Observational signatures of compact objects in active galactic nuclei

Events Calendar

 Time:  Tuesday, December 27, 2022, 09:00am
 Title:  Observational signatures of compact objects in active galactic nuclei
 Speaker:  Dr.Hiromichi Tagawa (Columbia Univ)
 Location:  Online via Zoom


The origin of stellar-mass black hole mergers discovered through gravitational waves is being widely debated. Mergers in the disks of active galactic nuclei (AGN) represent a promising source of origin. By modelling the evolution of compact objects in AGN disks, we found that several observational signatures in gravitational wave data are only explained by the AGN channel. Beyond gravitational waves, a unique signature of AGN-assisted mergers is electromagnetic emission from the accreting black holes. We showed that jets launched by accreting black holes in the AGN disk can be detected as peculiar transients by infrared, optical, and X-ray observatories for mergers in AGNs. We found that this emission mechanism can explain the possible associations between gravitational wave events and the optical transient ZTF19abanrhr and the proposed gamma-ray counterparts GW150914-GBM and LVT151012-GBM. I will further present a smoking gun signature of this model and introduce exciting scientific ideas for unveiling these systems.


Dr. Tagawa is a JSPS fellow at Columbia University. He has completed his Ph.D. degree in 2017 at the University of Tokyo under the supervision of Prof. Naoteru Gouda. After that he worked at Eotvos Lorand University with Prof. Bence Kocsis, and then he worked at Tohoku University. Currently he is working at Columbia University with Prof. Zoltan Haiman.

Dr. Tagawa is an expert on the fields of gravitational wave astrophysics, multi-messenger astronomy, hydrodynamics, and stellar dynamics. In Columbia University, he is recently working on the observability of electromagnetic emission from merging compact objects.

Host: Junjie Mao