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We present 500 and 700 au resolution 1 and 3 mm Atacama Large Millimeter/submillimeter Array observations, respectively, of protostellar cores in protoclusters Sagittarius B2 (Sgr B2) North (N) and Main (M), parts of the most actively star-forming cloud in our Galaxy. Previous lower-resolution (5000 au) 3 mm observations of this region detected ∼150 sources inferred to be young stellar objects (YSOs) with M > 8 M ⊙. With a 10-fold increase in resolution, we detect 371 sources at 3 mm and 218 sources in the smaller field of view at 1 mm. The sources seen at low resolution are observed to fragment into an average of two objects. About one-third of the observed sources fragment. Most of the sources we report are marginally resolved and are at least partially optically thick. We determine that the observed sources are most consistent with Stage 0/I YSOs, i.e., rotationally supported disks with an active protostar and an envelope, that are warmer than those observed in the solar neighborhood. We report source-counting-based inferred stellar mass and the star formation rate of the cloud: 2800 M ⊙ and 0.0038 M ⊙ yr−1 for Sgr B2 N and 6900 M ⊙ and 0.0093 M ⊙ yr−1 for Sgr B2 M, respectively. [ABSTRACT FROM AUTHOR]

We studied the unique kinematic properties in massive filament G352.63-1.07 at 103 au spatial scale with the dense molecular tracers observed with the Atacama Large Millimeter/submillimeter Array. We find the central massive core M1 (12 M ⊙) being separated from the surrounding filament with a velocity difference of v − v ¯ sys = − 2 km s − 1 and a transverse separation within 3″. Meanwhile, as shown in multiple dense-gas tracers, M1 has a spatial extension closely aligned with the main filament and is connected to the filament toward both its ends. M1 thus represents a very beginning state for a massive, young star-forming core escaping from the parental filament, within a timescale of ∼4000 yr. Based on its kinetic energy (3.5 × 1044 erg), the core escape is unlikely solely due to the original filament motion or magnetic field but requires more energetic events such as a rapid intense anisotropic collapse. The released energy also seems to noticeably increase the environmental turbulence. This may help the filament to become stabilized again. [ABSTRACT FROM AUTHOR]