scholarly journals Masses and M/L Ratios of Bright Globular Clusters in NGC 5128

2007 ◽  
Vol 3 (S246) ◽  
pp. 418-422
Author(s):  
M. Rejkuba ◽  
P. Dubath ◽  
D. Minniti ◽  
G. Meylan
Keyword(s):  
Globular Clusters ◽  
Velocity Dispersion ◽  
Local Group ◽  
Structural Parameters ◽  
Elliptical Galaxy ◽  
Radial Velocities ◽  
Velocity Dispersions ◽  
The Masses ◽  
Massive Clusters ◽  
Centaurus A

AbstractWe present an analysis of the radial velocities and velocity dispersions for 27 bright globular clusters in the nearby elliptical galaxy NGC 5128 (Centaurus A). For 22 clusters we combine our new velocity dispersion measurements with the information on the structural parameters, either from the literature when available or from our own data, in order to derive the cluster masses and mass-to-light (M/L) ratios. The masses range from 1.2 × 105M⊙, typical of Galactic globular clusters, to 1.4 × 107M⊙, similar to more massive dwarf globular transition objects (DGTOs) or ultra compact dwarfs (UCDs) and to nuclei of nucleated dE galaxies. The average M/LV is 3±1, larger than the average M/LV of globular clusters in the Local Group galaxies. The correlations of structural parameters, velocity dispersion, masses and M/LV for the bright globular clusters extend the properties established for the most massive Local Group clusters towards those characteristic of dwarf elliptical galaxy nuclei and DGTOs/UCDs. The detection of the mass-radius and the mass-M/LV relations for the globular clusters with masses greater than ~ 2 × 106M⊙ provides the link between “normal” old globular clusters, young massive clusters, and evolved massive objects.

scholarly journals The theory of young cluster disruption

2010 ◽  
Vol 6 (S270) ◽  
pp. 283-286
Author(s):  
Simon P. Goodwin
Keyword(s):  
Star Formation ◽  
Globular Clusters ◽  
Velocity Dispersion ◽  
Star Clusters ◽  
Initial Values ◽  
Gas Removal ◽  
Residual Gas ◽  
The Masses ◽  
Effects Of Feedback ◽  
Massive Clusters

AbstractMost stars seem to form in clusters, but the vast majority of these clusters do not seem to survive much beyond their embedded phase. The most favoured mechanism for the early destruction of star clusters is the effect of the removal of residual gas by feedback which dramatically changes the cluster potential. The effects of feedback depend on the ratio of the masses of stars and gas, and the velocity dispersion of the stars at the onset of gas removal. As gas removal is delayed by a few Myr from star formation these crucial parameters can change significantly from their initial values. In particular, in dynamically cool and clumpy clusters, the stars will collapse to a far denser state and if they decouple from the gas then gas removal may be far less destructive than previously thought. This might well help explain the survival of very massive clusters, such as globular clusters, without the need for extremely high star formation efficiencies or initial masses far greater than their current masses.

scholarly journals Mv−σ Relation: A Universal Law?

1996 ◽  
Vol 174 ◽  
pp. 345-346
Author(s):  
S.R. Zaggia
Keyword(s):  
Globular Clusters ◽  
Luminosity Function ◽  
Velocity Dispersion ◽  
Local Group ◽  
Structural Parameters ◽  
Intrinsic Nature ◽  
Total Luminosity ◽  
Growing Body ◽  
Formation And Evolution ◽  
Universal Law

Globular clusters (GC) of different galaxies are thought to be similar in their intrinsic nature, despite the very different environments in which they reside. This statement is mainly based on the luminosity function of GC that appear to be similar for galaxies structurally very different (Secker and Harris 1993). To support the above conclusion only few other GC parameters have been used: integrated colors and metallicity index (Harris 1991). Now, there is a growing body of GC velocity dispersions of other local group galaxies which can be used to perform a useful comparison. The tool for such a comparison is the correlation between GC total luminosity, Mv, and velocity dispersion, σ, found by Djorgovski (1991). This is one of the best non trivial correlation of GC structural parameters that can give important answers to the problems of the formation and evolution of GCs.

