Astronomers from the University of Chicago have obtained a unique close-up view of the brightest gravitationally magnified galaxy cluster RCS2 032727-132623 yet discovered.
The images taken by researchers who used NASA's Hubble Space Telescope, offers a visually striking example of gravitational lensing, in which one massive object's gravitational field can magnify and distort the light coming from another object behind.
Such optical tricks stem from Einstein's theory of general relativity, which describes how gravity can warp space and time, including bending the path that light travels.
In this case, gravity from the galaxy cluster RCS2 032727-132623 bent and amplified the light coming from a much more distant galaxy, located 10 billion light-years from Earth.
This "gravitational telescope" creates a vast arc of light, as if the distant galaxy had been reflected in a funhouse mirror.
The UChicago team reconstructed what the distant galaxy really looks like, using computational tools that reversed the effect of gravitational lensing.
"What's happening here is a manifestation of general relativity," Michael Gladders, assistant professor in astronomy and astrophysics at Uchicago, said.
"Instead of seeing the normal, faint image of that distant source, you see highly distorted, highly magnified, and in this case, multiple images of the source caused by the intervening gravitational mass," he said.
The reconstructed image of the galaxy revealed regions of star formation glowing like bright points of light. These are much brighter than any star-formation region in Earth's home galaxy, the Milky Way.
In 2006 the Chicago astronomers used the Very Large Telescope in Chile to measure the arc's distance and calculated that the galaxy appears more than three
times brighter than previously discovered lensed galaxies.
Compass and Scale Image of Galaxy Cluster RCS2 032727-132623. Image Credit: NASA, ESA, J. Rigby (NASA Goddard Space Flight Center), and
K. Sharon (Kavli Institute for Cosmological Physics, University of Chicago), and M. Gladders and E. Wuyts (University of Chicago)
Last year, Jane Rigby of NASA's Goddard Space Flight Center in Greenbelt, Md., and the Chicago team imaged the arc with the Hubble Space Telescope's Wide Field Camera 3.
According to Gladders, using this gravitational lens as a telescope offers two major scientific opportunities. First, "It gives us a look at that very distant source with a precision and fidelity that we couldn't otherwise achieve."
Secondly, it provides an opportunity to learn something about the lens-forming mass, which is dominated by dark matter.
"It's really a way of looking at the nature of dark matter," Gladders said.
This graphic shows a reconstruction (at lower left) of the brightest galaxy whose image has been distorted by the gravity
of a distant galaxy cluster. The small rectangle in the center shows the location of the background galaxy on the sky if the
intervening galaxy cluster were not there. The rounded outlines show distinct, distorted images of the background galaxy
resulting from lensing by the mass in the cluster. The image at lower left is a reconstruction of what the lensed galaxy
would look like in the absence of the cluster, based on a model of the cluster's mass distribution derived from studying
the distorted galaxy images.Credit: NASA, ESA, J. Rigby (NASA Goddard Space Flight Center), K. Sharon (Kavli Institute
for Cosmological Physics, University of Chicago), and M. Gladders and E. Wuyts (University of Chicago)
Dark matter accounts for nearly 90 percent of all matter in the universe, yet its identity remains one of the biggest mysteries of modern science.
Keren Sharon, a postdoctoral scholar at Uchicago's Kavli Institute for Cosmological Physics, led the effort to perform a detailed reconstruction of the lensed galaxy.
Sharon painstakingly created a computer reconstruction of the gravitational lens, then reverse-engineered the distorted image to determine the distant galaxy's actual appearance.
"It was a fun puzzle to solve, especially when we had such great data," Keren Sharon said.
Through spectroscopy, the spreading out of light into its constituent colours, the team plans to analyse the distant galaxy's star-forming regions from the inside out to better understand why they are forming so many stars.
The team also has obtained data from one of the twin Magellan Telescopes to help them determine why the galaxy, which is 10 billion light years away, looks so irregular.
"It's not like we have something to compare it to.
"We don't know what other galaxies at the same distance look like at this level of detail," she added.
The study has been published in Astrophysical Journal. (ANI)
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