The stellar population and the evolutionary state of HII regions and starburst galaxies

RHII and starbursts are both powered by massive stars. They are the main contributors to the heating of the ISM via radiative and mechanical energy. Techniques to derive the stellar content and the evolutionary state of RHIIs and starbursts from their ultraviolet and optical integrated light are reviewed. A prototypical RHII (NGC 604) and nuclear starburst (NGC 7714) are discussed in more detail. The results reveal the necessity of multiwavelength analyses of these objects to estimate their stellar content and their evolutionary state in a consistent way.Comment: Proceedings of the JENAM Conference (Toulouse, September 1999). To be published in New Astronomy Reviews, Editors Daniel Schaerer and Rosa Gonzalez Delgado. 12 pages, 7 figure

Electronic Raman scattering in quantum dots revisited

We present theoretical results concerning inelastic light (Raman) scattering from semiconductor quantum dots. The characteristics of each dot state (whether it is a collective or single-particle excitation, its multipolarity, and its spin) are determined independently of the Raman spectrum, in such a way that common beliefs used for level assignments in experimental spectra can be tested. We explore the usefulness of below band gap excitation and an external magnetic field to identify charge and spin excited states of a collective or single-particle nature.Comment: To appear in a special issue of Solid State Communications dedicated to Eli Burstei

A VLT study of metal-rich extragalactic H II regions. I. Observations and empirical abundances

We have obtained spectroscopic observations from 3600 Angstrom to 9200 Angstrom with FORS at the Very Large Telescope for approximately 70 H II regions located in the spiral galaxies NGC 1232, NGC 1365, NGC 2903, NGC 2997 and NGC 5236. These data are part of a project aiming at measuring the chemical abundances and characterizing the massive stellar content of metal-rich extragalactic H II regions. In this paper we describe our dataset, and present emission line fluxes for the whole sample. In 32 H II regions we measure at least one of the following auroral lines: [S II]4072, [N II]5755, [S III]6312 and [O II]7325. From these we derive electron temperatures, as well as oxygen, nitrogen and sulphur abundances, using classical empirical methods (both so-called "Te-based methods" and "strong line methods"). Under the assumption that the temperature gradient does not introduce severe biases, we find that the most metal-rich nebulae with detected auroral lines are found at 12+log(O/H)~8.9, i.e. about 60% larger than the adopted solar value. However, classical abundance determinations in metal-rich H II regions may be severely biased and must be tested with realistic photoionization models. The spectroscopic observations presented in this paper will serve as a homogeneous and high-quality database for such purpose.Comment: Accepted for publication in Astronomy and Astrophysic