Speaker
Description
The dust-to-metals ratio provides insights into the life cycle of dust. We measure the dust-to-metals ratio in M101, a nearby galaxy with a radial metallicity gradient spanning $\sim 1~\mbox{dex}$. We fit the dust spectral energy distribution (SED) from $100$ to $500~\mu m$ with five variants of the modified blackbody (MBB) dust emission model (free $\beta$, fixed $\beta$, broken emissivity, warm dust component, and a power-law radiation field distribution). The broken emissivity method performs the best among them, showing small residuals, reasonable $\tilde{\chi}^2$ distribution, a temperature gradient decreasing with radius and no violation of the upper bounds on available metals. We show that the dust-to-metals ratio is not constant in M101, but decreases as a function of radius, leading to a lower fraction of the heavy elements being trapped in dust at low metallicity. We show that the dust-to-gas ratio (DGR) is proportional to $Z^{1.71}$. Alternatively, we could instead explain the DGR gradient as an increase in emissivity as dust grains coagulate. If we assume the Draine et al. 2014 dust-to-metals relation, the opacity constant $\kappa_{160}$ would increase at most by a factor of two, which is similar to what Planck Collaboration et al. 2014 found.
| Consider for a poster? | Yes |
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