Chemical and physical processes in the earliest phases of star formation
The initial conditions in the process of star and planet formation are to be found in pre-stellar cores, which are dense (n_H > 10^5 cm-3), cold (T < 10 K), centrally concentrated and gravitationally contracting regions embedded in molecular clouds. Knowledge of the physical structure and kinematics of pre-stellar cores is needed to put constraints on theories of star and planet formation. This requires a good understanding of the pre-stellar core chemical structure, as spectral line profiles of trace species provide the only diagnostics of the dynamics leading to star and planet formation. Because of their simple structure and quiescent nature, pre-stellar cores are also ideal laboratories in which to measure key astrophysical processes and parameters. I will review work on pre-stellar cores in low-mass star-forming regions, showing Herschel observations and how ALMA will unveil the still unexplored central few hundreds AU of pre-stellar cores, the future stellar system cradles. I'll then move to high-mass star-forming regions and show that our work on nearby pre-stellar cores has provided a way to unveil massive starless cores and test star formation theories. Cycle 0 ALMA and OT2 Herschel data will be presented. Finally, I will show simulations of ALMA observations of a protoplanetary disk in the earliest stages of its evolution.