Because of the intense brightness of the OB-type multiple star system σ Ori, the low-mass stellar and substellar populations close to the centre of the very young σ Orionis cluster is poorly know. I present an IJHK_s survey in the cluster centre, able to detect from the massive early-type stars down to cluster members below the deuterium burning

Many barred galaxies show a set of symmetric enhancements at the ends of the stellar bar, called ansae, or the "handles" of the bar. Ansa bars have been in the literature for some decades, but their origin has still not been specifically addressed, although they could be related to the growth process of bars. But even though ansae have been known

Context: Planetary Nebulae (PNe) display complex radial surface brightness profiles whose understanding is crucial for a correct interpretation of their formation and evolution. In particular, the intermediate shells commonly observed around the bright rims of PNe contain important information for the discussion of the mass loss rate at the end of

Sources responsible for volcanic unrest produce characteristic surface deformation. Given a sufficient number of distributed observation points, inversion is the preferred procedure for retrieving the source parameters of location and volume or pressure change. Most often the solutions have been for point sources embedded in a homogeneous half

We present reliable measurements of the metallicity distribution function (MDF) at different points along the tidal stream of the Sagittarius (Sgr) dwarf spheroidal (dSph) galaxy, based on high-resolution, echelle spectroscopy of candidate M giant members of the Sgr system. The Sgr MDF is found to evolve significantly from a median [Fe/H]~-0.4 in

We present Keck/LRIS optical spectroscopy of 35 z>=1.4 luminous IR galaxies in the Spitzer Wide-area Infra-Red Extragalactic survey (SWIRE) northern fields (Lockman Hole, ELAIS-N1, ELAIS-N2). The primary targets belong to the "IR-peak" class of galaxies, having the 1.6{mu}m (restframe) stellar feature detected in the IRAC Spitzer channels. The