Speaker
Description
In the study of the interstellar medium, the study of dust thermal emission in the far-infrared is a central tool. Fitting the dust spectral energy distribution (SED) provides key information on interstellar medium column density and temperature. Often, the model used for such fits will be a modified blackbody, i.e. a Planck function at the temperature of the dust, modulated by a dust opacity assumed to follow a power law: $F_\nu \sim B_\nu(T)\, \lambda^{-\beta}$.
However, SED fit results depend strongly on the model opacity, and the power law approximation is being challenged by both observational and experimental results. The opacity of dust materials, such as silicates and carbon, is temperature-dependent. Most notably, the value of the slope $\beta$ decreases as the material gets warmer. Additionally, $\beta$ is not always constant with wavelength. It is essential to understand how these findings change our interpretation of dust emission SEDs.
I present my team’s work to quantify the effect of temperature-dependent, non-power law opacity on SED fits. This effect has been identified for some time as a possible source of systematics, but has not yet been studied quantitatively. We use optical data on several candidate dust materials to model dust opacity as a function of wavelength and temperature, and we produce a grid of synthetic galaxy SEDs. By fitting these synthetic observations with a fixed-opacity model, we can then recover the bias in the fit results. We find that the dust masses recovered by the fit can be underestimated or overestimated depending on the target’s temperature, redshift, and choice of photometric bands.
Our findings on dust abundances have applications in several astrophysical scenarios, such as the early Universe and the environment around AGB stars.
| Participate the oral/poster presentation award competition | No |
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