This week's PhD colloquia are highlighted.
|11:15||Stellar radio beacons for Galactic astrometry|
Current radio campaigns are proving complementary astrometric data to Gaia particularly for the Galactic plane where the optical stellar emission is obscured by dust and gas. In this talk, I relate the synergies between Gaia and VLBI astrometry using maser stellar emission from young massive stars and evolved stars in the Galactic plane, which provide important clues on: intrinsic stellar properties, characterization of different stellar populations, the fundamental Galactic parameters and the distribution of the Galactic spiral structure.
|Luis Henry Quiroga Nunez||NRAO|
|11:15|| Dynamics of the Oort CLoud and the Formation of
Interstellar Comets||Santiago Torres||Leiden|
|17:00||Dark ice chemistry in interstellar clouds|
Near the beginning of solar-type star formation, a molecular cloud filled with dust and gas is formed. As the molecular hydrogen density rises past ~103 cm-3, external UV photons are increasingly blocked from entering the cloud and gas-phase temperatures drop to ~10 K. Under such conditions, atoms readily accrete onto cold dust grains to form molecules, as the sticking coefficient of almost all atoms and molecules on these grains is unity. Without any external source of heat or ‘energetic’ particles driving the chemistry, this type of ice chemistry in molecular clouds is noted as ‘dark’ or ‘non-energetic’, and is dominated by radical-induced processes. In this talk, I will overview recent experimental laboratory results, supported by quantum chemical calculations, on the solid-state formation of simple and complex organic molecules (COMs) that can be formed by ‘dark’ ice chemistry. Particularly COMs will be highlighted, as the formation of only simple molecules by ‘dark’ ice chemistry has been largely realized. All experiments presented here are performed in the ultrahigh vacuum setup, SURFace REaction SImulation Device3 (SURFRESIDE3), which is designed to study solid-state ‘dark’ ice chemistry. Astronomical observations of ices are also presented, and are strongly linked to the experimental efforts. The presented formation pathways and abundances of a variety of simple molecules and COMs under astrochemically relevant conditions can be incorporated into astrochemical models, which can then be used to aid in future observational surveys with facilities such as the James Webb Space Telescope (JWST) and the Atacama Large Millimeter/submillimeter Array (ALMA).