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

Accretion onto black holes is key to their growth over cosmic time ¹ , especially during the active galactic nuclei phase when the inflowing material forms a radiatively efficient accretion disk ² . To probe the disk, indirect imaging methods such as reverberation mapping ^3–6 and microlensing ^7,8 are required. Recent findings suggest that the disk may be larger than theoretical predictions by a factor of a few ^4,6,9 , thus casting doubt on our understanding of accretion in the general astrophysical context. Whether new physics is implied ^10–12 or poorly understood biases are in effect ^5,6,13,14 is a longstanding question. Here, we report new reverberation data based on a unique narrowband-imaging design ¹⁵ , 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 region ¹⁶ . 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.