scholarly journals The ACS Survey of Galactic Globular Clusters. II. Stellar Evolution Tracks, Isochrones, Luminosity Functions, and Synthetic Horizontal-Branch Models

2007 ◽  
Vol 134 (1) ◽  
pp. 376-390 ◽  
Author(s):  
Aaron Dotter ◽  
Brian Chaboyer ◽  
Darko Jevremović ◽  
E. Baron ◽  
Jason W. Ferguson ◽  
...  
Keyword(s):  
Stellar Evolution ◽  
Globular Clusters ◽  
Horizontal Branch ◽  
Luminosity Functions ◽  
Galactic Globular Clusters

scholarly journals Horizontal branch morphology: A new photometric parametrization

2019 ◽  
Vol 629 ◽  
pp. A53 ◽  
Author(s):  
M. Torelli ◽  
G. Iannicola ◽  
P. B. Stetson ◽  
I. Ferraro ◽  
G. Bono ◽  
...  
Keyword(s):  
Metal Content ◽  
Globular Clusters ◽  
Linear Trend ◽  
Cumulative Number ◽  
Horizontal Branch ◽  
Imaging Data ◽  
Galactic Globular Clusters ◽  
Absolute Age ◽  
Advanced Camera For Surveys ◽  
Branch Morphology

Context. Theory and observations indicate that the distribution of stars along the horizontal branch of Galactic globular clusters mainly depends on the metal content. However, the existence of globular clusters with similar metal content and absolute age but different horizontal branch morphologies, suggests the presence of another parameter affecting the star distribution along the branch. Aims. To investigate the variation of the horizontal branch morphology in Galactic globular clusters, we define a new photometric horizontal branch morphology index, overcoming some of the limitations and degeneracies affecting similar indices available in the literature. Methods. We took advantage of a sample of 64 Galactic globular clusters, with both space-based imaging data (Advanced Camera for Surveys survey of Galactic globular clusters) and homogeneous ground-based photometric catalogues in five different bands (U, B, V, R, I). The new index, τHB, is defined as the ratio between the areas subtended by the cumulative number distribution in magnitude (I) and in colour (V − I) of all stars along the horizontal branch. Results. This new index shows a linear trend over the entire range in metallicity (−2.35 ≤ [Fe/H] ≤ −0.12) covered by our Galactic globular cluster sample. We found a linear relation between τHB and absolute cluster ages. We also found a quadratic anti-correlation with [Fe/H], becoming linear when we eliminate the age effect on τHB values. Moreover, we identified a subsample of eight clusters that are peculiar according to their τHB values. These clusters have bluer horizontal branch morphology when compared to typical ones of similar metallicity. These findings allow us to define them as the ’second parameter’ clusters in the sample. A comparison with synthetic horizontal branch models suggests that they cannot be entirely explained with a spread in helium content.

On the Two Oosterhoff Groups of Globular Clusters

1973 ◽  
Vol 21 ◽  
pp. 196-196
Author(s):  
T. S. Van Albada ◽  
Norman Baker
Keyword(s):  
Stellar Evolution ◽  
Globular Clusters ◽  
Transition Point ◽  
Transition Period ◽  
Observational Evidence ◽  
Horizontal Branch ◽  
Average Difference ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Lyrae Stars

AbstractThe observational evidence leading to the classification, following Oosterhoff, of globular clusters containing RR Lyrae stars into two distinct groups, is summarized and discussed in the light of results of stellar evolution theory and pulsation theory. The dichotomy is caused, at least in part, by a dichotomy in the ‘transition period’ between the type-ab and type-c stars which reflects a difference in effective temperature at the transition point. When this difference is accounted for, there remains a smaller average difference between the groups, though no longer a clear dichotomy, that is probably a mass and luminosity effect. If this remaining difference is interpreted as a luminosity effect the average difference in luminosity between the two Oosterhoff groups is at most 0.1 mag. It is suggested that Christy’s theoretical relationship between transition period and luminosity cannot be valid, at least not for clusters of different Oosterhoff groups. It is conjectured that the transition-temperature dichotomy may be a reflection of different predominant directions of evolution along the horizontal branch, accompanied by a hysteresis effect in the pulsations.

scholarly journals TheHubble Space TelescopeUV Legacy Survey of Galactic globular clusters – XI. The horizontal branch in NGC 6388 and NGC 6441

