BASS XXXII: Studying the Nuclear Millimeter-wave Continuum Emission of AGNs with ALMA at Scales ≲100-200 pc

Taiki Kawamuro*, Claudio Ricci, Masatoshi Imanishi, Richard F. Mushotzky, Takuma Izumi, Federica Ricci, Franz E. Bauer, Michael J. Koss, Benny Trakhtenbrot, Kohei Ichikawa, Alejandra F. Rojas, Krista Lynne Smith, Taro Shimizu, Kyuseok Oh, Jakob S. den Brok, Shunsuke Baba, Mislav Baloković, Chin Shin Chang, Darshan Kakkad, Ryan W. PfeifleGeorge C. Privon, Matthew J. Temple, Yoshihiro Ueda, Fiona Harrison, Meredith C. Powell, Daniel Stern, Meg Urry, David B. Sanders

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


To understand the origin of nuclear (≲100 pc) millimeter-wave (mm-wave) continuum emission in active galactic nuclei (AGNs), we systematically analyzed subarcsecond resolution Band-6 (211-275 GHz) Atacama Large Millimeter/submillimeter Array data of 98 nearby AGNs (z < 0.05) from the 70 month Swift/BAT catalog. The sample, almost unbiased for obscured systems, provides the largest number of AGNs to date with high mm-wave spatial resolution sampling (∼1-200 pc), and spans broad ranges of 14-150 keV luminosity { 40 < log [ L 14 − 150 / ( erg s − 1 ) ] < 45 }, black hole mass [ 5 < log ( M BH / M ⊙ ) < 10 ], and Eddington ratio ( − 4 < log λ Edd < 2 ). We find a significant correlation between 1.3 mm (230 GHz) and 14-150 keV luminosities. Its scatter is ≈0.36 dex, and the mm-wave emission may serve as a good proxy of the AGN luminosity, free of dust extinction up to NH ∼ 1026 cm−2. While the mm-wave emission could be self-absorbed synchrotron radiation around the X-ray corona according to past works, we also discuss different possible origins of the mm-wave emission: AGN-related dust emission, outflow-driven shocks, and a small-scale (<200 pc) jet. The dust emission is unlikely to be dominant, as the mm-wave slope is generally flatter than expected. Also, due to no increase in the mm-wave luminosity with the Eddington ratio, a radiation-driven outflow model is possibly not the common mechanism. Furthermore, we find independence of the mm-wave luminosity on indicators of the inclination angle from the polar axis of the nuclear structure, which is inconsistent with a jet model whose luminosity depends only on the angle.

Original languageEnglish
Article number87
JournalAstrophysical Journal
Issue number1
StatePublished - 1 Oct 2022


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