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 Young Star Clusters in the LMC

1992 ◽  
Vol 45 (4) ◽  
pp. 407
Author(s):  
KC Freeman
Keyword(s):  
Mass Loss ◽  
Globular Clusters ◽  
Star Clusters ◽  
Dynamical Evolution ◽  
Mass Function ◽  
Young Star ◽  
Stellar Mass ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Young Star Clusters

The young globular star clusters in the LMC offer us insights into the formation and early dynamical evolution of globular clusters which are unobtainable from the old globular clusters in our Galaxy. Because these young clusters are so young and populous, they provide an opportunity to measure the upper end of the initial mass function by direct means and also through the dynamical effects of stellar mass loss on the structure of the clusters.

scholarly journals Dynamical Evolution of Mass-Segregated Clusters

2007 ◽  
Vol 3 (S246) ◽  
pp. 181-185
Author(s):  
Enrico Vesperini ◽  
Steve McMillan ◽  
Simon Portegies Zwart
Keyword(s):  
Mass Loss ◽  
Density Profile ◽  
Stellar Evolution ◽  
Star Clusters ◽  
Dynamical Evolution ◽  
Mass Function ◽  
Initial Mass Function ◽  
Initial Evolution ◽  
Stellar Initial Mass Function ◽  
Mass Segregation

AbstractWe present the results of a survey of N-body simulations aimed at exploring the implications of primordial mass segregation on the dynamical evolution of star clusters. We show that, in a mass-segregated cluster, the effect of early mass loss due to stellar evolution is, in general, more destructive than for an unsegregated cluster with the same density profile and leads to shorter lifetimes, a faster initial evolution toward less concentrated structure and flattening of the stellar initial mass function.

scholarly journals A Comparative Study of Globular Clusters

1996 ◽  
Vol 174 ◽  
pp. 1-7
Author(s):  
Daiichiro Sugimoto
Keyword(s):  
Stellar Evolution ◽  
Globular Clusters ◽  
Main Sequence ◽  
Star Clusters ◽  
Time History ◽  
Dynamical Evolution ◽  
The Core ◽  
The Standard Model ◽  
Mass Segregation ◽  
Stellar Density

This paper is intended for an introduction to the Symposium. In 47 Tuc many milli-second pulsars are found while none has been reported in ω Cen. One might think that in 47 Tuc they have been formed in the collapsed core through tidal capture of a main sequence star by a neutron star. If we use the standard model of gravothermal collapse of globular clusters to integrate the squared stellar density over the core and over its time history, we find, however, the accumulated probability of tidal capture is lower in 47 Tuc than ω Cen. Such contradiction suggests that it will be important to take account of mass segregation as well as stellar evolution in modelling dynamical evolution of star clusters.

scholarly journals On Some Peculiar Features in the Sequences of the Old Open Star Clusters

1974 ◽  
Vol 59 ◽  
pp. 109-111
Author(s):  
A. Maeder
Keyword(s):  
Chemical Composition ◽  
Stellar Evolution ◽  
Main Sequence ◽  
Star Clusters ◽  
Open Star Clusters ◽  
Hydrogen Burning ◽  
The Core ◽  
Open Star ◽  
Solar Type ◽  
Good Agreement

In spite of the rather good agreement between the theory of stellar evolution and the observations, there exist some difficulties when one compares closely the sequences of open star clusters and the theoretical isochrones. Several, if not all, of the old open star clusters seem to be concerned, especially those which are accurately measured, namely Praesepe, NGC 2360, 752, 3680 and M67. The problem concerns the gap occuring in the HR diagram at the end of the phase of hydrogen burning in the core; it corresponds to the phase of hydrogen exhaustion (or of overall contraction). The sequence of M67 has been studied by Racine (1971) and Torres-Peimbert (1971). The well apparent gap is located farther from the zero-age main sequence than indicated by the models and the hook towards a larger Teff predicted during this phase is not observed. Differences in chemical composition may not be held responsible for these anomalies. From Torres-Peimbert's models, it may be assumed that neither solar type, nor super metal rich composition are able to reduce the discrepancies. As a further illustration, let us mention the case of NGC 752. In Table I, the main features related to the gap are examined: the disagreement, like in M67, essentially concern features 1 and 2. The observations are based on a recent study of Grenon and Mermillod (1973) and on Bell's data (1972). Bell has also mentioned the existence of discrepancies. As in M67, the gap is too far from the zero-age main sequence and does not present any sudden turning towards a larger Teff.

