Orbit Tomography of Binary Supermassive Black Holes with Very Long Baseline Interferometry
01/12 2022 Seminar
- Title Orbit Tomography of Binary Supermassive Black Holes with Very Long Baseline Interferometry
- Speaker 方芸 (北京大学科维理天文与天体物理研究所)
- Date 2022年1月12日 15:00
- Venue 南楼6620
Supermassive black hole binaries (SMBHBs) could form as a consequence of galaxy mergers. The dynamical friction at the early stage brings the two SMBHs together to an order of parsecs separation and then forms a binary. At the sub-parsec separations, the SMBHBs emit gravitational waves efficiently at the pulsar timing array (PTA) band and make the SMBHBs merge within the Hubble timescale. There is still a debate over this “final parsec problem” about this separation gap. Observing SMBHBs at sub-parsec separations is sufficient to address this problem and also important for gravitational wave astrophysics at the PTA band. In this work, we study the possibility to infer the orbital parameters of a SMBHB by time-dependent measurements with Very Long Baseline Interferometry, such as the Event Horizon Telescope (EHT). Assuming a point-like luminosity image model, we show that with multiple years of observations by EHT, it is possible to recover the SMBHB orbital parameters from their time-varying visibilities even if the binaries orbital period is a few times longer than the duration of observation. Together with the future gravitational wave detections of resolved sources of SMBHBs with PTA, and/or the detections of optical-band light curves, we will be able to further measure the individual mass of the binary, and even determine the Hubble constant if the total mass of the binary is measured.