The extragalactic background light at far-infrared ( FIR) wavelengths comes from optically faint, dusty, star-forming galaxies in the Universe with star formation rates of a few hundred solar masses per year. These faint, submillimetre galaxies are challenging to study individually because of the relatively poor spatial resolution of far-infrared telescopes but they are responsible for more than 85% of the total extragalactic intensity at these wavelengths. Instead, their average properties can be studied using statistics such as the angular power spectrum of the background intensity

We find a distinct stellar population in the counterrotating and kinematically decoupled core of the isolated massive elliptical galaxy NGC 1700. Coinciding with the edge of this core, we find a significant change in the slope of the gradient of various representative absorption line indices. Our age estimate for this core is markedly younger than the main body of the galaxy. We find lower values for the age, metallicity, and Mg/Fe abundance ratio in the center of this galaxy when we compare them with other isolated elliptical galaxies with similar velocity dispersion. We discuss the

We have selected the Galactic HII region M43, a close-by apparently spherical nebula ionized by a single star (HD37061, B0.5V) to investigate several topics of recent interest in the field of HII regions and massive stars. We perform a combined, comprehensive study of the nebula and its ionizing star by using as many observational constraints as possible. For this study we collected a set of high-quality observations, including the optical spectrum of HD3706, along with nebular optical imaging and long-slit spatially resolved spectroscopy. On the one hand, we have carried out a quantitative

Delta Scuti (δ Sct) stars are opacity-driven pulsators with masses of 1.5-2.5M⊙, their pulsations resulting from the varying ionization of helium. In less massive stars such as the Sun, convection transports mass and energy through the outer 30 per cent of the star and excites a rich spectrum of resonant acoustic modes. Based on the solar example, withno firm theoretical basis, models predict that the convective envelope in δ Sct stars extends only about 1 per cent of the radius, but with sufficient energy to excite solar-like oscillations. This was not observed before the Kepler mission, so

Las binarias de rayos X son sistemas formados por un objeto compacto (estrella de neutrones o agujero negro) y una estrella de tipo “normal”. El objeto compacto arranca materia de la estrella que orbita alrededor del objeto compacto formando un disco de acreción. Las binarias de rayos X transitorias son un tipo de binarias de rayos X que se caracterizan por estar la mayor parte de su vida en quietud. Ocasionalmente, el sistema entra en erupción, fenómeno relacionado con un brusco aumento del ritmo de acreción de materia sobre el agujero negro. Este aumento de brillo se produce en todas las

A large fraction of planetary nebulae (about 80%) are bipolar or elliptical rather than spherically symmetric. Modern theories invoke magnetic fields, among other causes, to explain the rich variety of aspherical components observed in planetary nebulae (PNe), as ejected matter is trapped along magnetic field lines. But, until recently, this idea was mostly a theoretical claim. But in 2005, Jordan et al. report the detection of kG magnetic fields in the central star of two non-spherical PNe, namely NGC1360 and LSS1362. They observed the circular polarization spectra of these stars with the