NASA astronomers used the Hubble telescope to discover the most distant known lensing galaxy.
Gravitational lensing occurs when a galaxy is so massive it bends and distorts light from the objects around it, acting as a sort of magnifying glass, NASA reported. The team found the galaxy in a small region of the sky; in most cases a large sky survey would need to be taken in order to make such a discovery. The discovery of distant lensing galaxies can help researchers gain insight into how galaxies form and dark matter. The findings will be published in the July 10 issue of The Astrophysical Journal Letters.
"When you look more than [nine] billion years ago in the early universe, you don't expect to find this type of galaxy lensing at all," said lead researcher Kim-Vy Tran of Texas A&M University in College Station. "It's very difficult to see an alignment between two galaxies in the early universe. Imagine holding a magnifying glass close to you and then moving it much farther away. When you look through a magnifying glass held at arm's length, the chances that you will see an enlarged object are high. But if you move the magnifying glass across the room, your chances of seeing the magnifying glass nearly perfectly aligned with another object beyond it diminishes."
The giant galaxy weighs 180 billion times more than our Sun, it is also one of the brightest in its cluster. Researchers believe the lensing galaxy grew over the past nine billion years, and acquired stars and dark matter by "cannibalizing" other galaxies. In the past researchers believed dark matter built up in galaxies equally over time, but these new findings suggest the ratio changes with time.
The galaxy was first discovered by when Tran and her team were studying star formation in distant galaxy clusters. They noticed hot hydrogen gas coming from a giant elliptical galaxy, which usually indicates a star birth. They then noticed distorted, magnified images behind that galaxy.
"There are hundreds of lens galaxies that we know about, but almost all of them are relatively nearby, in cosmic terms," said Wong, first author on the team's science paper. "To find a lens as far away as this one is a very special discovery because we can learn about the dark-matter content of galaxies in the distant past. By comparing our analysis of this lens galaxy to the more nearby lenses, we can start to understand how that dark-matter content has evolved over time."
