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Description
Planck Galactic Cold Clumps (PGCCs) are considered to be the ideal targets to probe the early phases of star formation. We have conducted a survey of 72 young dense cores inside PGCCs in the Orion complex with the Atacama Large Millimeter/submillimeter Array (ALMA) at 1.3mm (band 6) using three different configurations (resolutions ~0.35", 1.0", and 7.0") to statistically investigate their evolutionary stages and substructures. We have obtained images of the 1.3mm continuum and molecular line emission (^12^CO, and SiO) at an angular resolution of ~0.35" (~140au) with the combined arrays. We find 70 substructures within 48 detected dense cores with median dust mass ~0.093M_{sun}_ and deconvolved size ~0.27". Dense substructures are clearly detected within the central 1000au of four candidate prestellar cores. The sizes and masses of the substructures in continuum emission are found to be significantly reduced with protostellar evolution from Class 0 to Class I. We also study the evolutionary change in the outflow characteristics through the course of protostellar mass accretion. A total of 37 sources exhibit CO outflows, and 20 (>50%) show high-velocity jets in SiO. The CO velocity extents ({Delta}Vs) span from 4 to 110km/s with outflow cavity opening angle width at 400au ranging from [{Theta}_obs_]_400_~0.6"-3.9", which corresponds to 33.4{deg}-125.7{deg}. For the majority of the outflow sources, the {Delta}Vs show a positive correlation with [{Theta}_obs_]_400_, suggesting that as protostars undergo gravitational collapse, the cavity opening of a protostellar outflow widens and the protostars possibly generate more energetic outflows.
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