My main research interests are the nature and properties of the first stars and galaxies that form in the Universe. I am particularly interested in understanding how the radiation emitted by the first stars and the heavy elements that the first supernova explosions release in the interstellar medium change their environmental properties, leading to the ever-increasing complexity of the modern Universe.
I list below some of the research topics that I am currently working on:
The rise of dust in the Universe:
Dust grains are a fundamental constituent of the interstellar medium (ISM) of galaxies. Their presence dramatically affects the thermal and chemical properties of the ISM as well as the appearance of stars and galaxies, absorbing their UV and optical radiation and re-emitting it at longer wavelengths. Dust grains are formed in the cooling ejecta of supernovae and in the winds of intermediate mass stars, when they enter the Asymptiotic Giant Branch (AGB) phase. When released in the ISM, the grains are destroyed by interstellar shocks and modified by additional physical processes that occur in the cold phase of the ISM. With a large number of collaborators, we are investigating different aspects of this problem, including the formation of grains by stars of different masses and metallicity, chemical evolution models with dust, numerical simulations of early dust enrichment in the high redshift Universe, the impact of dust grains on the nature of stellar populations. If you are interested, you can give a look to the recent review that I wrote with Roberto Maiolino.
The early growth of the first supermassive black holes:
The existence of quasars at z up to 7.54 shows that rapid formation and growth of black holes up to masses of several billion solar mass must have occurred in the early Universe. JWST is now observing super-massive black holes out to z ≈ 10 and has unveiled a new population of active galactic nuclei at 4 < z < 6 with very unexpected properties which challenge theoretical models. Understanding the growth of these monsters black holes and their relation with galaxy evolution is currently one of the hottest topics in astrophysics. With my collaborations, we are exploring different aspects of this problem, ranging from the nature of the first black hole seeds, their dominant growth mode, their observational features in the electromagnetic and gravitational wave bands.
Compact binary systems in the Local Group:
In addition to massive and supermassive black holes, compact binary systems represent a very important class of astrophysical sources. They have been the first to be detected in gravitational waves by the LVK collaboration during the first two observing runs, and many more are expected to be discovered in the future. While it is not yet clear whether the systems that have been observed in gravitational waves so far have formed from field binary stars or through dynamical interactions in dense stellar systems, the first discoveries have made clear that in order to leave sufficiently massive black hole remnants, the parent stellar populations have to form at low metallicity. With my collaborators, we are exploring the formation and merger rates of different classes of bynary systems in a simulation of the Local Group that allows to describe in great detail the properties of low metallicity star forming regions. These studies can be used for a number of different purposes, including predictions and interpretation of current and future gravitational wave data, reionization and heating of the interstellar medium during the evolution of the Milky Way and its satellite galaxies, chemical evolution of neutron-capture elements.