Assigned ID: 53 ----- Submission 1 (Thu Jan 20 01:06:51 GMT 2005) ----- The spectral energy distributions (SEDs) of AGNs encode valuable information on the physics of accretion onto black holes. Until very recently, however, data on SEDs for low-luminosity AGNs (LINERs and nearby Seyferts) have been sorely lacking. Initial studies based on small samples indicate that the SEDs of low-luminosity AGNs exhibit profound differences compared to those of their more luminous counterparts such as classical Seyferts and quasars. The most noticeable trait is the weakness of the "big blue bump," a feature normally attributed to thermal emission from a thin accretion disk. This unexpected but potentially very important result has led to suggestions that low-luminosity AGNs accrete via a fundamentally different mode, perhaps in a hot, radiatively inefficient flow. This proposition, if it can be confirmed, has important implications for our understanding of black hole accretion and for elucidating the physical properties of low-level nuclear activity, which is extremely common in nearby galaxies. We propose to significantly enlarge the current sample of SEDs for low-luminosity AGNs by combining existing high-resolution nuclear fluxes measured in the radio (VLA) and X-rays (Chandra) with new optical and near-infrared data points to be extracted from archival WFPC2, ACS, and NICMOS images. This project will increase the current sample of SEDs by more than an order of magnitude.

AGN/QUASARS 12 95000 false 0.0 false false false false false SUPPORTED