ALMA-IMF XI. Hot core candidates sample

We built a catalog of 76 hot core candidates with masses ranging from ~0.2M_{sun}_ to ~80M_{sun}_, of which 56 are new detections. A large majority of these objects, identified from methyl formate emission, are compact and rather circular, with deconvolved full width at half maximum (FWHM) sizes of ~2300 au on average. The central sources of two target fields show more extended, but still rather circular, methyl formate emission with deconvolved FWHM sizes of ~6700au and 13400au.

About 30% of our sample of methyl formate sources have core masses above 8M_{sun}_ and range in size from ~1000au to 13400au, which is in line with measurements of archetypical hot cores. The origin of the CH_3_OCHO emission toward the lower-mass cores may be explained as a mixture of contributions from shocks or may correspond to objects in a more evolved state (i.e., beyond the hot core stage). We find that the fraction of hot core candidates increases with the core mass, suggesting that the brightest dust cores are all in the hot core phase.

Our results suggest that most of these compact methyl formate sources are readily explained by simple symmetric models, while collective effects from radiative heating and shocks from compact protoclusters are needed to explain the observed extended CH_3_OCHO emission. The large fraction of hot core candidates toward the most massive cores suggests that they rapidly enter the hot core phase and that feedback effects from the forming protostar(s) impact their environment on short timescales.