<> "The repository administrator has not yet configured an RDF license."^^ . <> . . "An Optical Study of Young Stellar Clusters"^^ . "In the first part of this thesis a new analysis of the Orion Nebula Cluster, one of the most studied star-forming regions in the Galaxy, is presented. Based on multi-band optical photometry and spectroscopy obtained with the Wide-Field Imager (WFI) at the ESO/MPI 2.2-m telescope at La Silla Observatory, I study the systematic effects that bias the derivation of stellar parameters of pre-main sequence (PMS) stars. I derive the new H-R diagram of the entire region, and assign masses and ages to all the members. The age is found to be ∼ 2 − 3 Myr, older than previously estimated. I also confirm the presence of an age spread, and show how the previously found mass-age correlation can be affected by the sample incompleteness and uncertainties in the evolutionary models. In the second part of this thesis, I carry out a research on the low-mass stellar population of the young stellar cluster LH 95 in the Large Magellanic Cloud, based on deep optical photometry with the Advanced Camera for Surveys (ACS) onboard the Hubble Space Telescope; the deepest ever obtained toward this galaxy, down to V ≃ 28 mag. I isolate the PMS cluster population, and derive the first extragalactic Initial Mass Function (IMF) down to the subsolar regime. It shows a flattening below 1 M⊙, in agreement with the Galactic IMF once results are corrected for unresolved binarity. I study the age distribution of LH 95, introducing a statistical method to derive average age and age-spreads accounting simultaneously for unresolved binarity, differential extinction, variability, accretion and crowding of PMS stars. The best-fit solution for LH 95 suggests an age of ∼ 4 Myr with a gaussian age spread of σ ∼ 1.2 Myr. Finally, I study the early-type highmass stellar population of the cluster, through ground based spectroscopy obtained with the Fiber-fed Extended Range Optical Spectrograph (FEROS) at the ESO/MPI 2.2-m telescope at La Silla Observatory, and photometry from the 1-m telescope at Siding Spring Observatory. The derived stellar masses are combined with my results on the low-mass IMF of the cluster for the study of the most complete extragalactic IMF ever performed."^^ . "2010" . . . . . . . . "Nicola"^^ . "Da Rio"^^ . "Nicola Da Rio"^^ . . . . . . "An Optical Study of Young Stellar Clusters (PDF)"^^ . . . "Nicola_Da_Rio_PhD_thesis.pdf"^^ . . . "An Optical Study of Young Stellar Clusters (Other)"^^ . . . . . . "indexcodes.txt"^^ . . . "An Optical Study of Young Stellar Clusters (Other)"^^ . . . . . . "lightbox.jpg"^^ . . . "An Optical Study of Young Stellar Clusters (Other)"^^ . . . . . . "preview.jpg"^^ . . . "An Optical Study of Young Stellar Clusters (Other)"^^ . . . . . . "medium.jpg"^^ . . . "An Optical Study of Young Stellar Clusters (Other)"^^ . . . . . . "small.jpg"^^ . . "HTML Summary of #11437 \n\nAn Optical Study of Young Stellar Clusters\n\n" . "text/html" . . . "520 Astronomie"@de . "520 Astronomy and allied sciences"@en . .