X-ray and Radio Study Links Hot Plasma to Relativistic Jet Launch

X-ray and radio observations of the active galaxy 3C 120 show that a rapidly accreting supermassive black hole is surrounded by the conditions associated with launching a relativistic jet: a cold, flat accretion disk that gives way to hot plasma close to the black hole. A research team led by Associate Professor Hirofumi Noda of Tohoku University and Associate Professor Kazuhiro Hada of Nagoya City University combined measurements from the X-Ray Imaging and Spectroscopy Mission, or XRISM, with observations from three radio interferometry networks. The study connects the black hole’s immediate environment with the narrowing stream of plasma expelled at nearly the speed of light, although it is based on one active galaxy rather than a broad sample of black holes.

The team examined 3C 120, an active galaxy in the constellation Taurus whose central supermassive black hole rapidly consumes surrounding matter while producing a powerful jet. This creates a physical puzzle because rapid feeding is expected to form a cold, relatively flat accretion disk, which can prevent powerful jets from forming. XRISM detected an iron emission line from the disk surrounding the black hole. The shape of the line was distorted by the effects of Einstein’s general relativity, allowing the researchers to determine how far inward the disk extends toward the black hole.

The iron-line profile indicated that the cold disk ends at approximately 20 times the black hole’s radius. Beyond that point, it transitions into a hot flow of plasma reaching temperatures of hundreds of millions of degrees. At the same time, radio and millimeter observations from the Global Millimeter VLBI Array, the Very Long Baseline Array and the East Asian VLBI Network traced the narrowing jet back to its origin within this hot flow, close to the black hole. By examining the same system with X-ray and radio instruments, the researchers linked two measured properties: the position where the accretion disk is truncated and the position from which the jet emerges.

The findings support a magnetic explanation for jet launching. The hot environment near 3C 120’s black hole can allow magnetic fields to accumulate around the black hole, where they may extract some of its rotational energy and channel it into the powerful outflow. The observations do not directly measure the full sequence of this process or every component of the proposed mechanism, but they demonstrate that 3C 120 has the hot flow, close-in jet base and disk structure required for it to operate. The result therefore identifies physical conditions compatible with relativistic jet launching in this highly accreting system; it does not establish that all rapidly feeding supermassive black holes launch jets in the same way.

Published in Astrophysical Journal Letters on October 19, 2026, the study also offers an approach for examining the immediate surroundings of supermassive black holes through coordinated X-ray and radio observations. The team is conducting further observations of a more massive black hole with XRISM and global radio observatories, with the aim of comparing the results with theoretical models and computer simulations. A fuller understanding of how matter, magnetic fields and black-hole rotation interact in these extreme environments may also improve explanations of how supermassive black holes influence the evolution of galaxies and larger structures in the universe.

Subject of Research: Multiwavelength observations of disk truncation and relativistic jet launching around the supermassive black hole in 3C 120.

Article Title: What drives the jets fired from hungry supermassive black holes?

Article References: What drives the jets fired from hungry supermassive black holes?. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: supermassive black holes, relativistic jets, accretion disks, 3C 120, XRISM, radio interferometry, general relativity, magnetic fields, active galaxies, hot accretion flows, drives, jets