scholarly journals Stellar Populations in Star Clusters: The Role Played by Stochastic Effects

2002 ◽  
Vol 207 ◽  
pp. 616-624 ◽  
Author(s):  
Gustavo Bruzual A.
Keyword(s):  
Stellar Evolution ◽  
Ad Hoc ◽  
Star Clusters ◽  
Stellar Populations ◽  
Evolution Theory ◽  
Agb Stars ◽  
Population Synthesis ◽  
Stochastic Effects

In this paper I combine the results of a set of population synthesis models with simple Montecarlo simulations of stochastic effects in the number of stars occupying sparsely populated stellar evolutionary phases, to show that the scatter observed in the magnitudes and colors of LMC and NGC 7252 star clusters can be understood in the framework of current stellar evolution theory, without the need to introduce ad-hoc corrections (e.g. artificially increasing the number of AGB stars).

scholarly journals Supernova searches and rates

2013 ◽  
Vol 9 (S296) ◽  
pp. 37-44
Author(s):  
Enrico Cappellaro
Keyword(s):  
Stellar Evolution ◽  
Rapid Development ◽  
Cosmic Time ◽  
Stellar Populations ◽  
Evolution Theory ◽  
Direct Link ◽  
Local Universe ◽  
Crucial Test

AbstractSupernova statistics, establishing a direct link between stellar populations and explosion scenarios, is a crucial test of stellar evolution theory. Nowadays, a number of SN searches in the local Universe and at high redshifts are allowing observational probes of long standing theoretical scenarios. I will briefly review some of the most interesting results in particular for what concern the evolution with cosmic time of the SN rate, which is one of the topic that in the last few years had a most rapid development.

scholarly journals TP-AGB stars in population synthesis models

2009 ◽  
Vol 5 (S262) ◽  
pp. 36-43 ◽  
Author(s):  
Paola Marigo ◽  
Léo Girardi ◽  
Alessandro Bressan ◽  
Bernhard Aringer ◽  
Marco Gullieuszik ◽  
...  
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
Magellanic Clouds ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Population Synthesis ◽  
Future Developments ◽  
First Results ◽  
Nearby Galaxies ◽  
The Subject

AbstractIn spite of its relevance, the Thermally Pulsing Asymptotic Giant Branch (TP-AGB) phase is one of the most uncertain phases of stellar evolution, and a major source of disagreement between the results of different population synthesis models of galaxies. I will briefly review the existing literature on the subject, and recall the basic prescriptions that have been used to fix the contribution of TP-AGB stars to the integrated light of stellar populations. The simplicity of these prescriptions greatly contrasts with the richness of details provided by present-day databases of AGB stars in the Magellanic Clouds, which are now being extended to other nearby galaxies. I will present the first results of an ongoing study aimed at simulating photometry, chemistry, pulsation, mass loss, dust properties of AGB star populations in resolved and un-resolved galaxies. We test our predictions against observations from various surveys of the Magellanic Clouds (DENIS, 2MASS, OGLE, MACHO, Spitzer, and AKARI). I will discuss the implications and outline the plan of future developments.

scholarly journals An Essay on Stellar Oscillations and Evolution

1983 ◽  
Vol 66 ◽  
pp. 457-467
Author(s):  
Icko Iben
Keyword(s):  
Stellar Evolution ◽  
Evolution Theory ◽  
Agb Stars ◽  
Solar Oscillation ◽  
High Luminosity ◽  
Stellar Oscillations ◽  
Classical Cepheids ◽  
Neutrino Fluxes ◽  
Oscillation Characteristics

AbstractIt is cautioned that solar models adjusted in such a way as to achieve a match between theoretical solar oscillation characteristics and observed ones may produce neutrino fluxes inconsistent with the observations and that this is likely to be explicable as a deficiency in modeling that portion of the envelope which is most strongly affected by uncertainties in the treatment of convection. Then follows a summary of how the results of pulsation theory and of stellar evolution theory have been used together to learn about the structure and evolution of RRLyrae stars, classical Cepheids, and high luminosity AGB stars.

