Spitzer Observations of Low-Luminosity Isolated and Low Surface Brightness Galaxies

We examine the infrared properties of five low surface brightness galaxies (LSBGs) and compare them with related but higher surface brightness galaxies, using Spitzer Space Telescope images and spectra. All the LSBGs are detected in the 3.6 and 4.5 μm bands, representing the stellar population. All but one are detected at 5.8 and 8.0 μm, revealing emission from hot dust and aromatic molecules, although many are faint or pointlike at these wavelengths. Detections of LSBGs at the far-infrared wavelengths of 24, 70, and 160 μm are varied in morphology and brightness, with only two detections at 160 μm, resulting in highly varied spectral energy distributions. Consistent with previous expectations for these galaxies, we find that detectable dust components exist for only some LSBGs, with the strength of dust emission dependent on the existence of bright star-forming regions. However, the far-infrared emission may be relatively weak compared with normal star-forming galaxies.