Physical parameters and chemical abundances in bipolar PNe

The Physical Parameters and Excitation of Jets and Knots in PNe

We are carrying out a study of the physical parameters and excitation of low-ionization structures (LIS) in planetary nebulae (PNe). Since the optical morphology and kinematics of the LIS and the main components (rims, shells and haloes) of our sample were studied previously, our main goal now is to search for: i) the density contrasts between jets/knots and the main nebular components; ii) the...

Observing Chemical Abundances in Comets

The atomic resonance lines of the major elements have been observed in the atmospheres of a few comets, by using vacuum ultraviolet spectrographs on board rockets or orbiting observatories. Dust-to-gas ratios have also been deduced for two comets through a Finson-Probstein's analysis of their dust-tail isophotes. The geometric albedo of the dust for the phase angle a of the observations is not ...

Chemical Abundances in Clusters of

We study the origin of iron and-elements (O, Mg, Si) in clusters of galaxies. In particular, we discuss the O/Fe] ratio and the iron mass-to-luminosity ratio in the intracluster medium (ICM) and their link to the chemical and dynamical evolution of elliptical and lenticular galaxies. We adopt a detailed model of galactic evolution incorporating the development of supernovae-driven galactic wind...

Chemical Fractionation and Abundances in Coronal Plasma

Much of modern astrophysics is grounded on the observed chemical compositions of stars and the diffuse plasma that pervades the space between stars, galaxies and clusters of galaxies. X-ray and EUV spectra of the hot plasma in the outer atmospheres of stars have demonstrated that these environments are subject to chemical fractionation in which the abundances of elements can be enhanced and dep...

Plant Growth Control: Biological, Chemical, Physical and Post-harvest Parameters