Progetti di ricerca

Gravitational-wave (GW) Astronomy opened a new window to the Universe from its infant state to the present. The key physical systems which allow probing the Universe through these vast time and length scales are Black Holes (BH). Low metallicity clouds, composed primarily… Leggi tutto of atomic hydrogen, before and during the epoch of reionization, are a natural environment for BHs to be born and form Binary Black Holes (BBH) which can merge via GW emission. Stellar BHs, being the remnants of the death of very massive stars, are generated early when a huge gas reservoir is available for accretion. Mass segregation leads the BHs close to the center of the system and a dense BH-subcluster, supported by gravitational fluctuations, is formed. The low metallicity of the gas suppresses cooling, while turbulence of the gas and the BHs’ motion further favor quasi-spherical accretion, surpassing the Eddington limit. For sufficiently compact configurations, the BHs shall grow in mass before the gas is depleted by stellar evolution and formation feedback processes. This rapid mass growth through turbulent hot accretion shall leave a distinct spin signature on the BHs. The BBH that accrete gas quasi-spherically may harden if there is not significant angular momentum loss from the system. Furthermore, these are also ideal conditions for high-redshift Intermediate Mass Black Holes (IMBH) to form. We shall calculate the spin distribution of stellar BHs accreting gas in proto-clusters, calculate the BH mass function following such accretion events, investigate the evolution of separation in accreting BBH in low-metallicity hot turbulent gas, develop theoretical models for the evolution of a BH-subcluster inside proto-clusters and investigate the formation of IMBH. Finally, we shall develop methods for identifying the origin of GW observations, confront our results with LIGO-Virgo-KAGRA data, and investigate synergetically the implications for the GW mission LISA and the X-ray mission Athena.

Gravitational-wave astronomy is entering its large-statistics regime. Catalogs with thousands of gravitational-wave events will soon be available, providing a wealth of information on the most compact objects in the Universe --black holes and neutron stars. These new datasets need new tools to… Leggi tutto be exploited effectively in order to maximize their scientific impact. GWmining is an ambitious program to explore upcoming gravitational-wave catalogs with data-mining techniques. We will develop a complete framework to analyze gravitational-wave data in light of astrophysical predictions. Going beyond phenomenological models, we will train machine-learning algorithms directly on large banks of populationsynthesis simulations and post-Newtonian integrations. The development of these astrophysical predictions requires new modeling strategies to accurately capture all the gravitational-wave observables, notably spins and eccentricities. Combined with a hierarchical Bayesian analysis, our neural network will deliver the most stringent measurements to date on elusive phenomena influencing the lives of massive stars. We will constrain phenomena such as binary common envelope, supernova kicks, stellar winds, tidal interactions, etc. Besides harnessing the catalog in its entirety, our complete framework will put us at the forefront to analyze outliers -- golden events with favorable properties of one or more parameters. We will design a complete strategy to exploit the strongest signals to infer exquisite details of the relativistic dynamics of their sources. GWmining is a unique project strategically placed at the intersection of astronomy, data analysis, and relativity. As the large-statistics revolution of gravitational-wave astronomy unfolds, GWmining will pioneer the application of datamining techniques in gravitational-wave population studies, setting the foundations of this booming field for decades.

The direct detection of gravitational waves from binary stellar-mass black hole systems in our Universe provides a wealth of astrophysical information which is now within our reach. These binaries merge in the LIGO and Virgo detector frequency sensitivity bands, and were once… Leggi tutto sweeping through the LISA band, emitting at much lower frequencies. In LIGO, the binary mergers appear both as single, resolved events and as a multitude of incoherent signals, known as the stochastic gravitational-wave background. In LISA, a similar picture will be seen, where a few binaries are directly resolved, while the vast majority build up a stochastic signal. With StochRewind, we will draw out all binary black hole information measured by LIGO and Virgo to calibrate the LISA mission, providing a crucial ingredient for LISA data analysis methods. First, we focus on the stochastic background in LIGO, and deliver a brand new pipeline which maximises our chances for detection. Then, we analyse the implications of the LIGO black hole detections and stochastic background for LISA, delivering the first data-based prediction of the LISA binary black hole stochastic background, fully exploiting our multi-band gravitational-wave knowledge. It is essential that StochRewind be hosted by an institute which can supplement the fellow's first-hand experience in stochastic LIGO data analysis with knowledge on black hole population analysis and LISA astrophysics. UniMiB is a unique institution which counts top experts in both these fields, providing an environment which bridges the gap between LISA and LIGO. These revolutionary science objectives will be paired with advanced training objectives tailored to the fellow's personal career development plan, rooted in what UniMiB and the collaborations have to offer. StochRewind will have far-reaching impacts on the community, which will reap the benefits for decades to come.