Distribution of Serpens South protostars

Recent millimeter-wavelength interferometry observations can now uncover faint and/or compact sources in order to study a more complete population of protostars, especially in nearby (D<500pc) clusters. Here we present ALMA observations of 1mm (Band 6) continuum in a 3x2-arcminutes region at the center of Serpens South. Our angular resolution of 1-arcsec is equivalent to 400 au, corresponding to scales of envelopes and/or disks of protostellar sources.

We detect 52 sources with 1mm continuum, and we measure masses of 0.002-0.9 solar masses corresponding to gas and dust in the disk and/or envelope of the protostellar system. For the deeply embedded (youngest) sources with no IR counterparts, we find evidence of mass segregation and clustering according to: the Minimum Spanning Tree method, distribution of projected separations between unique sources, and concentration of higher-mass sources near to the dense gas at the cluster center.

The mass segregation of the mm sources is likely primordial rather than dynamical given the young age of this cluster, compared with segregation time. This is the first case to show this for mm sources in a low-mass protostellar cluster environment.