scholarly journals A galaxy’s accretion history unveiled from its integrated spectrum

2019 ◽  
Author(s):  
Alina Boecker ◽  
Ryan Leaman ◽  
Glenn van de Ven ◽  
Mark A Norris ◽  
J Ted Mackereth ◽  
...  
Keyword(s):  
Stellar Populations ◽  
Mass Function ◽  
Stellar Mass ◽  
Ex Situ ◽  
Future Application ◽  
Chemical Enrichment ◽  
Spectral Fitting ◽  
Regularization Techniques ◽  
Galaxy Masses

Abstract We present a new method of quantifying a galaxy’s accretion history from its integrated spectrum alone. Using full spectral fitting and calibrated regularization techniques we show how we can accurately derive a galaxy’s mass distribution in age-metallicity space and further separate this into stellar populations from different chemical enrichment histories. By exploiting the fact that accreted lower mass galaxies will exhibit an offset to lower metallicities at fixed age compared to the in-situ stellar population, we quantify the fraction of light that comes from past merger events, that are long since mixed in phase-space and otherwise indistinguishable. Empirical age-metallicity relations (AMRs) parameterized for different galaxy masses are used to identify the accreted stellar populations and link them back to the progenitor galaxy’s stellar mass. This allows us to not only measure the host galaxy’s total ex-situ mass fraction (facc), but also quantify the relative amount of accreted material deposited by satellite galaxies of different masses, i.e. the accreted satellite mass function in analogy to the subhalo mass function. Using mock spectra of present-day, early-type galaxies with total stellar mass ∼109 − 1012 M⊙ from the EAGLE simulation suite we demonstrate that our method can recover the total accreted fraction to within $\approx 38 \%$, the stellar mass of the most massive accreted subhalo to within $\approx 56 \%$ and the slope of the accreted satellite mass function to within $\approx 17 \%$ of the true values from the EAGLE merger trees. Future application of this method to observations could potentially provide us accretion histories of hundreds of individual galaxies, for which deep integrated light spectroscopy is available.

scholarly journals Small and Intermediate Mass Stellar Evolution - Main Sequence and Close to It

1993 ◽  
Vol 137 ◽  
pp. 410-425 ◽  
Author(s):  
A. Noels ◽  
N. Grevesse
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
Turbulent Diffusion ◽  
Main Sequence ◽  
Main Sequence Stars ◽  
Intermediate Mass ◽  
Physical Mechanisms ◽  
Standard Models

AbstractWe present the standard models for small and intermediate main sequence stars and we discuss some of the problems arising with semiconvection and overshooting. The surface abundance of Li serves as a test for other physical mechanisms, including microscopic and turbulent diffusion, rotation and mass loss.

Globular clusters and their link with stellar populations in the Milky Way

2019 ◽  
Vol 14 (S351) ◽  
pp. 19-23
Author(s):  
David Yong
Keyword(s):  
Chemical Evolution ◽  
Globular Clusters ◽  
Milky Way ◽  
Star Clusters ◽  
Stellar Populations ◽  
Chemical Compositions ◽  
Chemical Abundance ◽  
Chemical Enrichment ◽  
Similarities And Differences ◽  
Insight Into

AbstractObservations of stellar chemical compositions enable us to identify connections between globular clusters and stellar populations in the Milky Way. In particular, chemical abundance ratios provide detailed insight into the chemical enrichment histories of star clusters and the field populations. For some elements, there are striking differences between field and cluster stars which reflect different nucleosynthetic processes and/or chemical evolution. The goal of this talk was to provide an overview of similarities and differences in chemical compositions between globular clusters and the Milky Way as well as highlighting a few areas for further examination.

