Supermassive Black Hole Jet Formation Linked to Inner Disk Transition

• Researchers have discovered that supermassive black holes (SMBHs) launch relativistic jets by transitioning from a cold, thin outer accretion disk to a hot, thick inner disk.
• This "truncated" disk structure resolves a long-standing paradox regarding how rapidly accreting black holes generate the magnetic fields required for jet launching.

Research Findings

• A study of the active galaxy 3C 120, located 420 million light-years away, revealed that its accretion disk is truncated at approximately 20 gravitational radii (Rg).
• The inner region consists of a hot, geometrically thick flow capable of sustaining the large-scale magnetic fields required by the Blandford–Znajek (BZ) mechanism to extract rotational energy from the black hole.
• Observations utilized advanced instruments including the X-ray Imaging and Spectroscopy Mission (XRISM) and multiple Very Long Baseline Interferometry (VLBI) arrays to map both the hot plasma and the emerging jet.

Implications

• The study confirms the universal nature of the disk-jet connection through geometric structural transitions.
• By verifying how magnetic fields are sustained even at high accretion rates, scientists gain insight into how SMBHs influence galaxy evolution and large-scale cosmic structures.
• Future research will apply this multi-observatory methodology to a broader sample of black holes to further refine the model of black hole magnetohydrodynamics.