2003MNRAS.344..461M

Recent observations indicate that some class 0 sources have accretion rates orders of magnitude higher than those of class I. We investigated the conditions for the high accretion rates of some class 0 sources by numerical calculations, modelling an external trigger. For no external trigger, we find that the maximum value of the accretion rate is determined by the ratio α of the gravitational energy to the thermal one within a flat inner region of the cloud core. The accretion rate reaches ∼10^–4 M_☉yr^–1 if the cloud core has α≳ 2. For an external trigger, we find that the maximum value of the accretion rate is proportional to the momentum given to the cloud core. The accretion rate reaches ≳10^–4 M_☉yr^–1 with a momentum of ∼0.1 M_☉km/s when the initial central density of the cloud core is ∼10^–18 g/cm³. A comparison between recent observational results for pre-stellar cores and our model with no triggered collapse indicates that the flat inner regions of typical pre-stellar cores are not large enough to cause accretion rates of ∼10^–4 M_☉yr^–1. Our results show that the triggered collapse of the cloud core is more preferable for the origin of the high accretion rates of class 0 sources than no triggered collapse.