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There is substantial evidence for a connection between star formation in the nuclear region of a galaxy and growth of the central supermassive black hole. Furthermore, starburst activity in the region around an active galactic nucleus (AGN)…
A thorough study of radio emission in Active Galactic Nuclei (AGN) is of fundamental importance to understand the physical mechanisms responsible for the emission and the interplay between accretion and ejection processes. High frequency…
Growing supermassive black holes (Active Galactic Nuclei; AGN) release energy with the potential to alter their host galaxies and larger-scale environment; a process named "AGN feedback". Feedback is a required component of galaxy formation…
The physical quantity that directly controls the feedback of active galactic nuclei (AGNs) in elliptical galaxies remains to be determined. The discovery of molecular gas around the AGNs suggests that the gas is fueling the AGNs. Therefore,…
We combine Very-Long-Baseline Interferometry (VLBI) data for $\sim100$ active galactic nuclei (AGN) available from the Very Large Baseline Array (VLBA) 2 cm imaging survey and optical spectroscopy to investigate the relationships in the…
The centre of our galaxy hosts the nearest super-massive black hole to the solar system, identified to the compact radio source Sgr A*. High energy experiments have tried in the past to detect the X/gamma-ray emission expected from the…
The unexpectedly high nitrogen-to-oxygen (N/O) ratios observed in high-redshift (z) galaxies have challenged our understanding of early star formation. Notably, many of these nitrogen-rich galaxies show signatures of active galactic nuclei…
Centaurus A (Cen A) is the closest radio galaxy and a prime example of a low-luminosity active galactic nucleus (AGN), exhibiting complex emissions across the electromagnetic spectrum. The nature of its continuum emission, particularly the…
The underlying hypothesis of this work is that the active galactic nuclei (AGNs) are wormhole mouths rather than supermassive black holes (SMBHs). Under some - quite general - assumptions such wormholes may emit gamma radiation as a result…
Superluminal motion is a common feature of radio jets in powerful gamma-ray emitting active galactic nuclei. Conventionally, the variable emission is assumed to originate near the central supermassive black-hole where the jet is launched on…
A detailed multi-messenger study of the high-energy emission from the Galactic plane is possible nowadays thanks to the observations provided by gamma and neutrino telescopes and could be mandatory in order to obtain a consistent scenario.…
The supermassive black hole at the Galactic center, Sagittarius A*, has experienced periods of higher activity in the past. The reflection of these past outbursts is observed in the molecular material surrounding the black hole but…
Accreting black holes and neutron stars release an unknown fraction of the infalling particles and energy in the form of collimated jets. The jets themselves are radiatively inefficient, but their power can be constrained by observing their…
The first high-energy neutrino source identified by IceCube was a blazar -- an active galactic nucleus driving a relativistic jet towards Earth. Jets driven by accreting black holes are commonly assumed to be needed for high-energy neutrino…
The high kinetic energy outflowing in the jets of microquasars is delivered to the surrounding interstellar medium. This energy input can cause the formation of bow shocks and cocoons that may be detectable from radio to gamma-ray energies.…
Centaurus A, the closest active galaxy, has been detected from radio to high-energy gamma-rays. The synchrotron radiation by extremely high energy protons may be a suitable mechanism to explain the MeV to GeV emission detected by the…
The origin of high-energy cosmic rays, atomic nuclei that continuously impact Earth's atmosphere, has been a mystery for over a century. Due to deflection in interstellar magnetic fields, cosmic rays from the Milky Way arrive at Earth from…
High-energy neutrinos and photons are complementary messengers, probing violent astrophysical processes and structural evolution of the Universe. X-ray and neutrino observations jointly constrain conditions in active galactic nuclei (AGN)…
Using archival Chandra observations of 19 LINERs we explore the X-ray properties of their inner kiloparsec to determine the origin of their nuclear X-ray emission, to investigate the presence of an AGN, and to identify the power source of…
The radio emission mechanism in active galactic nuclei (AGN) with high accretion rates is unclear. It has been suggested that low-power jets may explain the observed radiation at sub-parsec scales. The mechanisms for jet formation at…