Context. The nature of ultra-luminous X-ray (ULX) sources is still a matter of debate. Studies of their counterparts in other spectral ranges will help to clarify the nature of those sources. Aims: Our goal was to identify and characterize the optical counterparts of five sources catalogued as ULXs. Methods: We obtained optical imaging and

Some recent observations seem to disagree with hierarchical theories of galaxy formation about the role played by major mergers in the late buildup of massive E-S0s. We re-address this question by analysing the morphology, structural distortion level and star formation enhancement of a sample of massive galaxies (M* > 5 × 1010 M&sun;) lying on the

We present new observational determination of the evolution of the rest-frame 70 and 160 μm and total infrared (TIR) galaxy luminosity functions (LFs) using 70 and 160 μm data from the Spitzer Wide-area Infrared Extragalactic (SWIRE) Legacy survey. The LFs were constructed for sources with spectroscopic redshifts only in the XMM-LSS and Lockman

Present-day massive galaxies are composed mostly of early-type objects. It is unknown whether this was also the case at higher redshifts. In a hierarchical assembling scenario the morphological content of the massive population is expected to change with time from disc-like objects in the early Universe to spheroid-like galaxies at present. In this

The mass of a galaxy is the most important parameter to understand its structure and evolution. The total mass we can infer by constructing dynamical models that fit the motion of the stars and gas in the galaxy. The dark matter content then follows after subtracting the luminous matter inferred from colors and/or spectra. Here, we present the mass

Recent success in explaining several properties of the dusty torus around the central engine of active galactic nuclei has been gathered with the assumption of clumpiness. The properties of such clumpy dusty tori can be inferred by analysing spectral energy distributions (SEDs), sometimes with scarce sampling given that large aperture telescopes