ALMAGAL. VII. Cataloging Hierarchical Continuum Structure from Cores to Clumps across the Galactic Disk

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Abstract Investigating the multiscale fragmentation of dense clumps into compact cores is essential for understanding the processes that govern the initial distribution of mass in stellar clusters and how high-mass stars (>8 M ⊙ ) form. We present a catalog of the hierarchical continuum structure from 904 clumps observed in the ALMAGAL program, a high-resolution (0 . ″ 15–0 . ″ 8) 1.38 mm Atacama Large Millimeter/submillimeter Array large program targeting dense clumps capable of high-mass star formation throughout the Galactic disk. We use astrodendro , a dendrogram-based algorithm, on a uniform linear resolution (2000 au) version of the data to extract 5160 continuum structures with effective radii spanning 800–42000 au and estimated masses between 0.05–670 M ⊙ . With our large sample, we statistically examine differences in clump properties for regions with varying levels of hierarchical complexity. We find that clumps exhibiting the richest hierarchical morphology have distributions with higher dust temperatures, surface densities, luminosity-to-mass ( L / M ) ratios, and most massive core masses, indicating that these regions tend to be at later evolutionary stages. We find a positive correlation between the mass of cores from the ALMAGAL core catalog and the surface density of their surrounding structures identified in this work. However, this correlation is weaker for cores in more evolved clumps, where lower-mass cores can be found at higher local surface densities. This could indicate that some cores accrete mass less efficiently from the intraclump reservoir than others, despite the total available mass increasing over time, a scenario that is congruent with a clump-fed core accretion model.

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