The accepted explanation of the observed dichotomy of two orders of magnitude between in situ measurements of electron density in H II regions, derived from emission line ratios, and average measurements based on integrated emission measure, is the inhomogeneity of the ionized medium. This is expressed as a ``filling factor", the volume ratio of

Aims: Proper motion measurements of the cool and ultracool populations in the Upper Scorpius OB association are crucial to confirm membership and to identify possible run-away objects. Methods: We cross-match samples of photometrically selected and spectroscopically confirmed cool and ultracool (K5 SpT M8.5) candidate members in the Upper

Aims: We study the properties of solar granulation in a facular region from the photosphere up to the lower chromosphere. Our aim is to investigate the dependence of granular structure on magnetic field strength. Methods: We used observations obtained at the German Vacuum Tower Telescope (Observatorio del Teide, Tenerife) using two different

The Local Group galaxies enable us to study the impact of metallicity on the structure and evolution of massive stars through spectroscopic analyses. However, color-based target selection for spectroscopy (in absence of known spectral types), though relatively successful, usually produces lists dominated by B-type modest-mass stars. We have

We describe a simple step-by-step guide to qualitative interpretation of galaxy spectra. Rather than an alternative to existing automated tools, it is put forward as an instrument for quick-look analysis and for gaining physical insight when interpreting the outputs provided by automated tools. Though the recipe is for general application, it was

The seemingly un-magnetized part of the solar surface is not really un-magnetized. It is occupied by magnetic structures producing low polarization which, therefore, escape detection in traditional measurements. Since most of the solar surface belongs to this category, the quiet Sun magnetic fields can easily carry most of the magnetic flux and