Research

Like normal galaxies, active galaxies are systems of stars, gases, and dust clouds bound to each other by self-gravitation. However, their nuclei contain "active" supermassive black holes that absorb gas from the surroundings and convert the gas's gravitational energy into intense radiation and (sometimes relativistic) outflows. We study the physics of active galactic nuclei (AGN) and supermassive black holes with the following particular approaches:

1. Directly image the matter and magnetic field distribution around the cosmic black holes on the event horizon scales (down to a few Schwarzschild radii) to understand how the mass inflow and outflow occur.
   
   

2. Analyze complex time-variable signals (both photons and particles such as neutrinos) from the black holes on short (<hour) and long (>decades) timescales to provide new models of energy generation and transfer mechanisms behind the variability.
   
   

3. Discover and investigate new types of active (and inactive) black holes in the nearby and early universe to reveal what physical conditions ultimately lead to the birth and death of an active black hole.

We use cutting-edge observing facilities worldwide, across all electromagnetic spectra from radio to gamma-rays, to observe the extreme objects in the universe.

In particular, we specialize in radio astronomical observations where the interferometric technique allows the combination of many separate antennas to form a large virtual telescope, whose size can be as big as Earth, to achieve an ultra-high angular resolution not be realized by any other method. This allows us to image regions close to the small black holes and rapidly time-variable emission zones, typically associated with cosmic high energy signals such as gamma rays, neutrinos, and gravitational waves. Also, global networks of telescopes observing variable and transient sources are essential to track the time evolution of flaring black hole objects.   

Therefore, we conduct active collaborative research with many international and domestic research organizations and researchers in Europe, the US, and Asia,  who are involved in global radio astronomical, VLBI, and space-based observations of cosmic black holes.