Speaker
Description
The physical mechanisms behind the fragmentation of high-mass dense clumps into compact star-forming cores and the properties of these cores are fundamental topics that are heavily investigated in current astrophysical research. The ALMAGAL survey (Molinari et al. 2025, A&A, in press) provides the opportunity to study this process at an unprecedented level of detail and statistical significance, featuring high-angular resolution $1.38$ mm ALMA observations of $1013$ massive dense clumps at various Galactic locations. These clumps cover a wide range of distances ($\sim2-8$ kpc), masses ($\sim10^{2}-10^{4}\,\mathrm{M_{\odot}}$), surface densities ($0.1-10$ g $\mathrm{cm^{-2}}$), and evolutionary stages (luminosity over mass ratio indicator within $\sim0.05-450\,\mathrm{L_{\odot}/M_{\odot}}$).
In this contribution (based on Coletta et al. 2025, A&A, in press), I present the catalog of compact sources obtained with the CuTEx algorithm from continuum images of the full ALMAGAL clump sample combining ACA-$7$m and $12$m ALMA arrays, reaching a uniform high median spatial resolution of $\sim1400$ au (down to $\sim800$ au). In detail, I characterize and discuss the revealed fragmentation properties and the estimated physical parameters of the core population. The ALMAGAL compact source catalog includes $6348$ cores detected in $844$ clumps ($83\%$ of the total), with a number of cores per clump between $1$ and $49$ (median of $5$). The estimated core diameters are mostly within $\sim800-3000$ au (median of $1700$ au). Core temperatures were assigned based on the $L/M$ of the hosting clump; estimated core masses range from $0.002$ to $345\,\mathrm{M_{\odot}}$ (complete above $0.23\,\mathrm{M_{\odot}}$), and exhibit a good correlation with the core radii ($M\propto R^{2.6}$). Furthermore, I discuss the variation in the core mass function (CMF) with evolution as traced by the clump $L/M$, finding a clear, robust shift and change in slope among CMFs within subsamples at different stages. This important finding suggests that the CMF shape is not constant throughout the star formation process, but rather it builds (and flattens) with evolution, with higher core masses reached at later stages. Moreover, all cores within a clump appear to grow in mass on average with evolution, while a population of possibly newly formed lower-mass cores is present throughout. The number of cores increases with the core masses, at least until the most massive core reaches $\sim10\,\mathrm{M_{\odot}}$.
Such statistically robust results favor a clump-fed scenario for high-mass star formation, in which cores form as low-mass seeds, and then gain mass while further fragmentation occurs in the clump.
