Physics CRA Seminar - Professor Jong-Hak Woo

Physics CRA Seminar - Professor Jong-Hak Woo

Title 1: "10,000 solar mass black hole in NGC 4395 - primordial or no AGN feedback”

Title 2: “Limited impact of AGN outflows on star formation based on low-z AGN studies”


June 20, 2019 - 11:00am to 12:00pm


Boggs Building


1-44 Vizlab


Seoul National University

Content Images


I will present the reverberation-mapping study of the lowest-luminosity Seyfert 1 galaxy NGC 4395, based on the monitoring campaign in 2017 and 2018. The time delay of the Hα emission is measured as 83±14 min. Combining with the Hα velocity dispersion 426±1 km/s, black hole mass is determined as ∼10,000 Msun, which is the smallest reverberation mass, and comparable to the low mass end of heavy seed primordial black holes. Interestingly, NGC 4395 is consistent with the M-σ relation, when σ is constrained from the central region, indicating that the relation requires no hierarchical galaxy assembly or AGN feedback.


I will highlight some of the main results from a series of studies searching for observational signatures of AGN feedback using low-z AGNs. First, we find no direct evidence of SF quenching since the sSFR of strong outflow AGNs is comparable to that of SF galaxies. In contrast, non-outflow AGNs show much lower sSFR than SF galaxies. Second, our IFU study of z~0.1 AGNs shows that outflow is confined in a relatively small region, suggesting a limited impact of outflows. We typically detect a ring-like star-forming structure at the edge of the outflow, implying both negative and positive feedback for given objects. These results suggest no evidence of instantaneous feedback and the overall impact of AGN feedback seems rather limited in the present-day universe.