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With mid-IR and near-IR long-baseline interferometers, we are now mapping theradial distribution of the dusty accreting material in AGNs at sub-pc scales.We currently focus on Type 1 AGNs, where the innermost region is unobscured andits intrinsic structure can be studied directly. As a first systematic study ofType 1s, we obtained mid-/near-IR data for small samples over ~3-4 orders ofmagnitudes in UV luminosity L of the central engine. Here we effectively tracethe structure by observing dust grains that are radiatively heated by thecentral engine. Consistent with a naive expectation for such dust grains, thedust sublimation radius R_in is in fact empirically known to be scaling withL^1/2 from the near-IR reverberation measurements, and this is also supportedby our near-IR interferometry. Utilizing this empirical relationship, wenormalize the radial extent by R_in and eliminate the simple L^1/2 scaling fora direct comparison over the samples. We then find that, in the mid-IR, theoverall size in units of R_in seems to become more compact in higher luminositysources. More specifically, the mid-IR brightness distribution is rather welldescribed by a power-law, and this power-law becomes steeper in higherluminosity objects. The near-IR flux does not seem to be a simple inwardextrapolation of the mid-IR power-law component toward shorter wavelengths, butit rather comes from a little distinct brightness concentration at the innerrim region of the dust distribution. Its structure is not well constrained yet,but there is tentative evidence that this inner near-IR-emitting structure hasa steeper radial distribution in jet-launching objects. All these should bescrutinized with further observations.

Probing the innermost dusty structure in AGN with mid-IR and near-IR interferometers