SODA III. binary systems in L1641 and L1647

We combined these data (resolution of ~1.1") with the ESO-VISTA near-infrared survey of the Orion A cloud (resolution of ~0.7"). From this dataset, multiple-star systems were selected using an iterative inside-out search in projected separation (>=1000AU). We identify 61 binary systems, 3 triple systems, and 1 quadruple system.

The separation range is between 1000 and 104AU. The dust mass distributions inferred via the Kaplan-Meier estimator yield a median mass of 3.23_-0.4_^+0.6^M_{Earth}_ for primary disks and 3.88_-0.3+_^0.3^M_{Earth}_ for secondary disks. Combining our data with those available for the Lupus and Taurus disks, we identify a threshold separation of about 130AU, beyond which the previously observed positive correlation between millimeter flux (and hence dust mass) and projected separation is lost.

Recent theoretical models confirm that pre- and post-threshold systems are the result of different star formation processes, such as the fragmentation of gravitationally unstable circumstellar disks, the thermal fragmentation of infalling cores, or the turbulent fragmentation of molecular clouds. We can rule out the dependence on different SFRs: the cumulative mass distributions of multiples in SFRs of similar ages are statistically indistinguishable.

This result strengthens the hypothesis that there is a universal initial mass distribution for disks.