A collision 7 billion years ago and a surge of magnification. Look at that in infrared, and somehow you end up with a question mark. It was a combination of a galaxy merger being located near the line of sight of a massive galaxy cluster that is distorting its light, creating something that has been seen maybe only three or four times before.
The system in question is galaxy cluster MACS-J0417.5-1154. Its massive central galaxy is warping space-time around it, creating an effect called gravitational lensing. The warp is magnifying the light of a galaxy interaction: a red galaxy and a bluish galaxy are becoming intimately acquainted. And due to the gravitational lens, you can see their image five times.
Two images make the curve top of the question mark. Two more images are extremely distorted around the massive bright galaxy that caused the lens in the middle. It would be poetic if the fifth image was the dot on the question mark, but that is an unrelated galaxy. The actual image is to the right next to a thin blue galaxy.
Hubble (top) versus JWST (bottom) images of the same galaxies. The galaxy merger becomes immediately obvious in the more recent image.
Image Credit: NASA, ESA, CSA, STScI, Vicente Estrada-Carpenter (Saint Mary’s University)
“This is just cool looking. Amazing images like this are why I got into astronomy when I was young,” astronomer Marcin Sawicki of Saint Mary’s University, one of the lead researchers on the team, said in a statement.
The system has already been observed in ultraviolet light using Hubble, but the infrared observations with JWST add a lot more information about these distant objects. Both infrared and ultraviolet are crucial to studying star formation over the ages of the universe.
In turn, “knowing when, where, and how star formation occurs within galaxies is crucial to understanding how galaxies have evolved over the history of the universe,” added astronomer Vicente Estrada-Carpenter of Saint Mary’s University.
Star formation is widespread in both merging galaxies but their shape is not massively distorted, when you correct the distortion from the gravitational lens. They might shape a question mark at first glance, but the team knows what’s going on with them.
“Both galaxies in the Question Mark Pair show active star formation in several compact regions, likely a result of gas from the two galaxies colliding,” said Estrada-Carpenter. “However, neither galaxy’s shape appears too disrupted, so we are probably seeing the beginning of their interaction with each other.”
A paper detailing star formation in these galaxies is published in the Monthly Notices of the Royal Astronomical Society.
