Oral Presentation
Dust, gas, and metals: Observing Dust Evolution in Nearby Galaxies
Presenter: I-Da Chiang (ASIAA)
The dust-to-metals mass ratio (D/M) measures the fraction of metals locked in solid grains in the interstellar medium. How D/M depends on the local environment, e.g. metallicity and gas density, provides keen insights into the evolution of interstellar dust. We measure the spatially resolved D/M at ~kpc scale in 5 nearby spirals. Our results show a roughly constant D/M at 12+log(O/H) ~ 8.2 to 8.8. Meanwhile, we confirm that the D/M is sensitive to how we derive the molecular gas content, i.e., the adopted CO-to-H2 conversion factor. We also notice that a constant CO-to-H2 conversion factor or a CO-to-H2 conversion factor modeled by metallicity only would result in decreasing D/M with increasing metallicity and gas density, which contradicts model expectations. On the other hand, a model that has a lower CO-to-H2 conversion factor in galaxy centers yields non-negative correlations between D/M and metallicity. We further push the resolved D/M measurements to a larger sample set, 49 nearby galaxies, and the results are qualitatively consistent.
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