In this thesis we have studied three independent tools to get information on cosmological parameters: the large scale structure (LSS) of matter in the Universe, galaxy clusters and the cosmic microwave background (CMB). In the study of the LSS we have provided an analytical recipe for computing the conditional mass function (CMF), i.e. the mass

The discovery of γ-ray emission from radio-loud narrow-line Seyfert 1 (NLSy1) galaxies has questioned the need for large black hole masses ( ≳ 108 M⊙) to launch relativistic jets. We present near-infrared data of the γ-ray-emitting NLSy1 FBQS J1644+2619 that were collected using the camera CIRCE (Canarias InfraRed Camera Experiment) at the 10.4-m

We identify six ultra-diffuse galaxies (UDGs) outside clusters in three nearby isolated groups (0.014 z 0.026) using very deep imaging in three different Sloan Digital Sky Survey filters (g, r and I bands) from the IAC Stripe 82 Legacy Project. By comparing with the abundance of UDGs in rich galaxy clusters, we find that the density of UDGs (i.e

Context. Stellar rotation affects the transport of chemical elements and angular momentum and is therefore a key process during stellar evolution, which is still not fully understood. This is especially true for massive OB-type stars, which are important for the chemical enrichment of the Universe. It is therefore important to constrain the

Context. Quantifying the number, type, and distribution of Wolf-Rayet (W-R) stars is a key component in the context of galaxy evolution, since they put constraints on the age of the star formation bursts. Nearby galaxies (distances ≲5 Mpc) are particularly relevant in this context since they fill the gap between studies in the Local Group, where

A spectroscopic analysis has been undertaken for the B-type multiple systems (excluding those with supergiant primaries) in the VLT-FLAMES Tarantula Survey (VFTS). Projected rotational velocities, vesini, for the primaries have been estimated using a Fourier Transform technique and confirmed by fitting rotationally broadened profiles. A subset of