Signature of the fragmentation of massive cluster forming clumps in the spatial distribution of dense cores revealed by ALMA

[MCFCs cluster-forming clumps]

Stars are born from the hierarchical fragmentation of molecular clouds. Most of them, and almost all high-mass stars (M > 8 Msun), which play a fundamental role in the galactic ecology, form in clustered systems. However, how these systems form is still under debate, as there is no agreement on how the process of fragmentation starts and proceeds, primarily in massive star-forming regions. Although recent years have witnessed considerable progress in the characterization of young embedded protostellar clusters thanks to infrared surveys, the same steps forward were not achieved for the earliest phases where protoclusters are composed of dense cores, the stellar precursors, due to the limited angular resolution and sensitivity of millimeter surveys. The ALMAGAL Large Program filled this gap by observing with ALMA at 1.4 mm and high angular resolution (~1000 au) more than 1000 massive clumps, potential sites of high-mass and cluster formation, in a wide variety of Galactic environments. In this talk, I will present the characterization of the spatial distribution of the population of dense cores identified in the ALMAGAL clumps. The large sample of clumps observed by ALMAGAL allows us for a quantitative and statistically robust analysis of the cluster of cores. Specifically, I will discuss where dense cores are located, what are their reciprocal separation, and how they are spatially distributed in the clump, which are all clues about the physical conditions of the fragmentation process. Finally, I will discuss how these properties vary over the early evolution of these systems, before the dispersal of the gas due to the stellar feedback. Our results indicate that, despite the wide diversity of observed fragmentation aspects, the distributions of dense cores are compatible with pure gravitational fragmentation without a contribution due to the turbulent support. Nonetheless, the wide observed variety requires future dedicated modeling with numerical simulations to reproduce the statistical properties of the observed distributions.

Brief CV of Dr. Eugenio Schisano:

He is a researcher at INAF-IAPS in Rome where he studies the initial phases of the star formation process, working within the framework of large infrared and millimeter surveys of the Galactic plane. He obtained his PhD at the University “Federico II” studying circumstellar disks around solar-type stars. He worked as a post-doc at IAPS-INAF and at IPAC-CalTech in the analysis of major surveys of the Galactic plane acquired with space telescopes (Spitzer, Herschel, WISE), focusing his research on the filamentary structure of dense material connected to star-forming regions. He also works with data from ground-based radio telescopes, both single-dish and interferometers at millimeter wavelengths, for the multi-frequency analysis of star-forming regions. He is an expert in the analysis of astronomical images, both continuum and spectral line, and in statistical analysis techniques on large datasets.