Webb images trace gas stream feeding a supermassive black hole
Astronomers say JWST observations of NGC 4696 show cool gas flowing into a disk around its central black hole.
By Priya Raghavan · Science Reporter
3 min read
The James Webb Space Telescope has captured unusually detailed evidence of gas moving toward a supermassive black hole in NGC 4696, according to Michigan State University. The observations matter because they support a leading explanation for how active black holes keep finding fuel even as their jets heat the gas around them.
An international team led by the Université de Montréal, with Michigan State University researchers contributing, reported the findings in the July 14 issue of The Astrophysical Journal Letters. The group studied NGC 4696, the largest central galaxy in the Centaurus Cluster, which Michigan State said is about 145 million light-years from Earth.
Michigan State said JWST images show extended gas structures connecting the galaxy’s hot outer atmosphere with a fast-spinning disk near the black hole. That disk is the last major holding area for material before it moves inward and helps power the black hole’s activity.
A close look at a galactic center
The researchers used JWST’s NIRSpec instrument to observe NGC 4696 for nearly eight hours, according to Michigan State. NIRSpec breaks infrared light into wavelengths that allow astronomers to measure gas motion, composition and physical conditions across a target.
The resulting maps reached into the region where the black hole’s gravity controls nearby material, Michigan State said. JWST resolved features about 30 light-years across, a fine scale for work inside a galaxy that extends across far larger distances.
The team found that an S-shaped feature near the galaxy’s core is a rotating gas disk around the supermassive black hole, according to the university. The disk is nearly 800 light-years wide, and some gas in it moves at up to 600 kilometers per second.
The key observation, Michigan State said, is that the disk appears connected to a larger filament carrying gas inward. The data show material moving along the filament and entering the disk that supplies the black hole.
A possible fuel cycle
Most large galaxies contain supermassive black holes at their centers, according to Michigan State. When gas and dust fall toward one of these objects, the material can heat up and create an active galactic nucleus, which can drive jets that send energy into the surrounding galaxy.
Those jets can heat nearby gas and affect star formation, Michigan State said. That has left astronomers with a problem: if the black hole’s activity warms its surroundings, the supply of cool gas should become harder to maintain.
The new study supports a self-regulating cycle, according to the researchers. Gas heated by black hole activity may later cool, condense into narrow filaments and fall back toward the center, where it can feed the black hole again.
Megan Donahue, a University Distinguished Professor of physics and astronomy at Michigan State, said JWST is providing many new measurements as researchers study how black holes get fuel and interact with their host galaxies. Mark Voit, a Michigan State physics and astronomy professor, said calculations by the university’s group predicted that magnetic fields could help guide cool gas toward the largest black holes.
The team also used computer simulations to compare with the JWST data, according to Michigan State. The simulations produced gas behavior similar to what Webb observed, supporting the idea that cooling gas, magnetic fields and black hole jets can work together in a repeating feedback cycle.
This story draws on original reporting from ScienceDaily.