2016 ◽  
Vol 465 (1) ◽  
pp. 1046-1056 ◽  
Author(s):  
M. Tailo ◽  
F. D'Antona ◽  
A. P. Milone ◽  
A. Bellini ◽  
P. Ventura ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Horizontal Branch ◽  
Galactic Globular Clusters

scholarly journals Core collapse and horizontal-branch morphology in Galactic globular clusters

2013 ◽  
Vol 554 ◽  
pp. A129 ◽  
Author(s):  
M. Pasquato ◽  
G. Raimondo ◽  
E. Brocato ◽  
C. Chung ◽  
A. Moraghan ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Core Collapse ◽  
Horizontal Branch ◽  
Galactic Globular Clusters ◽  
Branch Morphology

scholarly journals The peculiar horizontal branch morphology of the Galactic globular clusters NGC 6388 and NGC 6441: new insights from UV observations

2007 ◽  
Vol 474 (1) ◽  
pp. 105-119 ◽  
Author(s):  
G. Busso ◽  
S. Cassisi ◽  
G. Piotto ◽  
M. Castellani ◽  
M. Romaniello ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Horizontal Branch ◽  
Galactic Globular Clusters ◽  
Branch Morphology

scholarly journals WFPC2 UV survey of Galactic globular clusters. The Horizontal Branch temperature distribution

2014 ◽  
Vol 355 (1) ◽  
pp. 117-122 ◽  
Author(s):  
E. P. Lagioia ◽  
E. Dalessandro ◽  
F. R. Ferraro ◽  
B. Lanzoni ◽  
M. Salaris
Keyword(s):  
Temperature Distribution ◽  
Globular Clusters ◽  
Horizontal Branch ◽  
Galactic Globular Clusters

scholarly journals Structure Parameters of Galactic Globular Clusters

1985 ◽  
Vol 113 ◽  
pp. 541-577 ◽  
Author(s):  
R. F. Webbink
Keyword(s):  
Globular Clusters ◽  
Mass Density ◽  
Structure Parameters ◽  
Horizontal Branch ◽  
Galactocentric Distance ◽  
Central Mass ◽  
Central Surface ◽  
The Galaxy ◽  
Relaxation Time Scale ◽  
Galactic Globular Clusters

Observed and derived structure parameters are tabulated for 154 galactic globular clusters, 7 dwarf spheroidal satellites of the Galaxy, and 6 globular clusters in the Fornax dwarf spheroidal. Observational parameters listed include equatorial coordinates, apparent level of the horizontal branch, reddening, subgiant branch color at the horizontal branch level, limiting and core angular radii, integrated magnitudes, and central surface brightnesses. Derived parameters include galactic coordinates, heliocentric and galactocentric distance, metallicity, limiting and core radii, central relaxation time scale, central mass density, central velocity dispersion, and central escape velocity.

scholarly journals The Evolution of the Integrated Colors of Globular Clusters and Elliptical Galaxies

1978 ◽  
Vol 80 ◽  
pp. 345-348 ◽  
Author(s):  
R.B. Ciardullo ◽  
P. Demarque
Keyword(s):  
Stellar Evolution ◽  
Globular Clusters ◽  
Theoretical Data ◽  
Mass Function ◽  
Elliptical Galaxies ◽  
Initial Mass Function ◽  
Stellar Atmospheres ◽  
Color Evolution ◽  
Luminosity Functions ◽  
First Results

The purpose of this paper is to show the first results of a program designed to construct population models of stellar systems on the basis of theoretical data of stellar evolution. Synthetic HR diagrams were obtained using the isochrones and luminosity functions of Ciardullo and Demarque (1977). This last work is based on the stellar models of the Yale - IBM research group (Mengel, Sweigart, Demarque and Gross 1978; Sweigart and Gross 1976; 1978). The conversion from the theoretical HR diagram to observable parameters is made with the help of theoretical model stellar atmospheres principally due to Kurucz (1976), Relyea (1976) and Bell and Gustafsson (1975). The program provides a synthetic C-M diagram and integrated properties for the system given the following parameters: the chemical composition in terms of the (Y,Z) pair, the age, the total number of stars, the initial mass function (IMF) and the law of mass loss from stars in the system. In this brief paper, we shall concentrate on theintegratedproperties of theoretical star clusters and then remark on some interesting consequences for the color evolution of elliptical galaxies.

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