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Archeology of interstellar archipelagos: Reconstructing the lifecycle of star-forming clouds

Sede A. Riccò Via Santa Sofia 78, Catania

Determining how star-forming molecular clouds (MCs) arise from and interact with the diffuse interstellar medium (ISM) is crucial for understanding the initial conditions of planet and star formation and the evolution of the Milky Way and other similar galaxies. I will present state-of-the-art observations of neutral atomic hydrogen (HI) and interstellar magnetic fields, which, combined with numerical simulations and novel statistical tools based on machine vision, reveal three crucial aspects of the MC lifecycle. First, the signature of magnetization in the structure of MCs in the solar neighborhood, within 500 parsecs from the Sun. Two, the imprint of supernova feedback in the HI structure across the Galactic plane. And finally, the coupling between atomic and molecular gas in and around MCs. I will discuss the consequences of these findings for our understanding of the Galactic ecosystem and the prospects for radio-interferometric and submillimeter polarization observations from the forthcoming facilities.

Unraveling Space Weathering on Planetary and Astrophysical Surfaces

Sede A. Riccò Via Santa Sofia 78, Catania

It is well known that the interaction of energetic ions, electrons and photons with surfaces and interfaces leads to non-thermal desorption via a process typically referred to as desorption induced by electronic transitions (DIET).  When DIET involves either electrons or photons, these processes are generally referred to as electron-stimulated desorption and photon-stimulated desorption (PSD), respectively.  Recent attention has focused on understanding the role of non-thermal “space weathering” in the processing of interstellar grains and ices.
Specifically, there is deep interest in understanding the radiation processing of carbon grains in the solar nebula and unraveling the H2O formation mechanisms in solar nebula and planetary systems, including the Moon. Using graphite grains, the VUV photon-simulated oxidation of carbon grains via reactive scattering of water fragments produced by dissociative electron attachment at the buried interface was examined. The results suggested that VUV PSD at the buried water:carbon grain interface may help control the carbon inventory during planet formation. The inverse process, (i.e, the formation of water) may happen on metal-oxide samples such as mineral grains and lunar regolith samples, that contain or are terminated by hydroxyl groups. Solar wind space weathering experiments of several Apollo lunar samples demonstrated that thermally activated recombinative desorption (RD) can be H2O sources and that electron-stimulated reactive scattering to produce water may also be occurring, especially when the Moon is in the magnetopause.  RD can occur on a diurnal basis on the Moon and is prevalent during meteoroid impacts. The latter is simulated by laser irradiation studies followed by state and velocity resolved detection of the produced water.  Finally, evidence of space weathering and surface alteration has also been revealed using spatially resolved, high-resolution nanoscale Fourier transform infrared imaging/spectroscopy correlated with photoluminescence (PL) on Apollo samples with different origins and history.