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

Doron Chelouche, Francisco Pozo Nuñez, Shai Kaspi

Research output: Contribution to journalLetterpeer-review


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.

Original languageEnglish
Pages (from-to)251-257
Number of pages7
JournalNature Astronomy
Issue number3
StatePublished - 1 Mar 2019

Bibliographical note

Funding Information:
We thank D. Maoz for continuous support of the project at the Wise Observatory, and S. Niv for enabling the robotic use of the C18 telescope. This work was partly supported by grants 950/15 from the Israeli Science Foundation and 3555/14-1 from the Deutsche Forschungsgemeinschaft. Computations on the Hive computer cluster at the University of Haifa are partly supported by Israeli Science Foundation grant 2155/15.

Publisher Copyright:
© 2018, The Author(s), under exclusive licence to Springer Nature Limited.

ASJC Scopus subject areas

  • Astronomy and Astrophysics


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