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We present mid-IR interferometric observations of 6 type 1 AGNs at multiplebaseline lengths of 27--130m, reaching high angular resolutions up tolambda/B~0.02 arcseconds. For two of the targets, we have simultaneous near-IRinterferometric measurements as well. The multiple baseline data directly probethe radial distribution of the material on sub-pc scales. Within our sample,which is small but spans over ~2.5 orders of magnitudes in the UV/opticalluminosity L of the central engine, the radial distribution clearly andsystematically changes with luminosity. First, we show that the brightnessdistribution at a given mid-IR wavelength seems to be rather well described bya power law, which makes a simple Gaussian or ring size estimation quiteinadequate. Here we instead use a half-light radius R_1/2 as a representativesize. We then find that the higher luminosity objects become more compact innormalized half-light radii R_1/2 /R_in in the mid-IR, where R_in is the dustsublimation radius empirically given by the L^1/2 fit of the near-IRreverberation radii. This means that, contrary to previous studies, thephysical mid-IR emission size (e.g. in pc) is not proportional to L^1/2, butincreases with L much more slowly, or in fact, nearly constant at 13 micron.Combining the size information with the total flux specta, we infer that theradial surface density distribution of the heated dust grains changes from asteep ~r^-1 structure in high luminosity objects to a shallower ~r^0 structurein those of lower luminosity. The inward dust temperature distribution does notseem to smoothly reach the sublimation temperature -- on the innermost scale of~R_in, a relatively low temperature core seems to co-exist with a slightlydistinct brightness concentration emitting roughly at the sublimationtemperature.

Mapping the radial structure of AGN tori