Guidetta Torricelli
Broad Line Region structure
Recent studies on X-ray absorption variability on time scales of hours/days demonstrate that the X-ray "torus" is made of clouds with the same density and distance from the center as the BLR emission line clouds, thus suggesting a close link between the BLR and the X-ray circumnuclear absorber. Until now, this approach has been applied to a small number of cases. However, more long X-ray observations of bright sources with XMM-Newton and Suzaku, suitable for absorption variability analysis, are present in public archives and hence this X-ray absorption analysis can be applied to other sources. The idea is that the results of these observational studies will be fundamental for a better physical description of the absorbers and, therefore,for a better knowledge of the actual structure of the BLR. The analysis is in progress.
Research on AGN
The formation and evolution of Active Galactic Nuclei (AGN), attributed to accreting massive black holes (BHs), are closely related to the formation and evolution of the galaxies which host them. Our group has been studying the co-evolution of AGN, BHs, and their host galaxies for several years now. We rely on a multiwavelength approach, from the millimeter and the IR to the X-ray. Specifically, our group is engaged in studies of:
- The structure and properties of the circumnuclear medium of AGN and radio galaxies, with application to AGN unification (Susanna Bisogni, Giovanni Cresci, Sperello di Serego Alighieri, Alessandro Marconi, Filippo Mannucci, Guido Risaliti, Marco Salvati, Guidetta Torricelli)
- The primary and reflected X-ray emission of AGN, including the analysis of General Relativity effects, and the measurement of the spin of the central supermassive black holes (Elisabeta Lusso, Guido Risaliti)
- Spectral energy distributions of AGN, with particular regard to bolometric corrections, the extreme IR spectral region, and the AGN contribution to the cosmic background (Elisabeta Lusso, Alessandro Marconi, Guido Risaliti, Marco Salvati)
- Scaling relations between BH mass and host galaxies properties (local AGN, QSOs, and non-AGN) in the context of formation and co-evolution scenarios (Stefano Carniani, Leslie Hunt, Alessandro Marconi, Guido Risaliti, Stefano Zibetti)
- Diagnostics of AGN and starburst components in Ultraluminous and Luminous Infrared Galaxies (ULIRGs and LIRGs) through hard X-ray and infrared spectroscopy of dust features (Alessandro Marconi, Guido Risaliti, Marco Salvati)
- AGN fueling mechanisms and relation to star formation through morphology and dynamics of circumnuclear molecular gas (Stefano Carniani; NUGA: Viviana Casasola, Leslie Hunt)
- AGN outflows and the effects of AGN feedback on host galaxies (Giovanni Cresci, Alessandro Marconi)
- Studies of the AGN population with deep surveys in the X-ray and radio bands (Guido Risaliti, Paolo Tozzi)
Research on the LOCAL UNIVERSE
Galaxy evolution is occurring at the present epoch in the Local Universe, through gas accretion and gas consumption via star formation, or through passive evolution. Evolutionary processes can be studied in nearby galaxies with a detail that high-redshift objects do not allow. We rely on a multiwavelength approach and comparison with theoretical predictions; special attention is given to the interstellar medium of star-forming and quiescent galaxies and how its properties vary with galaxy mass, metallicity, and environment. The ultimate aim is to exploit studies of nearby galaxies in the cosmological context to better understand how galaxies form and evolve. Specifically, our group is engaged in studies of:
- Star formation processes in the Local Group (Viviana Casasola, Edvige Corbelli, Carlo Giovanardi, Laura Magrini)
- Gas and dust content and radiation transfer modeling of nearby spirals (Simone Bianchi, Marco Bocchio, Viviana Casasola, Edvige Corbelli, Carlo Giovanardi, Leslie Hunt)
- Stellar mass in galaxies: its measurement and its effects (Anna Gallazzi, Leslie Hunt, Stefano Zibetti)
- Dark matter, gas and satellite accretion in galaxies (Edvige Corbelli, Stefano Zibetti)
- ISM properties of early type galaxies (Sperello di Serego Alighieri, Carlo Giovanardi)
- Stellar populations in galaxies (age and chemical abundance) and their dependance on galaxy mass and environment (Anna Gallazzi)
- Radial metallicity gradients in disk galaxies: shape and time evolution (Viviana Casasola, Edvige Corbelli, Laura Magrini)
- Integral-field spectroscopic survey of nearby galaxies CALIFA (Anna Gallazzi, Stefano Zibetti)
- Dust features and ISM components of star-forming metal-poor dwarf galaxies (Leslie Hunt)
- Herschel Open Time Key Projects for nearby galaxies, including KINGFISH (Leslie Hunt, Stefano Zibetti), HeViCS (Simone Bianchi, Marco Bocchio, Edvige Corbelli, Sperello di Serego Alighieri, Carlo Giovanardi, Leslie Hunt, Laura Magrini, Stefano Zibetti), and DustPedia (Simone Bianchi, Viviana Casasola)
Research on COSMOLOGY and HIGH-REDSHIFT UNIVERSE
How cosmic structures formed and how galaxies were assembled remain key open questions in the study of modern cosmology. Theoretical models of primordial star formation and observations of samples faint high-redshift galaxies and clusters are the cornerstone of our group. By combining results from observational and theoretical research, the ultimate aim is to constrain the epoch of structure and galaxy formation, and broaden our understanding of physical processes at work in the early universe. Specifically, our group is engaged in studies of:
- Formation, evolution, and survival of dust grains in primordial objects, and comparison of theoretical predictions and observations (Simone Bianchi, Marco Bocchio)
- Early-type galaxy scaling relations at high redshift (Sperello di Serego Alighieri)
- Chemical evolution and mass-metallicity scaling relations over cosmic epochs (Giovanni Cresci, Anna Gallazzi, Filippo Mannucci, Alessandro Marconi, Guido Risaliti)
- Stellar populations, dynamics, morphology, and physical properties of distant galaxy populations (e.g., GEMS followup, LSD, SINS survey, LEGA-C ESO public spectrocopic survey) (Giovanni Cresci, Anna Gallazzi, Filippo Mannucci, Alessandro Marconi, Stefano Zibetti)
- Supernova rates and progenitor properties as a function of galaxy morphology and redshift (Filippo Mannucci)
- Clusters of galaxies at high redshift: structure formation and cosmology, thermodynamics of the Intra Cluster Medium and physics of cool cores (Paolo Tozzi)
- X-ray surveys of galaxy clusters (Paolo Tozzi)
- QSO absorption systems (Stefano Zibetti)
- Gamma-ray bursts, afterglows, and their host galaxies through the Consorzio Italiano per Burst Ottici (CIBO) (Leslie Hunt, Filippo Mannucci)
- Cosmic Polarization Rotation, an astrophysical test of fundamental physics (Sperello di Serego Alighieri)
- Quasars as cosmological tools: measurement of cosmological parameters and tests of the cosmological model through a Hubble diagram of quasars, built using the non-linear relation between UV and X-ray emission in quasars (Elisabeta Lusso, Guido Risaliti)
Guido Risaliti
Main research interests:
1) Structure and geometry of the circumnuclear medium of AGN, particularly through hard X-ray observations of obscured sources.
2) Spectral energy distribution of AGN, X-ray to optical correlations, bolometric corrections and contribution of AGN to the cosmic backgrounds
3) Physics of Ultraluminous Infrared Galaxies (ULIRGs): analysis of the AGN and