Can we trust the dust? The effect of temperature-dependent material opacity on determining interstellar dust masses

Lapo Fanciullo^1*, Jonathan Marshall², Francisca Kemper³

¹Department of Physics, Tamkang University, Taipei, Taiwan
²Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, Taiwan
³Institute of Space Sciences, Autonomous University of Barcelona, Barcelona, Spain

* Presenter:Lapo Fanciullo, email:lfanciullo.astro@gmail.com

Interstellar dust is an important tracer in several fields of study in astrophysics, such as star formation and galactic chemical evolution. To measure interstellar dust masses, a common method is to fit the spectral energy distribution (SED) of far-infrared thermal dust emission. A typical model used for this endeavor is a modified blackbody. However, these fit results depend on the adopted value for dust opacity. Recent experimental findings suggest that traditional dust opacity estimates may be systematically biased; in particular, dust opacity increases with material temperature. How does this new information change our dust mass estimates?
We quantify for the first time the effect of temperature-dependent dust opacity on SED fits. Using experimental data for candidate dust materials, we model dust opacity as a function of wavelength and temperature. We then produce a grid of synthetic galaxy SEDs, which we fit with a fixed-opacity model. We find a bias in fit results that depends on the target’s temperature, redshift, and available photometric bands. In particular, we find that dust mass at a redshift z = 8 can be overestimated by 25 to 60% compared to the same mass in the local Universe, with important consequences for cosmological evolution models.

Keywords: Astrophysics, Interstellar Medium, Interstellar Dust, Galaxies