We present new high quality continuum-subtracted Hα images of the grand-design galaxies NGC 157, NGC 3631, NGC 6764 and NGC 6951. We have determined the positions, angular sizes, and fluxes of their individual HII regions, and describe statistical properties of the HII region samples. We construct luminosity functions for all the HII regions in the

QUE94281, the newest basaltic lunar meteorite, is a complex regolith breccia with abundant glass. This glass occurs in a variety of forms and compositions; fusion crust, splash glass coating, glass veins and glass beads. In both mineralogy and composition the breccia is intermediate between highland and mare rocks, but closer to mare samples. It is

This paper presents some numerical results relative to a solution, based on the density matrix formalism, of the non-LTE, polarized radiative transfer problem for a two-level atom. The results concern the atomic upper level population and alignment, and the emergent radiation Stokes profiles, for a plane-parallel, static, isothermal atmosphere

We have acquired low- and intermediate-resolution spectroscopy at 11 positions across the nucleus of NGC 6210. As a consequence, we are able to map the variation of velocity, temperature, line excitation, and density over the projected core and halo of this source. Temperatures reach a peak value Te≌1.1×104K close to the nucleus, and thereafter

The net circular polarization in a spectral line due to the combined effect of magnetic fields and velocity gradients is analyzed for a few schematic situations. In some particular cases, its dependence on the magnetic field, velocity field and line parameters can be expressed analytically.

Asymmetrical Stokes profiles are produced if the photospheric magnetic and velocity fields are structured on scales smaller than the mean-free-path of the photons. Here we put forward a compact analytical expression for the radiative transfer equation in this case. Explicitly, micro-variations of the magnetic field strength and the velocity are