Galaxies caught in the act of merging their blackholes

by | June 2, 2024, 9:00 AM | Galaxies & Cosmology

As we head toward summer, JWST is getting ready to start its second year of science operations. During its brief period of operations, this $8.8 billion spacecraft has been working hard to prove it can do science worthy of its price tag.

Adding to it’s list of accomplishments is ESA’s May 16 announcement that JWST had discovered a pair of merging galaxies with clear evidence of imminent black hole merger.

The system was found while analyzing data from the JWST PRIMER program, a large area survey designed for extragalactic research. 

The system is cataloged a ZS7 and its light is shining toward us from when the universe was just 740 million years old.

On its own, it doesn’t look like much- just another red smear of light shining at us from the early universe. Analysis of spectra – which spread the light out and allow us to study composition and motions in detail – allowed researchers to realize there is fast moving gas and a pair of active blackholes.

This work is published in the Monthly Notices of the Royal Astronomical Society with Hannah Ubler as first author. 

According to Ubler, “We found evidence for very dense gas with fast motions in the vicinity of the black hole, as well as hot and highly ionized gas illuminated by the energetic radiation typically produced by black holes in their accretion episodes. JWST also allowed our team to spatially separate the two black holes.

One black hole is measured to have a mass 50 million times the mass of the Sun. The other is estimated to be the same size but is harder to measure due to obscuring gas. 

Ubler explains “Our findings suggest that merging is an important route through which black holes can rapidly grow.” And with massive black holes come massive galaxies. With these images, we are watching the systems of today forming 13 billion years ago.

While this isn’t the first time imminent black hole mergers have been found through images, this technique certainly is less common than spotting in-action mergers through their gravitational waves. Stellar mass black holes and intermediate mass black holes in some situations can all be detected with the LIGO/Virgo and other gravitational wave detectors that are here on Earth. This particular merger, however, won’t be detectable with these systems – it will just rumble gravitationally at the wrong frequency. It may be detectable with systems like the planned LISA mission, to detect gravitational waves using spacecraft. I say systems like because this system won’t merge anytime in the next many generations of human lifetimes… but LISA will be able to detect systems like this and help us understand just how common these amazing mergers may be.