scholarly journals Empirical estimates of the Na–O anti-correlation in 95 Galactic globular clusters

2019 ◽  
Vol 624 ◽  
pp. A24 ◽  
Author(s):  
Eugenio Carretta
Keyword(s):  
Globular Clusters ◽  
Structural Parameters ◽  
Stellar Populations ◽  
Red Giants ◽  
Light Elements ◽  
Empirical Estimates ◽  
Bivariate Correlation ◽  
Identity Line ◽  
Consistent Picture ◽  
Galactic Globular Clusters

Large star-to-star abundance variations are direct evidence of multiple stellar populations in Galactic globular clusters (GCs). The main and most widespread chemical signature is the anti-correlation of the stellar Na and O abundances. The interquartile range (IQR) of the [O/Na] ratio is well suited to quantifying the extent of the anti-correlation and to probe its links to global cluster parameters. However, since it is quite time consuming to obtain precise abundances from spectroscopy for large samples of stars in GCs, here we show empirical calibrations of IQR[O/Na] based on the O, Na abundances homogeneously derived from more than 2000 red giants in 22 GCs in our FLAMES survey. We find a statistically robust bivariate correlation of IQR as a function of the total luminosity (a proxy for mass) and cluster concentration c. Calibrated and observed values lie along the identity line when a term accounting for the horizontal branch (HB) morphology is added to the calibration, from which we obtained empirical values for 95 GCs. Spreads in proton-capture elements O and Na are found for all GCs in the luminosity range from MV = −3.76 to MV = −9.98. This calibration reproduces in a self-consistent picture the link of abundance variations in light elements with the He enhancements and its effect on the stellar distribution on the HB. We show that the spreads in light elements seem already to be dependent on the initial GC masses. The dependence of IQR on structural parameters stems from the well known correlation between c and MV, which is likely to be of primordial origin. Empirical estimates can be used to extend our investigation of multiple stellar populations to GCs in external galaxies, up to M 31, where even integrated light spectroscopy may currently provide only a hint of such a phenomenon.

scholarly journals Bayesian analysis of two stellar populations in Galactic globular clusters– III. Analysis of 30 clusters

2016 ◽  
Vol 463 (4) ◽  
pp. 3768-3782 ◽  
Author(s):  
R. Wagner-Kaiser ◽  
D. C. Stenning ◽  
A. Sarajedini ◽  
T. von Hippel ◽  
D. A. van Dyk ◽  
...  
Keyword(s):  
Bayesian Analysis ◽  
Globular Clusters ◽  
Stellar Populations ◽  
Galactic Globular Clusters

scholarly journals BAYESIAN ANALYSIS OF TWO STELLAR POPULATIONS IN GALACTIC GLOBULAR CLUSTERS. II. NGC 5024, NGC 5272, AND NGC 6352

2016 ◽  
Vol 826 (1) ◽  
pp. 42 ◽  
Author(s):  
R. Wagner-Kaiser ◽  
D. C. Stenning ◽  
E. Robinson ◽  
T. von Hippel ◽  
A. Sarajedini ◽  
...  
Keyword(s):  
Bayesian Analysis ◽  
Globular Clusters ◽  
Stellar Populations ◽  
Galactic Globular Clusters

scholarly journals Hubble Space Telescope Studies of the Dense Central Regions of Globular Clusters

1996 ◽  
Vol 174 ◽  
pp. 19-28
Author(s):  
Puragra Guhathakurta ◽  
Brian Yanny ◽  
Donald P. Schneider ◽  
John N. Bahcall
Keyword(s):  
Density Profile ◽  
Globular Clusters ◽  
Hubble Space Telescope ◽  
Stellar Populations ◽  
Core Collapse ◽  
Red Giants ◽  
Space Telescope ◽  
Blue Straggler ◽  
Central Regions ◽  
Stellar Density

We present results from an ongoing program to probe the dense central parts of Galactic globular clusters using multicolor Hubble Space Telescope images (WF/PC-I and WFPC2). Our sample includes the dense clusters M15, 47 Tuc, M30, NGC 6624, M3 and M13. The two main goals of our program are to measure the shape of stellar density profile in clusters (the slope of the density cusp in post core collapse clusters, in particular) and to understand the nature of evolved stellar populations in very dense regions and their variation as a function of radius. The latter includes studies of blue straggler stars and of the central depletion of bright red giants. Our recent WFPC2 study of M15 is described in detail.

scholarly journals G2C2 – III. Structural parameters for Galactic globular clusters in SDSS passbands

