Largest Black Holes in the Sky Origin and Evolution of Horizon-Scale Structures

• Applicant: Professor Dr. Andreas Eckart
• Subject Area: Astrophysics and Astronomy
• Term: from 2019 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 411720221

Extreme conditions develop in the cosmic environment by the interplay of strong gravitational and magnetic fields. This is particularly the case of the immediate vicinity of rapidly rotating black holes residing in nuclei of galaxies. We pro- pose to study processes of inflow/outflow interaction, tidal effects, and the frame dragging of General Relativity (GR) acting on accreting plasma and leading to transient shocks and the subsequent particle acceleration on spatial scales comparable with the event horizon and the corresponding dynamical time.Only now these processes become accessible observationally via high-angular resolution observational techniques and their interpretation requires theoretical exploration. The proposed collaboration project connects the prior experience of the Czech team (lead by V. Karas in Prague) in the field of GR relativistic astrophysics, especially in the context of radiation processes operating in gaseous accretion discs in strong gravity, and the lasting experience of the German team (lead by A. Eckart in Cologne) in observation, modelling and data interpretation for the Galactic Center supermassive black hole (SMBH).Within GR framework we will discuss astrophysical mechanisms that can accelerate particles and produce flares from SMBHs magnetized by external sources. Rapid rotation (spin) is an essential ingredient in our scenario. We will explore the dynamical properties of motion of accelerated material in the vicinity of magnetized SMBH, namely, the transition from regular to chaotic motion and the Recurrence Characteristics of chaos onset, including the role of SMBH spin. We will compare theoretical models to observations performed especially in millimeter and near-infrared spectral bands. We want to focus our attention on the region as close to the black hole as allowed by the available techniques.On the side of observations, we will model the observed variability and structural information available for two outstanding objects: Sagittarius A* (the inactive center of the Milky Way), and M87 (the nucleus of the nearby active giant elliptical galaxy). Along with the modelling we plan to carry out supplementary observations at infrared wavelengths in conjunction with radio and X-ray observations. We will concentrate on the regime accessible to Event Horizon Telescope Observations of SgrA* for which we take simultaneous NIR data. As a final goal we will discuss the structural features and variability properties within the rotating magnetized SMBH framework. Prospects for precision measurements of the physical parameters of supermassive black holes in these objects are now realistic, and most exciting. In a broad collaboration the joint Czech-German team plans to explore different approaches to the problem of accreting black holes.

• DFG Programme: Research Grants
• International Connection: Czech Republic
• Partner Organisation: Czech Science Foundation
• Cooperation Partner: Professor Vladimir Karas, Ph.D.