Global Spectral Energy Distributions of the Large Magellanic Cloud with Interstellar Dust

Abstract

The effects of dust on infrared emission vary among galaxies of different morphological types. We investigated integrated spectral energy distributions in infrared and submillimeter emissions from the Large Magellanic Cloud based on the observations using the Herschel Space Observatory and near- to mid-infrared observations from the Spitzer Space Telescope. We also used IRAS and WMAP observations to constrain the SEDs. We explain the observations by using dust models with different grain size distributions in the interstellar medium of the LMC, noting that the LMC has undergone processes that are different from those in the Milky Way. We determined a spectral index and a normalization factor in the range of -3.5 to -3.45 with grain radii in the range of 1 nm-300 nm for the silicate grain and 2 nm-1 um for the graphite grain. The best fit to the observed SED was obtained with a spectral index of -3.47. The grain size distribution is described using a power law but with a break that is introduced below a_b, where a larger exponent is used. Changing graphite grain size distribution significantly changed the SED pattern within the observational uncertainties. Based on the SED fits to the observations from submillimeter wavelengths to the infrared radiation in the LMC using GRASIL (Silva et al. 1998), we obtained a reasonable set of parameter values in chemical and geometric space together with the grain size distributions of a modified MRN model with the LMC extinction curve.