James Webb Space Telescope finds ‘engine’ powering the merger of galaxies

The engine is responsible for up to 70 per cent of the total infrared emission of the system.

Astronomers used the JWST to reveal the location of the source powering colliding galaxies. It lies outside the galaxies’ main parts and is not visible using UV light. | Photo Credit: Hanae Inami, Hiroshima University

Twelve years ago, astronomers identified the source of a very bright phenomenon near the constellation Delphinus where two galaxies are colliding. But cosmic dust obscured the details. Now, with the James Webb Space Telescope (JWST), researchers have pinpointed the precise location of what they have dubbed the “engine” of the merging galaxy. The finding was reported in The Astrophysical Journal Letters.

“JWST has brought us completely new views of the universe thanks to it having the highest ever spatial resolution and sensitivity in the infrared [emphasis added],” the main author Hanae Inami of Hiroshima University’s (HU) Hiroshima Astrophysical Science Center was quoted as saying by the centre’s press release on February 6. “We wanted to find the ‘engine’ that powers this merging galaxy system. We knew that this source was deeply hidden by cosmic dust, so we could not use visible or ultraviolet light to find it. Only in the mid-infrared [IR], observed with JWST, do we now see that this source outshines everything else in these merging galaxies.” Most galactic collisions only emit IR light, which has longer wavelengths than visible light.

The engine was found to be responsible for up to 70 per cent of the total IR emission of the system.

The researchers also found that the source had a radius no larger than 570 light years. “It is intriguing that this compact source, far from the galactic centres, dominates the IR luminosity of the system,” said Thomas Bohn, of HU and co-author of the paper. “We want to know what powers this source: is it a starburst or a massive black hole?” Inami asked. “We will use infrared spectra taken with JWST to investigate this... we will explore how this powerful source ended up there.”

Co-author Jason Surace of the California Institute of Technology said: “The last few decades, driven by new, mostly space-based observations in the infrared, have shown that the universe is a surprisingly dynamic and violently changing place.”