scholarly journals IAU Focus Meeting 7: Stellar Physics in Galaxies throughout the Universe

2015 ◽  
Vol 11 (A29B) ◽  
pp. 139-141
Author(s):  
Claus Leitherer ◽  
Stéphane Charlot ◽  
Claudia Maraston
Keyword(s):  
Stellar Evolution ◽  
Binary Stars ◽  
Main Sequence ◽  
High Redshift ◽  
Mass Function ◽  
Initial Mass Function ◽  
General Assembly ◽  
Dust Production ◽  
Chemical Enrichment ◽  
The Universe

AbstractA 3-day Focus Meeting entitled “Stellar Physics in Galaxies throughout the Universe” was held during the IAU XXIX General Assembly. The meeting brought together astrophysicists from the stellar physics, extragalactic astrophysics and cosmology communities to discuss how current and future results can foster progress in these disjoint science areas. Areas covered include stellar evolution of single and binary stars from the zero-age main-sequence to the terminal stage, the feedback of stars to the interstellar medium via radiation, dust production and chemical enrichment, and the properties of the most massive stars and of cosmologically significant stellar phases such as AGB and Wolf-Rayet stars. The limitations of our understanding of the physics of local stars and their effects on, e.g., ages, chemical composition and the initial mass function of galaxies at low to high redshift were evaluated.

scholarly journals Stellar masers, circumstellar envelopes and supernova remnants

2007 ◽  
Vol 3 (S242) ◽  
pp. 236-245
Author(s):  
Athol J. Kemball
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
Supernova Remnants ◽  
Stellar Mass ◽  
Stellar Atmospheres ◽  
Late Type ◽  
Open Future ◽  
Circumstellar Envelopes ◽  
Recent Advances

AbstractThis paper reviews recent advances in the study or circumstellar masers and masers found toward supernova remnants. The review is organized by science focus area, including the astrophysics of extended stellar atmospheres, stellar mass-loss processes and outflows, late-type evolved stellar evolution, stellar maser excitation and chemistry, and the use of stellar masers as independent distance estimators. Masers toward supernova remnants are covered separately. Recent advances and open future questions in this field are explored.

scholarly journals The Effects of Main-Sequence Mass Loss on Surface C/N Abundance Ratios During the Ascent of the First Giant Branch

1989 ◽  
Vol 106 ◽  
pp. 228-228
Author(s):  
J. A. Guzik ◽  
T. E. Beach
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
Mass Fraction ◽  
Main Sequence ◽  
High Mass ◽  
Core Material ◽  
Main Sequence Stars ◽  
Rapid Rotation ◽  
Final Mass ◽  
Evolution Modeling

The surface C/N abundance ratios of many cluster and field G and K giants following the 1st dredge-up phase are much lower than predicted from standard stellar evolution modeling. The occurrence of substantial mass loss, either during or immediately after the main-sequence phase would both reduce the mass fraction of the unprocessed envelope necessary to contaminate with CN-cycle products, as well as allow CN-processing of a greater amount of core material during the earlier high-mass phase. Willson, Bowen and Struck-Marcell (1987) have proposed that a combination of pulsation and rapid rotation could drive substantial mass loss in main-sequence stars of initial mass 1-3 MΘ. We evolved a grid of 16 mass-losing models from the zero-age main sequence through 1st dredge-up. The models have initial masses of 1.25, 1.5, 1.75 and 2.0 MΘ, and exponentially decreasing mass-loss rates with e-folding times 0.2, 0.4, 1.0 and 2.0 Gyr; all models evolve toward a final mass of 1.0 M". Since the mass-loss epoch is short-lived, most of the models reach 1.0 M0 rapidly, and follow the evolutionary track of a standard 1 MΘ model redward away from the main sequence and up the 1st giant branch. The convecuve envelope deepens during 1st dredge-up to homogenize the outer 3/4 of the star's final mass.

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