field assumed here to be Gaussian. Gas disks in centrifugal equilibrium within the collapsing dark halos are built up (detailed angular momentum conservation is assumed), and their galactic evolution is calculated with a model which consider all the gravitational interactions, the hydrodynamics of the ISM, and the SF process. A bulge as product of stellar disk gravitational instabilities is constructed. To study general behaviors a Gaussian σ8 = 1 SCDM model is used. For a given mass one obtains a range of dark matter configurations. The average case is in excellent agreement with results of cosmological N-body simulations. The slope of the mass-velocity relation agrees with the slope of the H- and I-band Tully-Fisher relations, but the velocities are too high. This problem dissapears if the power spectrum is renormalized to σ8 = 0.57, suggesting that the TF relation is result of the natural extension to galactic scales of the galaxy distribution power spectrum, and that on the basis of its origin are the cosmological initial conditions. The scatter on the mass-velocity relation is realistic. The models predict disk exponential surface brightness (SB) profiles, nearly flat rotation curves, and negative radial gradients in the B-V color. The obtained, gas fractions, B-V colors, central SBs μB0, bulge-to-disk (b/d) ratios, and rotation velocities (for σ8 = 0.57) are in agreement with observations, and their correlations are similar to those which define the Hubble sequence, including the LSB galaxies. These properties and correlations are the product of the combination of three fundamental physical factors: the mass, the mass aggregation history (MAH), and the initial angular momentum. The intensive properties are almost invariant to the mass, the MAH determines the B-V color, and the spin parameter λ mainly influences on μB0, and b/d ratio.

scholarly journals Shells and the Potential Wells of Elliptical Galaxies

1987 ◽  
Vol 127 ◽  
pp. 249-259
Author(s):  
P.J. Quinn ◽  
Lars Hernquist
Keyword(s):  
Dark Matter ◽  
Large Range ◽  
Elliptical Galaxy ◽  
Elliptical Galaxies ◽  
Potential Well ◽  
Potential Wells ◽  
Shell System ◽  
History Of

A survey of the possible variety of sharp-edged, caustic features that may arise in the collision of galaxies with very different masses and sizes (Hernquist and Quinn 1986a) has shown that in general shells are morphologically very complex. It is therefore not easy to determine the history of the collision that produced the shells nor the properties of the galaxies involved. However, a small number of shell galaxies (notably NGC 3923) have a sufficiently simple and orderly shell distribution that we believe the shells were formed by a chance very symmetric and simple encounter. In such cases we are presented with a unique opportunity to investigate the potential well of an elliptical galaxy over a large range in radius (≃ 0.5re − 20re). An analysis of the NGC 3923 shell system (Hernquist and Quinn 1986b) has shown that a large amount of dark matter is present (Mdark≃ 40Mluminous, r < 17re).

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