EPoS Contribution

Probing Star-Formation Mechanisms in Massive Star-Forming Regions: Bridging Observations and Simulations through the Rosetta Stone Project Alice Nucara INAF - IAPS, Rome, IT
The scenario behind the formation of the most massive stars remains a topic of debate. Here I will present the first results of the Rosetta Stone project, which has been designed to probe the star-formation mechanisms in massive star-forming regions by combining observations and dedicated numerical simulations. The project specifically targets the mechanisms driving the fragmentation of the compact structures at parsec scales, commonly referred to as clumps, into the seeds of future (high-mass) stars at thousands of AU scales, here referred to as fragments. As first case of study, a sample of 13 massive clumps at various evolutionary stages selected from the SQUALO project, an ALMA 1.3mm and 3mm survey, has been taken as a reference. The physical properties of the fragments identified within the SQUALO data (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 values which are representative of the observed clump properties (such as clump mass - M=500,1000M_☉ - and radius - R=0.4,0.8pc), as well as others that are not accessible from the available data (such as the clump initial Mach number - ℳ=7,10 - and the mass to magnetic flux ratio - μ=10,100). For each realization with a given set of parameters we have analyzed a minimum of 7 time-steps and explored the outcomes across 3 different projections, to account for the potential projection bias. We have also addressed stochastic fluctuations due to the initial seed by exploring two different seeds. We have therefore analyzed a total of 330 different maps. A post-processing strategy has been developed to reproduce the features of the ALMA observations, obtaining realistic synthetic observations from simulated data mimicking the properties of the SQUALO dataset. Source extraction has then been performed by means of the Hyper software, tuned to be consistent with the methods used in the analysis of the real data. Evidence from the analysis of the fragmentation properties of the clumps, 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 throughout all the explored evolutionary stages. Young and massive clumps initially fragment influenced by non-thermal contributions. Then the fragments accrete mass from the parental clump, which itself acts as gas reservoir. Furthermore, new seeds of star formation are observed to spawn along the evolution of the clumps.

Caption: 1.3mm continuum synthetic observations illustrating two snapshots of massive clumps fragmentation at sink formation efficiency (SFE) ∼5%. Exploration of the impact of the mass-to-flux ratio parameter, μ=10 (left) vs. μ=100 (right), on the fragmentation properties of a 1000M_☉ clump under identical initial conditions of Seed=1, R=0.4pc, and ℳ=10. Magenta stars are the centroids of the 4 and 8 fragments identified with Hyper.
Collaborators: A. Traficante, INAF-IAPS, IT S. Molinari, INAF-IAPS, IT P. Hennebelle, CEA, FR U. Lebreuilly, CEA, FR D. T. Ngo, CEA, FR	Relevant topic(s): Accretion Fragmentation High-Mass SF
Relevant Big Question: How can we enhance our understanding of star-formation mechanisms in massive star-forming regions by bridging observations and numerical simulations?