the most dark matter dominated ones that we can observe, these nearby dwarf galaxies are widely considered as precious systems to shed light on the processes that drive galaxy formation and evolution at small halo masses. Nonetheless, the majority of them are found in the surrounding of a much larger system, i.e. the Milky Way or M31; this makes the knowledge of the orbits around the host a crucial piece of information for investigating the role of environment in shaping the dwarf galaxies' observed properties. In addition, this type of information can also be used to improve our understanding of the Milky Way itself, e.g. its dark matter halo mass. In this talk I will present the results of recent works, in which the exquisite astrometric data from the ESA Gaia mission are used to provide the missing information on the systemic proper motions for the majority of Local Group dwarf galaxies, out to 1.4Mpc. I will then discuss the orbital properties determined for the galaxies within 500 kpc from the Milky Way in the context of dwarf galaxies's group infall onto the Milky Way, implications for the too-big-to-fail problem, tidal disruption from the Milky Way, as well as determinations of the Milky Way mass.

is in fact a key ingredient driving the thermal evolution of galaxy groups/clusters and, in turn, the evolution of galaxies in the universe over cosmic times. In these years the unprecedented sensitivities provided by SKA precursors/pathfinders are significantly pushing forward the study of the jet life-cycle and the jets’ interaction with the external medium. In this talk I will present some recent results we obtained in this field using observations at MHz-frequencies, which are especially suited to unveil the oldest populations of particles injected by AGN jets in their surrounding environment. In particular, the study of this so-called ‘AGN remnant plasma’ has allowed us to trace the black hole’s activity back in time and to follow the interaction/mixing of the AGN jet plasma with the surrounding medium up to hundreds of million years, with a unique level of detail for the first time.

since the first detection in 2015, more and more astrophysical sources have been discovered through gravitational-waves. After three observing runs, the LIGO and Virgo collaborations have observed almost 100 compact binaries coalescences, including binary black holes and binary neutron star mergers. GWs observations can be employed to study many of the open questions in current physics such as : Is general relativity valid on cosmological scales? Is there a massive graviton? How fast the Universe is expanding? What is the formation channel of binary black holes? In this seminar I will show how GW sources can address these questions and also potentially introduce systematic biases in this kind of studies. After reminding how GWs are generated from compact binaries and detected by ground-based detectors, I will highlight how astrophysical information on the sources are imprinted in their GW emission. Then, I will show how GWs from compact objects provide a ''standard siren'', a new way to measure cosmic distances, which can be used to measure cosmological parameters, such as the Hubble constant. I will then discuss how GWs can be used to test General relativity, in particular to test the nature of Dark Energy and the presence of a possible massive gravition. I will conclude by showing how populations of GWs sources can be studied to infer the formation channels of compact binaries systems.

truly began with the discovery of a GRB linked to a Gravitational Wave, establishing short-duration GRBs as binary mergers of compact objects. I will present the physics of GRB afterglows, discuss the afterglows of short vs. long GRBs, and present the difficulties of localizing Gravitational Wave sources via their electromagnetic afterglow emission.

space: the so-called high-α sequence, classically associated to an old population of stars in the thick disc, and the low-α sequence, which mostly comprises relatively young stars in the thin disc. We perform a Bayesian analysis based on a MCMC method to constrain a multi-zone two-infall chemical evolution model designed for regions at different Galactocentric distances using measured chemical abundances from the APOGEE DR16 sample. In the outer disc (with radii R>6 kpc), the chemical dilution due to a late accretion event of gas with primordial chemical composition is the main driver of the [Mg/Fe] vs. [Fe/H] abundance pattern in the low-α sequence. In the inner disc, in the framework of the two-infall model , we confirm the presence of an enriched gas infall in the low-α phase as suggested by chemo-dynamical models. Our Bayesian analysis of the recent APOGEE DR16 data suggests a significant delay time, ranging from ∼3.0 to 4.7 Gyr, between the first and second gas infall events for all the analyzed Galactocentric regions, confirming the findings of previous works for the solar neighbourhood based on the APOKASC data. Recent results for the vertical distribution of the [Mg/Fe] abundance ratio in the solar neighborhood will be also discussed. In the second part of my talk, I will show results related to the azimuthal variation of abundance gradients in the Milky Way. We quantify the effects of spiral arm density fluctuations on the azimuthal variations of the oxygen abundances in the Galactic disk. We interpret the presence of azimuthal scatter at all radii by the presence of multiple spiral modes moving at different pattern speeds.