The origin of dust in early-type galaxies and implications for accretion onto supermassive black holes

We have conducted an archival Spitzer study of 38 early-type galaxies in order to determine the origin of the dust in approximately half of this population. Our sample galaxies generally have good wavelength coverage from 3.6μm to 160μm, as well as visible-wavelength Hubble Space Telescope (HST) images. We use the Spitzer data to estimate dust masses, or establish upper limits, and find that all of the early-type galaxies with dust lanes in the HST data are detected in all of the Spitzer bands and have dust masses of ∼10 5–10 6.5 M , while galaxies without dust lanes are not detected at 70μm and 160μm and typically have