What we do (or try to)
The Computational Astrochemistry Group is very multidisciplinary and moves from micro to macroscales. The main goal is to link the theoretical and computational aspects of chemistry and astrophysics, ranging from the small-scale effects in quantum systems to the application of the microphysics on large-scales. We provide state-of- the-art models that allow a comparison and a better interpretation of the observational data, employing them to perform 3D hydrodynamical simulations of different environments. The main research interests are: astrochemistry; computational astrophysics; chemistry of low-metallicity star-forming regions, metal-poor stars, chemistry of the interstellar medium, and galaxy formation and evolution. We further work on the development and improvements of astrochemical networks, with particular emphasis on computational methods for networks reduction and chemical kinetics.
An important step towards the understanding of the star formation process is identifying the initial phases of the collapse, and deuteration is the best proxy for this purpose. This requires to build accurate networks including spin-state chemistry and isomers to be employed in hydrodynamical simulations of magnetized and turbulent collapsing filaments and cloud cores. We work on the development of reliable chemical models to accurately follow the effect of freeze-out, H2 ortho-to-para ratio, and cosmic-rays on the deuterium fractionation to explore its role as chemical clock of such environments. Post-processes of hydrodynamical simulations are used to compare with observational data.
The explosion of primordial stars enriched the medium by metals and dust which regulate the formation of the second generation of stars. Investigating how these were formed it is fundamental also to probe the primordial environment where the first generation of stars were born. A crucial role in the transition between the first and the second generation of stars has been played by dust, and in particular by its capacity to cool the gas efficiently down to the CMB temperature. This induces fragmentation and determine the fate and the masses of the second generation of stars. An interesting case is the Caffau stars, a very metal poor low-mass star, which shold have been formed via dust-induced fragmentation. We explore the macro and microphysics of metal-poor halos out of which these stars were formed, through hydrodynamical cosmological simulations.
We explore here the chemistry of the ISM in galaxies, both at solar metallicity as well as in metal-poor environments. We focus on the role of CII and on the H2 chemistry. CII is known to be one of the most important coolant in the interstellar medium, and it is considered a powerful tracer for the star formation activity. In addition, it can provide useful insights on the reionization epoch. Cosmological hydrodynamical simulations of galaxies at different metallicities and redshifts, including a proper chemical model which can follow the [CII] evolution, are very important to probe the correlation between [CII] and the star formation rate, and to follow the transition between the different phases of the ISM. The star formation process in metal-poor galaxies and how this correlates with the molecular gas is not yet fully understood. ALMA observations have reported a very inefficient star formation process in this kind of galaxies. It is then very important to perform galaxy simulations which are able to follow the evolution of the molecular gas for different dust grains compositions/distributions, and compare the results with recent observations.
KROME is a package which aims to provide microphysics and chemical networks to be included in hydrodynamical simulations of astrophysical objects.
In astrochemistry it is very important to find reliable tracers to determine the physical/chemical conditions in molecular clouds and star-forming regions as H2 cannot be directly observed in cold environments. The HF molecule has been recently considered as a very good tracer for different phases of the ISM for its peculiar chemical kinetics and has been observed in diffuse and molecular clouds. Nevertheless there are many uncertainties in the basic network of reactions which lead to its formation, and on its depletion on icy dust grains. We plan to improve our knowledge of the basic network of reactions involving HF and CF+ and employ this to perform hydrodynamical simulations of colliding flows (following the formation of molecular clouds) to probe the correlation of HF with the atomic and the molecular gas.
Within this project we are trying to build a 1D chemo-thermal model to study the atmosphere of an exomoon belonging to a free-floating planet. We make use of our private code PATMO.