Direct evidence of non-disk optical continuum emission around an active black hole

Abstract

Accretion onto black holes is key to their growth over cosmic time1, especially during the active galactic nuclei phase when the inflowing material forms a radiatively efficient accretion disk2. To probe the disk, indirect imaging methods such as reverberation mapping3–6 and microlensing7,8 are required. Recent findings suggest that the disk may be larger than theoretical predictions by a factor of a few4,6,9, thus casting doubt on our understanding of accretion in the general astrophysical context. Whether new physics is implied10–12 or poorly understood biases are in effect5,6,13,14 is a longstanding question. Here, we report new reverberation data based on a unique narrowband-imaging design15, and argue that time delays between adjacent optical bands are primarily associated with the reprocessing of light by a farther away under-appreciated non-disk component. This component is associated with high-density photoionized material that is uplifted from the outer accretion disk, probably by radiation-pressure force on dust, and thus may represent the long-sought origin of the broad-line region16. Our findings suggest that the optical phenomenology of some active galactic nuclei may be substantially affected by non-disk continuum emission with implications for measuring the fundamental properties of black holes and their active environs over cosmic time. New variability data of the accretion disk in active galactic nuclei argue for the existence of a farther away under-appreciated non-disk component associated with high-density photoionized material that is uplifted from the outer accretion disk.