scholarly journals Integrated Ultraviolet Spectra and Line Indices of M31 Globular Clusters and the Cores of Elliptical Galaxies

1998 ◽  
Vol 116 (5) ◽  
pp. 2297-2314 ◽  
Author(s):  
Jerry M. Ponder ◽  
David Burstein ◽  
Robert W. O'Connell ◽  
James A. Rose ◽  
Jay A. Frogel ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Elliptical Galaxies ◽  
Ultraviolet Spectra

scholarly journals Variable Stars in Dwarf Spheroidal Galaxies

1973 ◽  
Vol 21 ◽  
pp. 35-48
Author(s):  
Steven Van Agt
Keyword(s):  
Globular Clusters ◽  
Local Group ◽  
Elliptical Galaxies ◽  
Variable Stars ◽  
Dwarf Spheroidal Galaxies ◽  
Theoretical Predictions ◽  
History Of ◽  
Set Up ◽  
Theoretical Considerations ◽  
Spheroidal Galaxies

Interest in dwarf spheroidal galaxies is motivated by a number of reasons; an important one on the occasion of this colloquium is the abundance of variable stars. The theory of stellar evolution and stellar pulsations is now able to predict from theoretical considerations characteristic properties of variable stars in the colour-magnitude diagram (Iben, 1971). By observing the variable stars in the field, and in as wide a selection of objects as possible, more insight can be obtained into the history of the oldest members of our Galaxy (the globular clusters) and of the dwarf spheroidal galaxies in the Local Group. It is worthwhile to explore the spheroidal galaxies as observational tests for the theoretical predictions of conditions in space away from our Galaxy. The numbers of variable stars in the dwarf spheroidal galaxies are such that we may expect well-defined relations to emerge once reliable magnitude sequences have been set up, the variable stars found, and their periods determined. Six dwarf spheroidal galaxies are presently known in the Local Group within a distance of 250 kpc. In Table I, which lists members of the Local Group, they are at the low-luminosity end of the sequence of elliptical galaxies (van den Bergh, 1968).

The Effect of Neutrinos on the Formation Time of Rich Clusters of Galaxies

1981 ◽  
Vol 4 (2) ◽  
pp. 181-182 ◽  
Author(s):  
B. M. Lewis
Keyword(s):  
Globular Clusters ◽  
Relaxation Mechanism ◽  
Elliptical Galaxies ◽  
Formation Time ◽  
Clusters Of Galaxies ◽  
Cluster Mass ◽  
Cluster Of Galaxies ◽  
Universal Expansion ◽  
Hubble Time

Both the radial and the velocity distributions of galaxies within rich clusters are well described by the isothermal distribution (e.g. Lewis 1978 and 1979). It is tempting to ascribe this apparently relaxed state to the operation of Lynden-BeU’s (1967) violent relaxation mechanism, during the initial coherent collapse on the proto-cluster, after it brakes itself against the universal expansion. This scenario explains the isothermal distribution observed in elliptical galaxies and globular clusters. When applied to a cluster of galaxies made up of baryons, however, the timescale for the scenario is comparable with the Hubble time H−1. The situation changes if most of the cluster mass is contributed by neutrinos.

scholarly journals On the Dynamical Evolution of Clusters of Galaxies

1978 ◽  
Vol 79 ◽  
pp. 357-375 ◽  
Author(s):  
Jeremiah P. Ostriker
Keyword(s):  
Globular Clusters ◽  
Normal Modes ◽  
Dynamical Evolution ◽  
Second Law Of Thermodynamics ◽  
Elliptical Galaxies ◽  
Second Law ◽  
Clusters Of Galaxies ◽  
Physical Processes ◽  
Rotating Systems ◽  
Accurate Picture

