At Paranal Observatory in the YEPUN (UT4) telescope, two instruments are installed and equipped with adaptive optics systems: an infrared spectro imager (CONICA) below the adaptive optics module NAOS; and an integral field spectrograph (SINFONI). In the same telescope, the Laser Guide Star Facility (LGSF) is installed to provide a reference star to

Context. The mechanisms giving rise to diffuse radio emission in galaxy clusters, and in particular their connection with cluster mergers, are still debated. Aims: We seek to explore the internal dynamics of the cluster Abell 2294, which has been shown to host a radio halo. Methods: Our analysis is mainly based on redshift data for 88 galaxies

We present measurements of the atmospheric water vapour content above the Roque de los Muchachos Observatory (ORM) obtained using the Global Positioning System (GPS). The GPS measurements have been evaluated by comparison with 940-nm radiometer observations. A statistical analysis of the GPS measurements points to the ORM as an observing site with

The back-reaction of baryons on the dark matter halo density profile is of great interest, not least because it is an important systematic uncertainty when attempting to detect the dark matter. Here, we draw on a large suite of high-resolution cosmological hydrodynamical simulations to systematically investigate this process and its dependence on

Context. The image degradation produced by atmospheric turbulence and optical aberrations is usually alleviated using post-facto image reconstruction techniques, even when observing with adaptive optics systems. Aims: These techniques rely on the development of the wavefront using Zernike functions and the non-linear optimization of a certain

In this paper, we present an original observational approach, which combines, for the first time, traditional speckle imaging with image post-processing to obtain in the optical domain diffraction-limited images with high contrast (10-5) within 0.5 to 2 arcseconds around a bright star. The post-processing step is based on wavelet filtering an has