The Properties of the Mid‐ to Far‐Infrared Emission in the Large Magellanic Cloud

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We investigate the properties of mid- to far-infrared emission in the Large Magellanic Cloud (LMC) based on the COBE DIRBE and IRAS Sky Survey Atlas data sets. We focus on the properties of far-infrared (FIR) thermal emission carried by submicron dust and mid-infrared (MIR) excess emission by very small grains in the LMC in comparison to those in the Milky Way. We carefully estimate the dust temperature by decomposing the various structures including young star clusters, supergiant shells, and CO molecular clouds and examine the MIR to FIR spectral energy distribution (SED) associated with each structure in the LMC. The amount of the MIR excess emission in 12 and 25 ?m relative to the total FIR emission (FFIR) in the LMC is generally smaller than that in the Milky Way, which confirms the scarcity of very small grains suggested by past studies on the extinction curve. The characteristics of 25 and 60 ?m excess emission proportional to the square of the incident radiation field strength appear around young star clusters in the LMC. This sequence can be reproduced by the superposition of dust emission under different radiation field strengths ranging from 1 to 105 times of that in the solar vicinity. Finally, the MIR to FIR SEDs in CO molecular clouds in the LMC are discussed. Through these attempts, we succeed in completely explaining the characteristics of mid- to far-infrared SEDs given by the infrared broadband photometric data sets in terms of the superposition of the standard stochastic heating dust model.