scholarly journals Disks Controlling Chaos in a 3D Dynamical Model for Elliptical Galaxies

2011 ◽  
Vol 20 (1) ◽  
Author(s):  
Euaggelos E. Zotos
Keyword(s):  
Phase Plane ◽  
Elliptical Galaxy ◽  
Elliptical Galaxies ◽  
Dynamical Model ◽  
Dynamical Parameter ◽  
Secondary Resonances ◽  
Homogeneous Core ◽  
2D System ◽  
New Phase ◽  
Disk Component

AbstractA 3D dynamical model with a quasi-homogeneous core and a disk component is used for the chaos control in the central parts of elliptical galaxy. Numerical experiments in the 2D system show a very complicated phase plane with a large chaotic sea, considerable sticky layers and a large number of islands, produced by secondary resonances. When the mass of the disk increases, the chaotic regions decrease gradually, and, finally, a new phase plane with only regular orbits appears. This evolution indicates that disks in elliptical galaxies can act as the chaos controllers. Starting from the results obtained in the 2D system, we locate the regions in the phase space of the 3D system, producing regular and chaotic orbits. For this we introduce and use a new dynamical parameter, the S(w) spectrum, which proves to be useful as a fast indicator and allows us to distinguish the regular motion from chaos in the 3D potentials. Other methods for detecting chaos are also discussed.

scholarly journals A New Dynamical Parameter for the Study of Sticky Orbits in a 3D Galactic Model

2011 ◽  
Vol 20 (3) ◽  
Author(s):  
Euaggelos E. Zotos
Keyword(s):  
Dynamical System ◽  
Classical Method ◽  
Elliptical Galaxy ◽  
Dynamical Model ◽  
Dynamical Parameter ◽  
2D System ◽  
Galactic Model ◽  
Dense Nucleus

AbstractA 3D dynamical model is used to study the motion in the central parts of an elliptical galaxy, hosting a massive and dense nucleus. Our aim is to investigate the regular or chaotic character of the motion, with emphasis in the different chaotic components, as well as the sticky regions of the dynamical system. In order to define the character of the motion in the 2D system, we use the classical method of the Poincaré x − p

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 9.2. Cores or cusps in elliptical galaxies: luminosity or environment?

1998 ◽  
Vol 184 ◽  
pp. 385-386
Author(s):  
Roelof S. de Jong ◽  
Roger L. Davies ◽  
Robert F. Minchin ◽  
John R. Lucey ◽  
James Steel
Keyword(s):  
Elliptical Galaxies ◽  
Steep Slope ◽  
Physical Variable ◽  
Stellar Disk ◽  
Heterogeneous Sample ◽  
Luminous Galaxies ◽  
End Products ◽  
Disk Component ◽  
Ultimate Nature

Two classes of elliptical galaxies are now recognised (Kormendy & Bender 1996). Luminous ellipticals rotate slowly (Davies et al. 1983and tend to have boxy isophotes. Ellipticals fainter than L∗ exhibit an increasing tendency to be rotationally supported and to possess a stellar disk component. This dichotomy led Bender, Burstein & Faber (1992) to suggest that the physical variable that controls the ultimate nature of a forming galaxy is the degree of gaseous dissipation that occurs in the final merger it experiences. Low luminosity systems experience more dissipative mergers which generate high rotation, disky end products. As bigger galaxies are formed, the mergers become increasingly stellar, producing the classical slow rotating ellipticals. They termed this the gas/stellar continuum. This global dichotomy is also reflected in the bimodality of core morphologies of the heterogeneous sample of local ellipticals observed with HST. The low luminosity disky galaxies have ‘hard’ cores with a steep slope in the luminosity profile at small radii, whereas the luminous galaxies have ‘soft’ cores with flat profiles at small radii (e.g. Faber et al. 1997).

Elliptical Galaxies—Getting to the Heart

1990 ◽  
Vol 8 (3) ◽  
pp. 238-242
Author(s):  
Elaine M. Sadler
Keyword(s):  
Optical Properties ◽  
Elliptical Galaxy ◽  
Elliptical Galaxies ◽  
Radio Sources ◽  
Powerful Radio

AbstractElliptical galaxies are at first sight a remarkably homogenous class of objects, yet some of them produce large and enormously powerful radio sources while others remain more or less quiescent. Why should this be so? What prompts the nucleus of an elliptical galaxy to become ‘active’? What, if anything, do elliptical galaxies have in common with the bulges of spirals? Here, I review some of the radio and optical properties of nearby elliptical galaxies, with special emphasis on events which take place within the central kiloparsec.

Dual Stellar Halos in Early-type Galaxies and Formation of Massive Galaxies

2015 ◽  
Vol 11 (S317) ◽  
pp. 253-258
Author(s):  
Myung Gyoon Lee ◽  
In Sung Jang
Keyword(s):  
Strong Evidence ◽  
Elliptical Galaxy ◽  
Elliptical Galaxies ◽  
Early Type ◽  
Massive Galaxies ◽  
Mode Formation

AbstractM105 in the Leo I Group is a textbook example of a standard elliptical galaxy. It is only one of the few elliptical galaxies for which we can study their stellar halos using the resolved stars. It is an ideal target to study the structure and composition of stellar halos in elliptical galaxies. We present photometry and metallicity of the resolved stars in the inner and outer regions of M105. These provide strong evidence that there are two distinct stellar halos in this galaxy, a metal-poor (blue) halo and a metal-rich (red) halo. Then we compare them with those in other early-type galaxies and use the dual halo mode formation scenario to describe how massive galaxies formed.

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.

Constraints on Elliptical Galaxy Formation from Dry Mergers

2006 ◽  
Vol 2 (S235) ◽  
pp. 195-195
Author(s):  
Julia M. Comerford ◽  
Eliot Quataert ◽  
Chung-Pei Ma
Keyword(s):  
Galaxy Formation ◽  
Elliptical Galaxy ◽  
Elliptical Galaxies ◽  
Analytic Model ◽  
Dark Matter Halos ◽  
Early Type ◽  
Mass Assembly ◽  
Minor Mergers ◽  
Analytic Models

Recent observations suggest that dissipationless mergers of elliptical galaxies build up the population of massive early-type galaxies (Bell et al. 2004; Faber et al. 2006). This type of merger is observed in galaxy clusters (Tran et al. 2005) and predicted by semi-analytic models which find mass assembly times significantly later than star-formation times for the most massive elliptical galaxies (de Lucia & Blaizot 2006). Here, we use a semi-analytic model of minor mergers of dark matter halos to examine the role of dry minor mergers in elliptical galaxy formation.

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