Mid-infrared Continuum of Starburst Nuclei: Contribution from Hot Large Grains within H α Regions?

摘要

The IRAS 12 and 25 fluxes are compared with the Br flux in a sample of starburst nuclei. Good correlations are found between them. The subsequent analysis indicates the presence of two components in the mid-infrared continuum: the nonthermal emission from "small grains" which are heated transiently by nonionizing photons outside the H II regions and the thermal emission from "large grains" which are heated to"140 K by ionizing, nonionizing, and Lyα photons inside the H II regions.