2017/06/14 by M. S. Oey, J. López-Hernández, J. Lopez-Hernandez +11 · 7 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Brightness #Cosmic dust #Galaxies: Formation, Evolution, Phenomena #Galaxy #Interstellar medium #Ionization #Large Magellanic Cloud #Optical depth #Radiative transfer #Surface brightness #astro-ph.GA
paper · pdf · doi:10.3847/1538-4357/aa73d3
published in The Astrophysical Journal 844(1), 63 (IOP Publishing) · Accepted to ApJ, May 15, 2017. 10 pages, 9 figures
arxiv created 2017/06/14 · openalex created_date 2017/06/23 · openalex publication_date 2017/07/20 · arxiv updated 2017/08/02 · openalex updated_date 2026/08/06
Abstract We use the Spitzer Surveying the Agents of Galaxy Evolution (SAGE) survey of the Magellanic Clouds to evaluate the relationship between the 8 μ m polycyclic aromatic hydrocarbon (PAH) emission, 24 μ m hot dust emission, and H ii region radiative transfer. We confirm that in the higher-metallicity Large Magellanic Cloud, PAH destruction is sensitive to optically thin conditions in the nebular Lyman continuum: objects identified as optically thin candidates based on nebular ionization structure show six times lower median 8 μ m surface brightness (0.18 mJy arcsec −2 ) than their optically thick counterparts (1.2 mJy arcsec −2 ). The 24 μ m surface brightness also shows a factor of three offset between the two classes of objects (0.13 versus 0.44 mJy arcsec −2 , respectively), which is driven by the association between the very small dust grains and higher density gas found at higher nebular optical depths. In contrast, PAH and dust formation in the low-metallicity Small Magellanic Cloud is strongly inhibited such that we find no variation in either 8 μ m or 24 μ m emission between our optically thick and thin samples. This is attributable to extremely low PAH and dust production together with high, corrosive UV photon fluxes in this low-metallicity environment. The dust mass surface densities and gas-to-dust ratios determined from dust maps using Herschel HERITAGE survey data support this interpretation.