Valentina Luridiana

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The probabilistic nature of the IMF in stellar systems implies that clusters of the same mass and age do not present the same unique values of their observed parameters. Instead they follow a distribution. We address the study of such distributions in terms of their confidence limits that can be obtained by evolutionary synthesis models. These confidence(More)
In this paper we develop a new formalism for the theoretical study of stellar populations, which provides simple mathematical tools to account for the distributed nature of stellar population properties. This formalism is as accurate as large Monte Carlo simulations and as simple as standard synthesis models, being at the same time more powerful than either(More)
Context. Synthesis models predict the integrated properties of stellar populations. Several problems exist in this field, mostly related to the fact that integrated properties are distributed. To date, this aspect has been either ignored (as in standard synthesis models, which are inherently deterministic) or interpreted phenomenologically (as in Monte(More)
We discuss the effects of collisional enhancement of Balmer lines on the determination of the primordial helium abundance. To this aim, we present a photoionization model of the metal-poor extragalactic H II region SBS 0335–052. We show that the derived helium abundance (Y ) of this H II region depends on the amount of collisional excitation affecting the(More)
The primordial abundance of He, YP , is one of the hottest themes in present-day astronomy, mostly due to its cosmological relevance. The disagreement between different determinations has been currently reduced to the 1-2% level, but these differences are still large enough to have deep implications for Big-Bang nucleosynthesis. It is therefore crucial to(More)
We quantify the energy radiated through all the collisional lines in a photoionized nebula in the presence of temperature fluctuations in the form of hot spots caused by an unknown heating process. The excess energy radiated in the lines as a result of the fluctuations is found to scale linearly with their mean-square amplitude t. We find that the combined(More)
The presently accepted “Theory of the Universe” was pioneered 60 years ago by Gamow, Alpher and Herman. As a consequence of the, later dubbed, Hot Big-Bang, matter was neutrons, and after some decay protons, and a history of successive captures built up the elements. It wasn’t until some 15 years later (with the discovery of the Cosmic Microwave Background(More)