ODISEA: Disk dust mass distributions

The nearby, young Ophiuchus star-forming region contains hundreds of protostars in a range of evolutionary states. Using the Atacama Large Millimeter Array to observe their millimeter continuum emission, we have measured masses of, or placed strong upper limits on, the dust content of 279 disks.

The masses follow a log-normal distribution with a clear trend of decreasing mass from less to more evolved protostellar infrared class. The (logarithmic) mean Class I disk mass, M=3.8M_{Earth}_, is about 5 times greater than the mean Class II disk mass, but the dispersion in each class is so high, {sigma}_logM_~0.8-1, that there is a large overlap between the two distributions. The disk mass distribution of flat-spectrum protostars lies in between Classes I and II.