Estimating the Luminosities of Protostars with Limited Infrared Photometry

Abstract The luminosities of protostars provide one of the only indirect methods of measuring their masses and mass accretion rates in their earliest stages of evolution. Accurate measurements of protostellar luminosities traditionally requires assembling complete spectral energy distributions (SEDs) from the near-infrared through millimeter wavelengths. In this work, we use published evolutionary radiative transfer models of collapsing protostellar cores to evaluate the extent to which protostellar luminosities can be estimated from a limited number of infrared photometric measurements. We confirm previous results showing a tight correlation (in log-log space) between the luminosity of a protostar and its flux at 70 microns, although we demonstrate that these previous results yield luminosity estimates that are too low by factors of 2–3. We expand this work to additional wavelengths, finding that single wavelengths at 40 μm– 350 μm provide luminosity estimates with a 1σ uncertainty of a factor of 3 (0.477 dex of L⊙) or lower, with the uncertainty reduced to a factor of 2 (0.301 dex of L⊙) or lower at 70 μm– 160 μm. While the shorter wavelengths observed by JWST (0.6 – 27.9 μm) do not correlate as well with luminosity, we demonstrate that using a single photometric measurement in two different JWST filters simultaneously can result in luminosity estimates that are less uncertain than even the best estimates obtained using a single JWST filter. Using a single photometric measurement in three different JWST filters simultaneously can result in luminosity estimates that are comparable in accuracy to those obtained using single far-infrared photometric flux measurements.