Transient protostellar cores in high mass star forming regions revealed by time-resolved synthetic imaging of dust emission

ABSTRACT The connection between dense gas cores and their infant protostars is key to understanding how stars form in molecular clouds. In this paper we investigate the properties, persistence, and protostellar content of cores that would be identified by a dendrogram analysis of 1.3 mm ALMA images. We use a time series of synthetic images produced by post-processing a simulation of star formation in a massive globally collapsing clump, with polaris to calculate dust radiative transfer and casa to generate synthetic ALMA data. Identifying sinks in the simulation with protostars, we find that most dendrogram-identified cores do not contain any protostars, with many cores being transient features associated with clumpy flow along feeder filaments. Cores with protostars generally host $\le$3, and protostellar mass is not strongly correlated with the mass of the parent cores due to their transience and shifting boundaries. Calculating observationally relevant intensity-weighted average temperatures for all cores, we find that even at early times the core temperature distribution spans tens of Kelvin, and its width increases with time. The 1.3 mm peak and integrated intensity of the brightest mm core do not increase monotonically as the most massive associated protostar grows, indicating it cannot be assumed that brighter mm sources host more massive protostars. Leveraging the time domain, we test observational properties that have been proposed as potential evolutionary indicators and find that only the total 1.3 mm flux density of the region, the total 1.3 mm flux density in cores, and the number of cores show strong, statistically significant correlation with time.