NGC 1068 SPHERE-VLT images

However, the derived stellar density is found to follow a r^-4^ cusp, which is much steeper than any other cusp, either theoretically predicted around a massive black hole, or observed in the centre of early- and late-type galaxies or in mergers. Introducing a segregation in the stellar population with a central excess of giant stars leads to a somewhat less steep exponent; however, the de-reddened luminosity of the stellar cusp, as well as the mass of dust and gas all appear much too high to be realistic.

An alternative scenario, where the Ks-band profile is well fitted by a combination of radiation from a stellar cusp identical to the H-band profile and thermal emission ofwarm/hot dust heated by the central engine appears much more satisfactory. NGC 1068 is shown to satisfy a relationship between half-light radius, cusp luminosity, and exponent that we established using a sample of luminous infrared galaxies (LIRGs) and ultraluminous infrared galaxies ULIRGs.

This suggests that the cusp is the remnant of a recent starburst. We identify the central point-like source with the very hot dust at the internal wall of the putative torus and derive an intrinsic luminosity that requires a central extinction A_K_~8, a value consistent with predictions by several torus models. The overall picture revealed by this study is closely consistent with the scheme of a central rather steep stellar cusp, embedded in a diluted medium of warm dust, while a compact and dense structure identified with the putative torus is required to interpret a highly reddened point-like central source of very hot dust.