With the Stratospheric Observatory for Infrared Astronomy ( SOFIA ) routinely operating science flights , we demonstrate that observations with the Faint Object infraRed CAmera for the SOFIA Telescope ( FORCAST ) can provide reliable estimates of the internal luminosities , L _ { int } , of protostars .
We have developed a technique to estimate L _ { int } using a pair of FORCAST filters : one “ short-wavelength ” filter centered within 19.7–25.3 \mu m , and one “ long-wavelength ” filter within 31.5–37.1 \mu m. These L _ { int } estimates are reliable to within 30–40 % for 67 % of protostars and to within a factor of 2.3–2.6 for 99 % of protostars .
The filter pair comprised of F 25.3 \mu m and F 37.1 \mu m achieves the best sensitivity and most constrained results .
We evaluate several assumptions that could lead to systematic uncertainties .
The OH5 dust opacity matches observational constraints for protostellar environments best , though not perfectly ; we find that any improved dust model will have a small impact of 5–10 % on the L _ { int } estimates .
For protostellar envelopes , the TSC84 model yields masses that are twice those of the Ulrich model , but we conclude this mass difference does not significantly impact results at the mid-infrared wavelengths probed by FORCAST .
Thus , FORCAST is a powerful instrument for luminosity studies targeting newly discovered protostars or suspected protostars lacking detections longward of 24 \mu m. Furthermore , with its dynamic range and greater angular resolution , FORCAST may be used to characterize protostars that were either saturated or merged with other sources in previous surveys using the Spitzer Space Telescope or Herschel Space Observatory .