Webb Looked Through the Dust at the Squid Galaxy's Black Hole and Found an Outflow Up to 100 Times More Powerful Than Anyone Had Measured. Most of the Gas Was Invisible to Optical Telescopes.

One of the most-observed galaxies in the sky has been hiding most of what its central black hole is doing. Astronomers using the James Webb Space Telescope have found that NGC 1068, a barred spiral 45 million light-years away also known as Messier 77 or the Squid Galaxy, is driving a wind of ionized gas from its core that carries up to 100 times more mass, energy and momentum than standard methods had estimated. The bulk of it was simply invisible at optical wavelengths.

The work, led by Cosimo Marconcini of the University of Florence and published Aug. 6 in Astronomy & Astrophysics, is the third paper in a program called MIRACLE that uses Webb's Mid-Infrared Instrument to look at active galaxies. NGC 1068 hosts a supermassive black hole of between 8 million and 17 million solar masses that is actively feeding, and as matter spirals in it releases enough energy to blow gas outward. Those outflows heat and expel the raw material for new stars and can starve the black hole itself, which is why astronomers treat them as a central regulator of how galaxies grow.

The trouble is measuring them. Much of the gas near an active nucleus sits behind thick dust, which blocks visible light. Mid-infrared light passes through dust far more easily, so the team combined new MIRI integral-field spectroscopy with archival optical data from the VLT's MUSE instrument and millimeter-wave data from ALMA. The infrared spectra revealed more than 20 ionized-gas emission lines and seven transitions of warm molecular hydrogen.

Using ratios of optical and infrared lines, the researchers first confirmed that the wind is powered by the black hole and not by star formation. Then they found it has two parts. One is the component optical telescopes have seen for decades. The other is shrouded in dust, shows up only in the infrared, moves roughly 300 kilometers per second faster and carries most of the outflow's total mass. The fastest gas reaches about 2,000 kilometers per second, or roughly 4.5 million miles per hour.

With two specialized modeling tools, the team recalculated the outflow's energetics and found them up to 100 times larger than conventional estimates. Several million solar masses of ionized gas are being pushed out of the galaxy's center. Comparing the gas speed to NGC 1068's escape velocity, they found the wind is moving several times faster than needed to leave, so some of that material will never fall back.

The momentum turned out to be more than the black hole's radiation alone should produce. NGC 1068 also has a radio jet aligned with the outflow, and the authors suggest it is doing mechanical work on the gas. "The large outflow energetics also suggests a possible contribution from the co-spatial radio jet in driving the outflowing gas and injecting large mechanical work," they write.

The broader implication is uncomfortable for a field that has built much of its picture of black hole feedback on optical measurements. "Our findings illustrate the drastic change of scenario that can emerge when properly evaluating the true outflow energetics," the researchers write. If a galaxy as well studied as NGC 1068 was hiding most of its wind, the standard census of how much gas black holes throw out of their hosts may be badly incomplete, and mid-infrared observations paired with careful modeling may be the only way to fix it.