2015 ◽  
Vol 450 (3) ◽  
pp. 2692-2707 ◽  
Author(s):  
Joachim Vanderbeke ◽  
Roberto De Propris ◽  
Sven De Rijcke ◽  
Maarten Baes ◽  
Michael J. West ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Structural Parameters ◽  
Galactic Globular Clusters

Internal kinematics of multiple stellar populations in globular clusters

2019 ◽  
Vol 14 (S351) ◽  
pp. 324-328
Author(s):  
Mattia Libralato
Keyword(s):  
High Precision ◽  
Globular Clusters ◽  
Hubble Space Telescope ◽  
Stellar Populations ◽  
Stellar Systems ◽  
Proper Motions ◽  
Space Telescope ◽  
Formation And Evolution ◽  
Galactic Globular Clusters ◽  
Shed Light

AbstractSpectroscopy and photometry have revealed existence, complexity and properties of the multiple stellar populations (mPOPs) hosted in Galactic globular clusters. However, the conundrum of the formation and evolution of mPOPs is far from being completely exploited: the available pieces of information seem not enough to shed light on these topics. Astrometry, and in particular high-precision proper motions, can provide us the sought-after answers about how mPOPs formed and have evolved in these ancient stellar systems. In the following, I present a brief overview of the observational results on the internal kinematics of the mPOPs in some GCs thanks to Hubble Space Telescope high-precision proper motions.

scholarly journals Helium-rich stars in globular clusters: constraints for self-enrichment by massive stars

2009 ◽  
Vol 5 (S268) ◽  
pp. 135-140 ◽  
Author(s):  
Thibaut Decressin ◽  
G. Meynet ◽  
C. Charbonnel
Keyword(s):  
Globular Clusters ◽  
Massive Stars ◽  
Stellar Populations ◽  
The Self ◽  
Heavy Elements ◽  
Light Elements ◽  
Intracluster Gas ◽  
Fast Rotating

AbstractGlobular clusters exhibit peculiar chemical patterns where Fe and heavy elements are constant inside a given cluster while light elements (Li to Al) show strong star-to-star variations. This pattern can be explained by self-pollution of the intracluster gas by the slow winds of fast rotating massive stars. Besides, several main sequences have been observed in several globular clusters which can be understood only with different stellar populations with distinct He content. Here we explore how these He abundances can constrain the self-enrichment in globular clusters.

Multiple Stellar Populations: the evolutionary framework

2012 ◽  
Vol 10 (H16) ◽  
pp. 245-246
Author(s):  
Santi Cassisi
Keyword(s):  
Globular Clusters ◽  
Stellar Populations ◽  
Stellar Model ◽  
Photometric Data ◽  
Stellar Systems ◽  
Huge Amount ◽  
Stellar Models ◽  
Galactic Globular Clusters ◽  
New Generation

AbstractIn these last years a huge amount of both spectroscopical and photometric data has provided a plain evidence of the fact that Galactic globular clusters (GCs) host various stellar sub-populations characterized by peculiar chemical patterns. The need of properly interpreting the various observational features observed in the Color-Magnitude Diagrams (CMDs) of these stellar systems requires a new generation of stellar models properly accounting for these chemical peculiarities both in the stellar model computations and in the color - Teff transformations. In this review we discuss the evolutionary framework that is mandatory in order to trace the various sub-populations in any given GC.

HR Diagrams of Galaxies: Ages and Stages of Evolution

1978 ◽  
Vol 80 ◽  
pp. 247-257
Author(s):  
Beatrice M. Tinsley
Keyword(s):  
Globular Clusters ◽  
Milky Way ◽  
Stellar Populations ◽  
Young Star ◽  
Red Giants ◽  
Type I ◽  
Type Ii ◽  
Hubble Sequence ◽  
The Galaxy ◽  
Bright Blue

Baade (1944) based his concept of stellar populations in galaxies on the HR diagrams that he inferred from the magnitude at which their brightest stars could be resolved. His type I population had bright blue supergiants like those in the disk of the Milky Way, while the brightest stars in type II were the red giants found in globular clusters. He postulated that the Hubble sequence of galaxy types from irregulars to ellipticals contained increasing proportions of Population II relative to Population I, and that similar differences characterized nuclear bulges of spirals relative to their disks. A very important revision of this picture came with the discovery by Morgan and Mayall (1957; Morgan, 1956, 1959) that the integrated blue light of the nuclear bulges of M31 and the Galaxy is dominated by strong-lined CN giants, not by the weak-lined type found in globular clusters. On the basis of integrated spectra of galaxies, Morgan developed a revised population scheme, in which the extreme types are a young-star rich population, like Baade's extreme Population I, and a young-star deficient population, analogous to Population II but generally metal-rich. Different proportions of these two types are still thought to represent the main differences among stellar populations in different regions of galaxies.

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