scholarly journals Magellanic globulars as cosmological tools

1991 ◽  
Vol 148 ◽  
pp. 165-169
Author(s):  
Alvio Renzini
Keyword(s):  
Galaxy Formation ◽  
Stellar Evolution ◽  
Globular Clusters ◽  
Star Clusters ◽  
Dynamical Evolution ◽  
Mass Range ◽  
Magellanic Clouds ◽  
Evolution Theory ◽  
Mass Functions ◽  
The Ideal

The globular clusters (GC) of the Magellanic Clouds play a very important role for many astrophysical and cosmological topics. For example, they represent the ideal testground for stellar evolution theory, they allow us to study the the early dynamical evolution of star clusters, to obtain accurate initial mass functions in a fairly extended mass range, to calibrate the Cepheid period-luminosity relation, and so on. In this brief paper I will touch upon two items which are of considerable cosmological interest, and about which Magellanic Cloud globulars provide unique information. These topics concern i) GC formation in galaxies, and ii) the epoch of galaxy formation.

scholarly journals Star clusters and single stellar populations

2009 ◽  
Vol 5 (S266) ◽  
pp. 304-311
Author(s):  
Licai Deng ◽  
Yu Xin
Keyword(s):  
Stellar Evolution ◽  
Spectral Properties ◽  
Star Clusters ◽  
Stellar Populations ◽  
Current Theory ◽  
Binary Interaction ◽  
Interaction Theory ◽  
Blue Stragglers ◽  
Evolutionary Scenario

AbstractStar clusters are ideal laboratories to test the theory of stellar evolution and provide very tight constraints on the concept of single stellar poputions (SSPs). Observations show that some stars fail to conform to the theoretical evolutionary scenario applicable to single stars. These special objects, particularly blue stragglers, present a challenge to our current theory of stellar evolution. They may be very important in the context of the integrated spectral properties of clusters. Here, we review the construction of SSP models, both empirically using star clusters and theoretically based on binary-interaction theory.

scholarly journals Blue stragglers in star clusters and the conventional SSP models

2009 ◽  
Vol 5 (S266) ◽  
pp. 556-556
Author(s):  
Yu Xin ◽  
Richard de Grijs ◽  
Licai Deng ◽  
Pavel Kroupa
Keyword(s):  
Stellar Evolution ◽  
Stellar Population ◽  
Broad Band ◽  
Star Clusters ◽  
Open Clusters ◽  
Formation Mechanisms ◽  
Evolution Theory ◽  
Blue Stragglers ◽  
Blue Straggler ◽  
Conventional Picture

AbstractThe presence of blue straggler stars (BSs) as secure members of star clusters poses a major challenge to the conventional picture of simple stellar population (SSP) models. The models are based on the stellar evolution theory of single stars, while the major formation mechanisms of BSs are all correlated with stellar interactions. Based on a sufficient working sample including 100 Galactic open clusters, one Galactic globular cluster, and seven Magellanic Cloud star clusters, we discuss the modifications of the properties of broad-band colors and Lick indices of the standard SSP models due to BS populations.

scholarly journals Star clusters as laboratories for stellar and dynamical evolution

2010 ◽  
Vol 368 (1913) ◽  
pp. 755-782 ◽  
Author(s):  
Jason S. Kalirai ◽  
Harvey B. Richer
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
First Generation ◽  
Main Sequence ◽  
Star Clusters ◽  
Dynamical Evolution ◽  
Stellar Populations ◽  
Stellar Mass ◽  
Theoretical Studies ◽  
Chemical Enrichment

Open and globular star clusters have served as benchmarks for the study of stellar evolution owing to their supposed nature as simple stellar populations of the same age and metallicity. After a brief review of some of the pioneering work that established the importance of imaging stars in these systems, we focus on several recent studies that have challenged our fundamental picture of star clusters. These new studies indicate that star clusters can very well harbour multiple stellar populations, possibly formed through self-enrichment processes from the first-generation stars that evolved through post-main-sequence evolutionary phases. Correctly interpreting stellar evolution in such systems is tied to our understanding of both chemical-enrichment mechanisms, including stellar mass loss along the giant branches, and the dynamical state of the cluster. We illustrate recent imaging, spectroscopic and theoretical studies that have begun to shed new light on the evolutionary processes that occur within star clusters.

scholarly journals Are planetary nebulae derived from multiple evolutionary scenarios?

