The newly-discovered galaxy, SPT0418-SE, and its much larger companion, SPT0418-47, reside in a massive dark-matter halo with yet-to-be-discovered neighbors, according to a new study.
Scanning the first images of SPT0418-47, a well-known strongly-lensed galaxy taken by the NASA/ESA/CSA James Webb Space Telescope, Cornell University astronomer Bo Peng and colleagues were intrigued to see a blob of light near its outer edge.
SPT0418-47’s light was bent and magnified by a foreground galaxy’s gravity into a circle, called an Einstein ring.
A deeper dive into the early Webb data released last fall produced a serendipitous discovery: a companion galaxy previously hidden behind the light of the foreground galaxy, one that surprisingly seems to have already hosted multiple generations of stars despite its young age, estimated at 1.4 billion years old.
“We found this galaxy to be super-chemically abundant, something none of us expected,” Peng said.
“Webb changes the way we view this system and opens up new venues to study how stars and galaxies formed in the early Universe.”
“Earlier images of the same Einstein ring captured by the Atacama Large Millimeter/submillimeter Array (ALMA) contained hints of the companion resolved clearly by JSWT, but they couldn’t be interpreted as anything more than random noise,” said Dr. Amit Vishwas, an astronomer at Cornell University.
Investigating spectral data embedded in each pixel of images from Webb’s NIRSpec instrument, the astronomers identified a second new light source inside the ring.
They determined that the two new sources were the images of a new galaxy being gravitationally lensed by the same foreground galaxy responsible for creating the ring, although they were eight to 16 times fainter.
Further analysis of the light’s chemical composition confirmed that strong emission lines from hydrogen, nitrogen and sulfur atoms displayed similar redshifts — a measure of how much light from a galaxy…
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