“This particular discovery is important because we have all these all models on how (galaxies) should form, but because we have this discrepancy between what we observe and what the models say, we don’t know if the models are right,”
BY CHELSEA JENSEN
WEST HAWAII TODAY
cjensen@westhawaiitoday.com
Astronomers using the Keck II telescope atop Mauna Kea have discovered what they say is the most distant dwarf galaxy.
The dwarf galaxy is an interesting find as larger galaxies — including the Milky Way Galaxy — are believed to have formed over billions of years through the merging of many smaller, dwarf galaxies, said Chris Fassnacht, an astronomer with the University of California at Davis’ physics department, who took part in the recent discovery. Though it’s believed the Milky Way Galaxy contains about 10,000 dwarf galaxies, only 30 have been observed thus far.
“It’s a step in learning how our own galaxy formed,” Fassnacht said Wednesday. “The idea of all these thousands of things merging together is well established from the computer simulations that people have done, but the problem has been that we haven’t seen these thousands of satellite (dwarf) galaxies when we look out around us.
“If (we can study these galaxies) and get a picture that is also consistent with the computer models, then we will understand how galaxies form.”
A team of astronomers using Keck II telescope’s adaptive optics announced Wednesday the discovery of the dwarf galaxy halfway across the universe. The new dwarf galaxy found by Massachusetts Institute of Technology Theoretical Astrophysicist Simona Vegetti and colleagues is a satellite of an elliptical galaxy almost 10 billion light-years from Earth, according to the W. M. Keck Observatory.
The team detected the dwarf galaxy by studying how a massive elliptical galaxy, called JVAS B1938 + 666, serves as a gravitational lens for light from an even more distant galaxy directly behind it. The discovery was published in the Wednesday online edition of the journal Nature.
By using the 10-meter Keck II’s adaptive optics, which cancels out much of the interference caused by Earth’s atmosphere, Fassnacht said astronomers were able to view the massive galaxy, which deflects light passing by it creating a ring referred to as the “Einstein Ring.”
The researchers then used distortions within that ring to find evidence of the low-mass dark galaxy, or dwarf galaxy, he said. Using a mapping model, astronomers could attribute the mass seen in the ring only to the presence of a dwarf galaxy.
“Using gravitational lensing we can study the effect of light from a more distant object as it passes by a galaxy allowing us to see any dwarf galaxies around,” Fassnacht said. “Even if there were zero stars in (the dwarf galaxy) we would know that it is there.”
And, knowing that the dwarf galaxy is there is the most important aspect uncovered by the team as it opens the doors to further study into galaxies and how the Milky Way Galaxy was formed, Fassnacht said. However, the find wouldn’t have come had it not been for the Keck II’s telescope’s adaptive optics, he added.
“This particular discovery is important because we have all these all models on how (galaxies) should form, but because we have this discrepancy between what we observe and what the models say, we don’t know if the models are right,” he said. “The next step is to go out and use these adaptive optics systems to get more statistics so we then can test theories.”
