Testing General Relativity with Accretion-Flow Imaging of Sgr A^{*}

Area of Science:

• Astrophysical black holes
• Strong gravity physics
• General relativity

Background:

• The Kerr metric is the theoretical description of rotating black holes.
• Astrophysical black holes are potential sources of deviations from the Kerr metric.
• The Event Horizon Telescope (EHT) is a global very long baseline interferometer.

Purpose of the Study:

• To constrain quadrupolar deviations of Sagittarius A* from the Kerr metric.
• To simulate future observational constraints with an expanded EHT array.
• To assess the potential for high-precision strong gravity measurements.

Main Methods:

• Utilizing a radiatively inefficient accretion flow model.
• Analyzing data within a quasi-Kerr background.
• Simulating observations from a forthcoming eight-station EHT array.

Main Results:

• Updated constraints on the quadrupolar deviation of Sagittarius A*.
• Simulated high-precision measurements of spin magnitude (0.005), inclination (0.09°), position angle (0.04°), and quadrupolar deviation (0.005) at 3σ confidence with a one-day observation.
• Demonstrated the capability for precise strong gravity measurements.

Conclusions:

• The EHT is entering an era of high-precision strong gravity measurements.
• Future EHT observations will significantly enhance our understanding of black hole physics.
• The study validates the EHT's role in testing fundamental physics in extreme environments.