Gravitational lenses and dark matter (Director: Marco Lombardi)
Progress in this relatively new and unexplored field through theory and observations has been extremely rapid during the last decades and theenormous amount of work produced on gravitational lensing has demonstrated its strength and its potential for future astrophysical applications. Black holes in astrophysics (Director: Monica Colpi) Black holes are among the most mysterious objects that the human mind has been capable of imagining. Discovered as pure mathematical entities, black holes for long time have been considered tools for exploiting the nature of gravity. Nowadays, black holes are believed to be genuine astrophysical sources. According to the no-hair theorem, a black hole is an elementary object specified uniquely by its mass and angular momentum (or spin). Thus, one of the main goals of current astronomical investigations, is the measure of the mass and spin of the astrophysical black holes, in relation to their cosmic evolution. Since the early discovery of quasars, the accretion paradigm has been at the heart of the interpretation of supermassive black holes as being real sources in the universe. It was also recognized that the luminous quasars were undergoing strong cosmic evolution: nuclear activity was common in the past and declined with cosmic time. In addition, there has been always the suspicion that at high redshift accretion was ignited in many if not all galaxies, leading to the commonly held premise that most galaxies we see in our local universe should host in their nucleus a massive black hole, relic of an earlier active phase. Today, due largely to the impact of ground-based telescopes and of the Hubble Space Telescope, the mass of quiescent black holes inside the cores of nearby galaxies including our own Milky Way, has been measured using stars and/or gas clouds as dynamical probes. Now there is indeed strong circumstantial evidence that massive black holes are ubiquitous in spheroids. Astronomers discovered in addition, the existence of tight correlations between the black hole mass and the large scale properties of the underlying host. It is currently believed that during the formation of galaxies, a universal mechanism was at play able to deposit, in the nuclear regions, large amounts of gas to fuel the black hole to such an extent that its feedback, i.e. its large-scale energy/momentum injection, had blown the gas out, thus sterilizing the galaxy against further star formation, and that major galaxy mergers could be at the heart of this symbiotic relationship. The coevolution of black hole and galaxies embraces today a variety of astrophysical phenomena that are now becoming of major scientic interest. They go from the formation of black hole in the rst pre-galactic structures, to black hole growth and feedback in major gas-rich mergers. But not only. A new and critical aspect of this concordant evolution is the formation of massive black hole binaries that will eventually coalesce becoming the loudest sources of gravitational waves that upcoming gravitational wave observatories will be able to detect out to very large redshift, when the universe was less than a few hundred million years old. These waves carry information on the black hole spins and masses that will be measured with astonishing precision. Since coalescing binary black holes are standard sirens there is also the hope to use them as a tool for measuring the dark-energy equation of state and possibly its evolution. All these hot topics will be presented in this School to provide a comprehensive view of the impact that the astrophysics of black holes can have on our knowledge of the universe. |  The gravitational lensing system SDSS J1538+5817, before (left) and after (right) the subtraction of an elliptical model for the lens galaxy.   |