2011 ◽  
Vol 7 (S283) ◽  
pp. 192-195 ◽  
Author(s):  
David J. Frew ◽  
Quentin A. Parker
Keyword(s):  
Stellar Evolution ◽  
Planetary Nebulae ◽  
Evolution Theory ◽  
Population Synthesis ◽  
Evolutionary Pathways ◽  
Central Stars

AbstractOur understanding of planetary nebulae has been significantly enhanced as a result of several recent large surveys (Parker et al., these proceedings). These new discoveries suggest that the ‘PN phenomenon’ is in fact more heterogeneous than previously envisaged. Even after the careful elimination of mimics from Galactic PN catalogues, there remains a surprising diversity in the population of PNe and especially their central stars. Indeed, several evolutionary scenarios are implicated in the formation of objects presently catalogued as PNe. We provide a summary of these evolutionary pathways and give examples of each. Eventually, a full census of local PNe can be used to confront both stellar evolution theory and population synthesis models.

scholarly journals Star clusters as simple stellar populations

2010 ◽  
Vol 368 (1913) ◽  
pp. 783-799 ◽  
Author(s):  
Gustavo Bruzual A.
Keyword(s):  
Star Clusters ◽  
Stellar Populations ◽  
Mass Function ◽  
Initial Mass Function ◽  
Population Synthesis ◽  
Stochastic Fluctuations ◽  
Composite Models ◽  
Stellar Initial Mass Function ◽  
Absolute Magnitudes ◽  
Star Formation Histories

In this paper, I review to what extent we can understand the photometric properties of star clusters, and of low-mass, unresolved galaxies, in terms of population-synthesis models designed to describe ‘simple stellar populations’ (SSPs), i.e. groups of stars born at the same time, in the same volume of space and from a gas cloud of homogeneous chemical composition. The photometric properties predicted by these models do not readily match the observations of most star clusters, unless we properly take into account the expected variation in the number of stars occupying sparsely populated evolutionary stages, owing to stochastic fluctuations in the stellar initial mass function. In this case, population-synthesis models reproduce remarkably well the full ranges of observed integrated colours and absolute magnitudes of star clusters of various ages and metallicities. The disagreement between the model predictions and observations of cluster colours and magnitudes may indicate problems with or deficiencies in the modelling, and does not necessarily tell us that star clusters do not behave like SSPs. Matching the photometric properties of star clusters using SSP models is a necessary (but not sufficient) condition for clusters to be considered SSPs. Composite models, characterized by complex star-formation histories, also match the observed cluster colours.

scholarly journals Comparing six evolutionary population synthesis models

2009 ◽  
Vol 5 (S262) ◽  
pp. 372-373
Author(s):  
Y. C. Liang ◽  
X. Y. Chen ◽  
F. Hammer ◽  
M. Rodrigues ◽  
Y. H. Zhao ◽  
...  
Keyword(s):  
Stellar Evolution ◽  
Stellar Populations ◽  
Population Synthesis ◽  
Star Forming ◽  
The Individual

AbstractWe compare six evolutionary population synthesis (EPS) models, which have been popularly used in stellar populations analyses for galaxies. The resulted stellar populations of star-forming galaxies and E+A galaxies from these EPS models show that the dominated contribution (fraction) from young, intermediate and old populations to their lights are consistent, although the individual numbers may change significantly, 3-30%, which could relate to the different ingredients in EPS models, such as the stellar library, the stellar evolution tracks etc.

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