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Paper: Spitzer Observations of Diffuse 8 μm Emission in Local Group and Nearby Dwarf Galaxies
Volume: 381, The Second Annual Spitzer Science Center Conference: Infrared Diagnostics of Galaxy Evolution
Page: 42
Authors: Jackson, D.C.; Skillman, E.D.; Lee, H.; Gehrz, R.D.; Woodward, C.E.; Polomski, E.
Abstract: We present Spitzer Space Telescope 4.5 and 8.0 μm imaging of 15 Local Group and nearby dwarf galaxies. We detect prominent diffuse 8 μm emission in four of the most luminous galaxies in the sample (IC 1613, IC 5152, NGC 55, and NGC 3109), very low surface brightness emission from four others (DDO 216, Sextans A, Sextans B, WLM), and no diffuse emission from the remaining objects. These systems all have evidence for old and intermediate age star formation, thus the lack of diffuse 8 μm emission cannot be attributed to young galaxy ages. Also, we find that blowouts are unlikely to explain the paucity of diffuse 8 μm emission, since high resolution imaging of the neutral gas in these objects show no evidence of this. We propose the lack of this emission in low-metallicity systems may be due to the destruction of dust grains by supernova shocks, assuming the timescale to regrow dust grains and PAH molecules is long compared to the destruction timescale. The most likely explanation for the observed weak diffuse 8 μm emission is at least partly due to a general absence of dust (including PAHs), in agreement with their low metallicities.
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