2018/08/31 by I-Da Chiang, I-Da 宜達 Chiang 江, Karin M. Sandstrom +4 · 1 citation
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Black-body radiation #Emissivity #Galaxies: Formation, Evolution, Phenomena #Galaxy #Mass ratio #Metallicity #Milky Way #Optical depth #Spectral energy distribution #astro-ph.GA
paper · pdf · doi:10.3847/1538-4357/aadc5f
29 pages, 18 figures; accepted by ApJ
openalex created_date 2018/08/31 · arxiv created 2018/09/28 · openalex publication_date 2018/09/28 · arxiv updated 2018/10/02 · openalex updated_date 2026/08/05
Abstract The dust-to-metals ratio describes the fraction of heavy elements contained in dust grains, and its variation provides key insights into the life cycle of dust. We measure the dust-to-metals ratio in M101, a nearby galaxy with a radial metallicity ( Z ) gradient spanning ∼1 dex. We fit the spectral energy distribution of dust from 100 to 500 μ m with five variants of the modified blackbody dust emission model in which we vary the temperature distribution and how emissivity depends on wavelength. Among them, the model with a single-temperature blackbody modified by a broken power-law emissivity gives the statistically best fit and physically most plausible results. Using these results, we show that the dust-to-gas ratio is proportional to . This implies that the dust-to-metals ratio is not constant in M101, but decreases as a function of radius, which is equivalent to a lower fraction of metals trapped in dust at low metallicity (large radius). The dust-to-metals ratio in M101 remains at or above what would be predicted by the minimum depletion level of metals observed in the Milky Way. Our current knowledge of the metallicity-dependent CO-to-H 2 conversion factor suggests that variations in the conversion factor cannot be responsible for the trends in dust-to-metals ratio we observe. This change of dust-to-metals ratio is significantly correlated with the mass fraction of molecular hydrogen, which suggests that the accretion of gas-phase metals onto existing dust grains could contribute to a variable dust-to-metals ratio.