Found 44 talks archived in The Galaxy

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Tuesday April 21, 2009
Dr. Santi Cassisi
INAF-Osservatorio Astronomico di Teramo, Italy

Abstract

The last few years have witnessed a growing amount of empirical evidence pointing to the existence of multiple stellar populations in some Galactic globular clusters. It is also becoming more and more clear that clusters, hosting multiple stellar populations, do share some common properties, but also differ from each other in various aspects. In this talk, I will review the recent results concerning the presence of multiple stellar populations in stellar clusters, emphasizing the (different) properties of the subpopulations in the various clusters, and how they have been interpreted so far. I will discuss also the global characteristics of "peculiar" clusters - hosting multiple populations - from different points of view, and compare them with "normal" clusters, to try and shed some light on their nature and origin.

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Monday October 27, 2008
Dr. Antonio Marín-Franch
Instituto de Astrofísica de Canarias, Spain

Abstract

Based on observations with the Advanced Camera for Surveys (ACS), I will present accurate relative ages for a sample of 64 Galactic globular clusters. This Hubble Space Telescope (HST) Treasury program has been designed to provide a new large, deep and homogeneous photometric database. Relative ages have been obtained using a main sequence fitting procedure between clusters in the sample. Relative ages are determined with an accuracy from 2% to 7%. It has been proved that derived ages are independent of the assumed theoretical models. The existence of two well defined Galactic globular cluster groups is found. A group of old globular clusters with an age dispersion of 6% and showing no age-metallicity relation, and, on the other hand, a younger group showing a clear age-metallicity relation similar to that found in the globular clusters associated to the Sagittarius dwarf galaxy. Roughly 1/3 of the clusters belong to the younger group. Considering these new results, it is very tempting to suggest a Milky Way's halo formation scenario in which two differentiated phases took place. A very fast collapse, where the old and coeval globular clusters where formed, followed by accretions of Milky Way's satellite galaxies.


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Friday July 11, 2008
Dr. Mauricio Tapia
Instituto de Astronomía, UNAM, Sede Ensenada, Mexico

Abstract

El jovencísimo cúmulo GM 24, a una distancia de 2 kpc, se encuentra embebido en una caliente nube de CO aislada, en donde se formó hace menos de 105 años. El núcleo del cúmulo se compone de estrellas O tardías y de tipo B principalmente y pareciera carecer actualmente de una población estelar de baja masa. Se presentan nuevas observaciones en el infrarrojo cercano y medio que dan mayor definición a las características de sus principales objetos estelares jóvenes.


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Thursday May 29, 2008
Dr. Antonio Sollima
Instituto de Astrofísica de Canarias, Spain

Abstract

I present the first results of a long term project devoted to the study of the evolution of the binary population in globular clusters. Using deep ACS@HST images of a sample of 13 globular clusters I estimated the fraction of binaries in the cores of these clusters. From a theoretical side, I developed a simplified analytical code which simulates the evolution of the properties of the binary population in a dynamically evolving globular cluster. The comparison between theory and observations allows to evaluate the efficiency of the various processes of binary formation and destruction in these stellar systems and their dependence on the main cluster structural and dynamical parameters.



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