We present an implementation of stellar evolution and chemical feedback for smoothed particle hydrodynamics simulations. We consider the timed release of individual elements by both massive (Type II supernovae and stellar winds) and intermediate-mass stars (Type Ia supernovae and asymptotic giant branch stars). We illustrate the results of our

Aims: We aim to derive the chemical behavior of a significant sample of PNe and HII regions in the irregular galaxy NGC 6822. The selected objects are distributed in different zones of the galaxy. Our purpose is to obtain the chemical abundances of the present interstellar medium (ISM), represented by H ii regions, and the corresponding values at

Desde el espacio exterior llegan constantemente a la Tierra gran cantidad de particulas cargadas, la mayoria protones, aunque algunas veces tambien llegan nucleos atomicos que pueden ser tan masivos como el hierro. El espectro de estas particulas abarca un rango muy amplio de energia y sigue una ley de potencias. Este espectro plantea el problema

Aims: One of the most striking features predicted by standard models of galaxy formation is the presence of anti-correlations in the matter distribution on large enough scales (r > r_c). Simple arguments show that the location of the length scale r_c, marking the transition from positive to negative correlations, is the same for any class of

We present a chemical abundance analysis based on high resolution UVES spectra of seventeen bright giant stars in the Globular Cluster (GC) M 22. We obtained an average iron abundance of [Fe/H] = -1.76±0.02 (internal errors only) and an α enhancement of 0.36±0.04 (internal errors only). Na and O, and Al and O follow the well known anticorrelations