The theory of the dynamics of star clusters (cf. Spitzer 1975 for a review) is by now so well developed that we have, or think we have, a moderately accurate picture of the physical processes acting in and the overall evolution of spherical systems. in contrast, flattened and/or rotating systems are apparently subject to a variety of ill-understood instabilities which ultimately are a manifestation of the second law of thermodynamics; at given total energy, a system will tend to increase the fraction of its kinetic energy in disordered rather than ordered form. But spherical systems (globular clusters, elliptical galaxies, Morgan cD clusters of galaxies) are relatively smooth and featureless; they show little substructure indicating, presumably, that they are quite stable to perturbations of their fundamental normal modes, and they are normally modeled as rather “hot”, pressure supported systems.

scholarly journals GMOS Spectroscopy of Globular Clusters in Dwarf Elliptical Galaxies

2007 ◽  
Vol 3 (S246) ◽  
pp. 429-430
Author(s):  
Bryan W. Miller ◽  
Jennifer Lotz ◽  
Michael Hilker ◽  
Markus Kissler-Patig ◽  
Thomas Puzia
Keyword(s):  
Globular Clusters ◽  
Milky Way ◽  
Elliptical Galaxies ◽  
Preliminary Results ◽  
Dwarf Elliptical Galaxies ◽  
Milky Way Halo

AbstractWe present a Gemini/GMOS program to measure spectroscopic metallicities and ages of globular clusters (GCs) and nuclei in dwarf elliptical galaxies in the Virgo and Fornax Clusters. Preliminary results indicate that the globular clusters are old and metal-poor, very similar to the GCs in the Milky Way halo. The nuclei tend to be more metal-rich than the globular clusters but more metal-poor and older, on average, than the stars in the bodies of the galaxies. The [α/Fe] ratio appears to be solar for the GCs, nuclei, and dEs, but the uncertainties do not exclude some globular clusters from being enhanced in alpha elements.

scholarly journals Tidal Effects on Spherical Stellar Systems

1975 ◽  
Vol 69 ◽  
pp. 53-55
Author(s):  
D. W. Keenan ◽  
K. A. Innanen
Keyword(s):  
Internal Structure ◽  
Globular Clusters ◽  
Elliptical Galaxies ◽  
Star Cluster ◽  
Stellar Systems ◽  
Tidal Effects ◽  
Dwarf Elliptical Galaxies

Many self-gravitating stellar systems are satellites of larger galaxies and must therefore be subjected to the tidal field of the parent system. Examples are the globular clusters and dwarf elliptical galaxies, which are satellites of our Galaxy. Most previous studies of tidal effects have been highly simplified, e.g. clusters in circular planar galactic orbits (Bok, 1934), or have assumed that the tidal field acts to limit the size of a star cluster without any effects on its internal structure or stability (Spitzer and Shapiro, 1972; Spitzer and Thuan, 1972).

scholarly journals The Formation and Evolution of Star Clusters and Galaxies

2005 ◽  
Vol 13 ◽  
pp. 347-349
Author(s):  
Stephen E. Zepf
Keyword(s):  
Galaxy Formation ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Near Infrared ◽  
Cluster Formation ◽  
Star Clusters ◽  
Elliptical Galaxies ◽  
Cluster Systems ◽  
Important Observation ◽  
Formation And Evolution

AbstractThis paper addresses the questions of what we have learned about how and when dense star clusters form, and what studies of star clusters have revealed about galaxy formation and evolution. One important observation is that globular clusters are observed to form in galaxy mergers and starbursts in the local universe, which both provides constraints on models of globular cluster formation, and suggests that similar physical conditions existed when most early-type galaxies and their globular clusters formed in the past. A second important observation is that globular cluster systems typically have bimodal color distributions. This was predicted by merger models, and indicates an episodic formation history for elliptical galaxies. A third and very recent result is the discovery of large populations of intermediate age globular clusters in several elliptical galaxies through the use of optical to near-infrared colors. These provide an important link between young cluster systems observed in starbursts and mergers and old cluster systems. This continuum of ages of the metal-rich globular cluster systems also indicates that there is no special age or epoch for the formation of the metal-rich globular clusters, which comprise about half of the cluster population. The paper concludes with a brief discussion of recent results on the globular cluster – low-mass X-ray binary connection.

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