The Rosetta Stone project: a comparison between observations and simulations to investigate the star-formation mechanisms in massive star-forming regions.

It is still debated whether massive star formation either follows a core-fed or clump-fed model. In this poster I will present the first results of the Rosetta Stone project, which has been designed to discriminate between the two scenarios. This is done by identifying the mechanisms driving the fragmentation of the condensations at parsec scales, known as clumps, into the seeds of future (high-mass) stars at thousands of AU scales, called fragments. The strategy involves comparing observations and numerical simulations. As the first case of study, 13 clumps at various evolutionary stages selected in the SQUALO project, an ALMA 1.3mm and 3mm survey, have been taken as a reference. The physical properties of the fragments identified within the SQUALO images (including number, mass, and relative distance of the fragments) have been interpreted by comparing them with those of a statistically significant sample of radiative MHD simulations of massive clumps fragmentation. Different realizations of parameters have been explored in the simulations, including some values which are representative of the observed clump properties (such as clump mass and radius), as well as others that are not accessible from the available data (such as the clump initial Mach number and the mass to magnetic flux ratio). Various time steps and 3 projections in the sky have been analyzed, for a total of 580 maps.  A post-processing strategy has been developed to reproduce the features of the ALMA telescope observations, obtaining synthetic observations from simulated data. Evidences from the analysis of the fragmentation properties derived by the comparison of observations and simulations seem to favor a clump-fed star-formation model in which the fragments are not isolated from the environment. Young and massive clumps initially fragment under the influence of non-thermal motions. Then the fragments accrete mass from the parental clump, which itself acts as gas reservoir, and by merger events.