scholarly journals Twins born in different environments? Nuclei of two dSphs: isolated galaxy KKS3 and E269-66, a close neighbor of NGC5128

2015 ◽  
Vol 12 (S316) ◽  
pp. 349-350
Author(s):  
Margarita Sharina ◽  
Alexei Kniazev ◽  
Igor Karachentsev
Keyword(s):  
Globular Clusters ◽  
Massive Star ◽  
Stellar Population ◽  
Central Star ◽  
Close Neighbor ◽  
Dwarf Spheroidal Galaxies ◽  
Star Forming ◽  
Star Formation Histories ◽  
Massive Clusters ◽  
Centaurus A

AbstractWe present the results of age, metallicity and radial velocity determination for central massive globular clusters (GCs) in dwarf spheroidal galaxies: KKs3 and ESO269-66. KKS3 is a unique isolated galaxy. ESO269-66 is a close neighbor of the giant S0 Centaurus A. The results contribute to the knowledge about the origin of massive star clusters and their host dSphs. The structure and star formation histories of the two dwarf galaxies look rather similar. Both of them have experienced several star-forming events. The most recent ones occurred 1-2 Gyr ago, and most powerful bursts happened 12-14 Gyrs ago. Our analysis has shown that both GCs appear to be 1-2 Gyr younger and 0.1-0.3 dex more metal-rich than the most ancient metal-poor stars in the host dSphs. We examine signatures of multiple stellar population in the GCs using our data. Since central star-forming bursts were extended in time, the massive clusters might be considered as nuclei of the galaxies.

scholarly journals Young and old massive star clusters and their stellar populations - Theoretical challenges for the next decade

2015 ◽  
Vol 12 (S316) ◽  
pp. 1-8
Author(s):  
Corinne Charbonnel
Keyword(s):  
Globular Clusters ◽  
Massive Star ◽  
Local Group ◽  
Stellar Populations ◽  
Low Mass Stars ◽  
Open Questions ◽  
Low Mass ◽  
Near Future ◽  
Massive Clusters ◽  
Two Populations

AbstractSeveral models presented in the literature compete to explain the origin of multiple stellar populations in globular clusters (GC), but they all fail to reproduce the large variety of present-day characteristics of these systems. In parallel, independent clues on GC early evolution may be derived from observations of young massive clusters (YMC) in the Local Group. But are these two populations of clusters related? And can we reconcile the informations and data concerning GCs and YMCs? Here we summarize some open questions on the nucleosynthetic origin of multiple stellar populations in GCs, on the actual evolution and characteristics of GC low-mass stars, and on early gas expulsion from massive clusters. We propose theoretical paths to be explored in the near future.

scholarly journals Radial Velocities of Globular Clusters in the Giant Elliptical Galaxy NGC 1399

1998 ◽  
Vol 115 (1) ◽  
pp. 121-129 ◽  
Author(s):  
Dante Minniti ◽  
Markus Kissler-Patig ◽  
Paul Goudfrooij ◽  
Georges Meylan
Keyword(s):  
Globular Clusters ◽  
Elliptical Galaxy ◽  
Radial Velocities

scholarly journals The Newtonian and MOND dynamical models of NGC 5128: Investigation of the dark matter contribution

2016 ◽  
pp. 9-20 ◽  
Author(s):  
S. Samurovic
Keyword(s):  
Dark Matter ◽  
Globular Clusters ◽  
Velocity Dispersion ◽  
Good Description ◽  
Isotropic Case ◽  
Dark Halo ◽  
Dynamical Models ◽  
Anisotropic Case ◽  
Early Type Galaxy ◽  
Centaurus A

We study the well-known nearby early-type galaxy NGC 5128 (Centaurus A) and use the sample of its globular clusters to analyze its dynamics. We study both Newtonian and MOND models assuming three cases of orbital anisotropies: isotropic case, mildly tangentially anisotropic case and the radially anisotropic case based on the literature. We find that there are two regions with different values of the velocity dispersion: interior to ~ 3 effective radii the value of the velocity dispersion is approximately 150 km s?1 , whereas beyond ~ 3 effective radii its value increases to approximately 190 km s?1 , thus implying the increase of the total cumulative mass which is indicative of the existence of dark matter there in the Newtonian approach: the mass-to-light increases from M/LB = 7 in the inner regions to M/LB = 26 in the outer regions. We found that the Navarro-Frenk-White (NFW) model with dark halo provides good description of the dynamics of NGC 5128. Using three MOND models (standard, simple and toy), we find that they all provide good fits to the velocity dispersion of NGC 5128 and that no additional dark component is needed in MOND.

