A general overview of the physical properties of the HII regions is presented here, emphasizing the various general models made to explain their structure and behaviour. The Lyman continuum effective extinction, representing a measure of the extinguished or lost fraction of the ionizing flux, is explained briefly, and the results of a study

We present observations of the magnetic landscape of the polar region of the Sun that are unprecedented in terms of spatial resolution, field of view, and polarimetric precision. They were carried out with the Solar Optical Telescope aboard Hinode. Using a Milne-Eddington inversion, we find many vertically oriented magnetic flux tubes with field

Context: Over the past decade there have been a series of results supporting the hypothesis of the existence of a long thin bar in the Milky Way with a half-length of 4.5 kpc and a position angle of around 45°. This is apparently a very different structure from the triaxial bulge of the Galaxy, which is thicker and shorter and dominates the star

Aims: Previous studies have indicated that faint and bright early-type galaxies (ETGs) present different coefficients and dispersions for their Kormendy relation (KR). A recently published paper states that the intrinsic dispersion of the KR depends on the magnitude range within which the galaxies are contained, therefore we investigate here

GM 24 is a compact nebulous object immersed in the low-brightness HII region RCW 126. It is associated with a warm and dense CO cloud at whose centre a deeply embedded (A_V = 55) massive cluster of more than one hundred members is located. The most luminous young stellar object of the cluster, Irs 3 (= IRAS 17136-3617), radiates most of its energy

We present an extragalactic perspective of an extended stellar tidal stream wrapping around the edge-on spiral galaxy NGC 5907. Our deep images reveal for the first time a large-scale complex of arcing loops that is an excellent example of how low-mass satellite accretion can produce an interwoven, rosette-like structure of debris dispersed in the