The relation between the Mass Accretion Rate and the Disk Mass in Class I Protostars

The evidence of a relation between the mass accretion rate and the disk mass is established for young, Class II pre-main sequence stars. This observational result opened an avenue to test theoretical models and constrain the initial conditions of the disk formation, fundamental in the understanding of the emergence of planetary systems. However, it is becoming clear that the planet formation starts even before the Class II stage, in disks around Class 0 and I protostars. We show for the first time evidence for a correlation between the mass accretion rate and the disk mass for a large sample of Class I young stars located in nearby (< 500 pc) star-forming regions. We fit our sample, finding that the Class I objects relation has a slope flatter than Class II stars, and have higher mass accretion rates and disk masses. The results are put in context of the disk evolution models.