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تسجيل مستخدم جديدExtragalactic Star Clusters in Merging Galaxies
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The study of cluster populations as tracer of galaxy evolution is now quite possible with 8 m class telescopes and modern instrumentation. The cluster population can be used as a good tracer of the star forming episodes undergone by the merging system. We present two young galaxies mergers NGC3256 and NGC4038, and the studies about the young cluster population on those system. We found that the clusters ages are agree with the mergers age and their metallicities are consistent with them being the progenitors of the old metal rich globulars in ellipticals.
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We present Gemini optical spectroscopy of 23 young star clusters in NGC3256. We find that the cluster ages range are from few Myr to ~150 Myr. All these clusters are relatively massive (2--40)x 10^{5} msun$ and appear to be of roughly 1.5 zo metallic
ity. The majority of the clusters in our sample follow the same rotation curve as the gas and hence were presumably formed in the molecular-gas disk. However, a western subsample of five clusters has velocities that deviate significantly from the gas rotation curve. These clusters may either belong to the second spiral galaxy of the merger or may have formed in tidal-tail gas falling back into the system. We discuss our observations in light of other known cluster populations in merging galaxies, and suggest that NGC 3256 is similar to Arp 220, and hence may become an Ultra-luminous Infrared Galaxy as the merger progresses and the star-formation rate increases. Some of the clusters which appeared as isolated in our ground-based images are clearly resolved into multiple sub-components in the HST-ACS images. The same effect has been observed in the Antennae galaxies, showing that clusters are often not formed in isolation, but instead tend to form in larger groups or cluster complexes.
We compute the evolution of the space-dependent mass distribution of galaxies in clusters due to binary aggregations by solving a space-dependent Smoluchowski equation. We derive the distribution of intergalactic distance for different ranges of mass
(and of corresponding magnitude). We compare the results with the observed distributions, and find that the different degrees of luminosity segregation observed in clusters are well accounted for by our merging model. In addition, the presence of luminosity segregation is related to dynamical effects which also show up in different but connected observables, such as galaxy velocity profiles decreasing toward the center and X-ray measured beta-parameters smaller than 1. We predict both luminosity segregation and the observables above (being a product of binary aggregations) to be inversely correlated with the core radius and with the galaxy velocity dispersion; we discuss how the whole set of predictions compares with up-to-date observations.
We present Gemini optical spectroscopy of three young star clusters in the western tidal tail of NGC3256. Compact star clusters (as opposed to dwarf-galaxy candidates) in tidal tails are rare, with these three clusters the first for which detailed qu
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