scholarly journals MOCCA Survey Database: Extra Galactic Globular Clusters. I. Method and first results

2021 ◽  
Author(s):  
A Leveque ◽  
M Giersz ◽  
M Paolillo
Keyword(s):  
Globular Clusters ◽  
Surface Brightness ◽  
Velocity Dispersion ◽  
Structural Parameters ◽  
Dynamical Evolution ◽  
Central Surface ◽  
First Results ◽  
Preliminary Study ◽  
Galactic Globular Clusters ◽  
Gaia Dr2

Abstract Over the last few decades, exhaustive surveys of extra Galactic globular clusters (EGGCs) have become feasible. Only recently, limited kinematical information of globular clusters (GCs) were available through Gaia DR2 spectroscopy and also proper motions. On the other hand, simulations of GCs can provide detailed information about the dynamical evolution of the system. We present a preliminary study of EGGCs- properties for different dynamical evolutionary stages. We apply this study to 12 Gyr-old GCs simulated as part of the MOCCA Survey Database. Mimicking observational limits, we consider only a subssample of the models in the database, showing that it is possible to represent observed Milky Way GCs. In order to distinguish between different dynamical states of EGGCs, at least three structural parameters are necessary. The best distinction is achieved by considering the central parameters, those being observational core radius, central surface brightness, ratio between central and half-mass velocity dispersion, or similarly considering the central color, the central V magnitude and the ratio between central and half-mass radius velocity dispersion, although such properties could be prohibitive with current technologies. A similar but less solid result is obtained considering the average properties at the half-light radius, perhaps accessible presently in the Local Group. Additionally, we mention that the color spread in EGGCs due to internal dynamical models, at fixed metallcity, could be just as important due to the spread in metallicity.

scholarly journals Astrometric Distances of Globular Clusters

1988 ◽  
Vol 126 ◽  
pp. 523-524
Author(s):  
Kyle Cudworth ◽  
Ruth C. Peterson
Keyword(s):  
Radial Velocity ◽  
High Precision ◽  
Proper Motion ◽  
Globular Clusters ◽  
Small Distance ◽  
Radial Velocities ◽  
Proper Motions ◽  
Velocity Dispersions

With high-precision radial velocities and proper motions, one can equate the proper motion and radial velocity dispersions to obtain astrometric distances independent of any standard candles. We discuss the method and the small distance it yields to M 22.

scholarly journals The relation between velocity dispersions and chemical abundances in RAVE giants

2017 ◽  
Vol 12 (S330) ◽  
pp. 259-260
Author(s):  
Rodolfo Smiljanic ◽  
Rafael Silva de Souza
Keyword(s):  
Stellar Population ◽  
Velocity Dispersion ◽  
Bayesian Framework ◽  
Radial Velocities ◽  
Proper Motions ◽  
Chemical Abundances ◽  
Gaia Dr1 ◽  
Velocity Dispersions ◽  
Kinematic Properties ◽  
Robust Result

AbstractWe developed a Bayesian framework to determine in a robust way the relation between velocity dispersions and chemical abundances in a sample of stars. Our modelling takes into account the uncertainties in the chemical and kinematic properties. We make use of RAVE DR5 radial velocities and abundances together with Gaia DR1 proper motions and parallaxes (when possible, otherwise UCAC4 data is used). We found that, in general, the velocity dispersions increase with decreasing [Fe/H] and increasing [Mg/Fe]. A possible decrease in velocity dispersion for stars with high [Mg/Fe] is a property of a negligible fraction of stars and hardly a robust result. At low [Fe/H] and high [Mg/Fe] the sample is incomplete, affected by biases, and likely not representative of the underlying stellar population.

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