Abstract:

The infrared (IR) emission of galaxies comes primarily from three sources: stars, interstellar gas, and dust. The emission from stars peaks in the near-infrared (NIR: 1-3 microns). Emission from atoms and molecules in interstellar gas makes up only a few percent of the infrared output of galaxies. The primary source of the mid-infrared (MIR: 3-30 microns) and far-infrared (FIR: 30-1000 microns) radiation is thermal emission from dust grains heated by starlight. For this reason, galaxies look very different in the MIR and FIR images from their visual appearance that is shaped by distribution of stars in them. In this lecture, I will tell you what we can learn by observing the IR emission of galaxies.