Understanding disk-based dynamical mass measurements
Mass is the fundamental property that determines a star’s fate. Compared to the masses of their older cousins on the main sequence, however, the masses of young pre-main sequence stars are relatively uncertain. Fortunately, young stars have a unique advantage that we can exploit to precisely infer their mass: many often host a protoplanetary disk made of gas and dust, the site of future and ongoing planet formation. By modeling the rotation of this disk, we can dynamically “weigh” the host star(s). Circumstellar disks are typically mm-bright, which means that interferometers like the Atacama Large Millimeter Array (ALMA) and the Submillimeter Array (SMA) are ideal instruments for deriving stellar masses.
We put together a set of notes, here, explaining why and how we measure dynamical masses of stars. These notes are included as part of the DiskJockey project, which is a suite of tools written in the Julia programming language designed to forward-model radio interferometric observations.