Astro2020 Science White Paper: Measuring Protostar Masses: The Key to
  Protostellar Evolution
  Knowledge of protostellar evolution has been revolutionized with the advent
of surveys at near-infrared to submillimeter wavelengths. This has enabled the
bolometric luminosities and bolometric temperatures (traditional protostellar
evolution diagnostics) to be measured for large numbers of protostars. However,
further progress is difficult without knowing the masses of the central
protostars. Protostar masses can be most accurately determined via molecular
line kinematics from millimeter interferometers (i.e., ALMA). Theoretical
investigations have predicted the protostellar mass function (PMF) for various
protostellar mass accretion models, and it is now imperative to observationally
constrain its functional form. While ALMA has enabled protostellar mass
measurements, samples approaching 100 sources are necessary to constrain the
functional form of the PMF, and upgrades to ALMA and/or a new mm/cm facility
will increase the feasibility of measuring such a large number of protostar
masses. The masses of protostars will enable their stellar structure (radius
and intrinsic luminosity), evolution, and accretion histories to be better
understood. This is made more robust when effective temperatures and accretion
rates can be measured via ground/space-based near to mid-infrared spectroscopy.
Furthermore, access to supercomputing facilities is essential to fit the
protostar masses via radiative transfer modeling and updated
theoretical/numerical modeling of stellar structure may also be required.
