Barnes, A. T.A. T.BarnesHenshaw, J. D.J. D.HenshawFONTANI, FRANCESCOFRANCESCOFONTANIPineda, J. E.J. E.PinedaCosentino, G.G.CosentinoTan, J. C.J. C.TanCaselli, P.P.CaselliJiménez-Serra, I.I.Jiménez-SerraLaw, C. Y.C. Y.LawAvison, A.A.AvisonBigiel, F.F.BigielFeng, S.S.FengKong, S.S.KongLongmore, S. N.S. N.LongmoreMoser, L.L.MoserParker, R. J.R. J.ParkerSánchez-Monge, Á.Á.Sánchez-MongeWang, K.K.Wang2025-02-142025-02-1420210035-8711http://hdl.handle.net/20.500.12386/35978Infrared dark clouds (IRDCs) are potential hosts of the elusive early phases of high mass star formation (HMSF). Here, we conduct an in-depth analysis of the fragmentation properties of a sample of 10 IRDCs, which have been highlighted as some of the best candidates to study HMSF within the Milky Way. To do so, we have obtained a set of large mosaics covering these IRDCs with Atacama Large Millimeter/submillimeter Array (ALMA) at Band 3 (or 3 mm). These observations have a high angular resolution (∼3 arcsec; ∼0.05 pc), and high continuum and spectral line sensitivity (∼0.15 mJy beam<SUP>-1</SUP> and ∼0.2 K per 0.1 km s<SUP>-1</SUP> channel at the N<SUB>2</SUB>H<SUP>+</SUP> (1 - 0) transition). From the dust continuum emission, we identify 96 cores ranging from low to high mass (M = 3.4-50.9 M<SUB>⊙</SUB>) that are gravitationally bound (α<SUB>vir</SUB> = 0.3-1.3) and which would require magnetic field strengths of B = 0.3-1.0 mG to be in virial equilibrium. We combine these results with a homogenized catalogue of literature cores to recover the hierarchical structure within these clouds over four orders of magnitude in spatial scale (0.01-10 pc). Using supplementary observations at an even higher angular resolution, we find that the smallest fragments (<0.02 pc) within this hierarchy do not currently have the mass and/or the density required to form high-mass stars. None the less, the new ALMA observations presented in this paper have facilitated the identification of 19 (6 quiescent and 13 star-forming) cores that retain >16 M<SUB>⊙</SUB> without further fragmentation. These high-mass cores contain trans-sonic non-thermal motions, are kinematically sub-virial, and require moderate magnetic field strengths for support against collapse. The identification of these potential sites of HMSF represents a key step in allowing us to test the predictions from high-mass star and cluster formation theories.STAMPAen10.1093/mnras/stab803https://academic.oup.com/mnras/article/503/3/4601/61798562021MNRAS.503.4601BFIS/05 - ASTRONOMIA E ASTROFISICA