Systematic errors in dust mass determinations: Insights from laboratory opacity measurements

TL;DR

This study reveals that current dust mass estimates in galaxies are significantly overestimated due to inaccurate assumptions about dust opacity, with laboratory measurements indicating a potential overestimation factor of up to 20.

Contribution

The paper demonstrates how laboratory-based FIR/submm dust opacity measurements can lead to more accurate dust mass estimates, highlighting biases in previous models.

Findings

Dust masses are overestimated by factors of 2 to 20 using standard models.

Laboratory measurements show FIR opacities are higher and temperature-dependent.

Current models may significantly bias our understanding of dust content in galaxies.

Abstract

The thermal emission of dust is one of the most important tracers of the interstellar medium: multi-wavelength photometry in the far-infrared (FIR) and submillimeter (submm) can be fitted with a model, providing estimates of the dust mass. The fit results depend on the assumed value for FIR/submm opacity, which in most models - due to the scarcity, until recently, of experimental measurements - is extrapolated from shorter wavelengths. Lab measurements of dust analogues, however, show that FIR opacities are usually higher than the values used in models and depend on temperature, which suggests that dust mass estimates may be biased. To test the extent of this bias, we create multi-wavelength synthetic photometry for dusty galaxies at different temperatures and redshifts, using experimental results for FIR/submm dust opacity, then we fit the synthetic data using standard dust models. We find that the dust masses recovered by typical models are overestimated by a factor 2 to 20, depending on how the experimental opacities are treated. If the experimental dust samples are accurate analogues of interstellar dust, therefore, current dust masses are overestimated by up to a factor 20. The implications for our understanding of dust, both Galactic and at high redshift, are discussed.