Massive galaxy clusters are interesting astrophysical and cosmological objects to study, but they are relatively rare. In the redshift range z = 0.25-0.5 which is, for example, a favourable region for gravitational lensing studies, about 100 such systems are known. Most of them have been studied in X-rays. In this paper we study the six remaining

Context. The young massive cluster Westerlund 1 offers the promise of a grand laboratory for the study of high-mass star evolution, but its basic parameters are still poorly known. Aims: In this paper, we aim at a better characterisation of the cluster by determining some basic kinematic properties and analysing the area surrounding the cluster and

Context. The outer Galactic disc contains some features such as the warp and flare, whose origin is still debated. The Gaia data provide an excellent opportunity to probe the Galactic disc at large distances and study these features. Aims: We derive the density distributions of the average (old) whole population and the supergiants (representative

Volume Phase Holographic Gratings (VPHGs) are optical element widely used in astronomical spectrographs as main disperser or cross-disperser in high resolution echelle instruments. In spite of the fact that other technologies are available on the market, the VPH technology remain a key one. In the EU funded OPTICON project, different activities

We use the suite of Milky Way-like galaxies in the Auriga simulations to determine the contribution to annihilation radiation from dark matter subhalos in three velocity-dependent dark matter annihilation models: Sommerfeld, p-wave, and d-wave models. We compare these to the corresponding distribution in the velocity-independent s-wave annihilation

We measure the velocity dispersions of clusters of galaxies selected by the red-sequence Matched-filter Probabilistic Percolation (redMaPPer) algorithm in the first three years of data from the Dark Energy Survey (DES), allowing us to probe cluster selection and richness estimation, λ, in light of cluster dynamics. Our sample consists of 126