2021-10-09

“Double” galaxies puzzled astronomers: “we’re really baffled.”

By yqqlm yqqlm

“Double” galaxies puzzled astronomers: “we’re really baffled.”

these features puzzled astronomers so much that it took them years to solve the mystery. With the help of two gravitational lensing experts, the researchers determined that the three celestial bodies were distorted images of a distant, undiscovered galaxy. But the biggest surprise is that these linear objects are accurate “copies” of each other, which is a rare case caused by the precise arrangement of background galaxies and foreground lens clusters

astronomers have seen some rather strange things scattered in our vast universe, from exploding stars to colliding galaxies. Therefore, people may think that when they see a strange celestial body, they will be able to recognize it. But NASA’s Hubble Space Telescope found what appeared to be two identical objects. They looked so strange that it took astronomers years to determine what they were

astronomer Timothy Hamilton of Shawnee State University (Portsmouth) said, “we’re really stumped.”. These strange objects consist of a pair of galactic bulges (the central hub of a galaxy full of stars) and at least three almost parallel splitting stripes. Hamilton accidentally found them when he used Hubble to measure the collection of quasars, the hot core of active galaxies

after Hamilton asked his colleagues for help and did a lot of work, Hamilton and the team led by Richard Griffith of the University of Hawaii at Shiloh finally put all the clues together and solved the mystery. These linear objects are stretched images of a gravitationally condensed distant galaxy located more than 11 billion light-years away. Moreover, they seem to mirror each other

the research team found that the huge gravity of an involved, non catalogued foreground galaxy cluster is distorting space, magnifying, brightening and stretching the image of a distant galaxy behind it. This phenomenon is called gravitational lens. Although Hubble observations reveal many of these interesting mirror distortions caused by gravitational lenses, the object is confusing

in this case, the precise arrangement between a background galaxy and a foreground galaxy cluster produces a double enlarged copy of the same image of the distant galaxy. This rare phenomenon occurs because the background Galaxy crosses a ripple in the spatial structure. This “ripple” is the largest amplification area, caused by the gravity of dense dark matter, which is the invisible glue that makes up most of the mass of the universe. When light from distant galaxies passes through the cluster along this ripple, two mirrors are produced, and a third image biased to one side can be seen

Griffith compares this effect to the bright wavy pattern seen at the bottom of the swimming pool. “Think about the ripples on the surface of the swimming pool on a sunny day, showing a bright pattern at the bottom of the pool,” he explained. “These bright patterns at the bottom are caused by an effect similar to gravitational lens. Ripples on the surface act as a partial lens to focus sunlight on the bright grid pattern at the bottom.”

in distant galaxies of gravitational lens, “ripple” greatly amplifies and distorts the light passing through the background galaxies of the galaxy cluster. The “ripple” acts like an imperfect curved mirror, producing a double copy

but when Hamilton discovered these strange linear features in 2013, this rare phenomenon was not known. When he flipped through quasar images, mirror images and snapshots of parallel stripes stood out. Hamilton has never seen anything like this before, nor have other team members

Hamilton said: “my first thought is that maybe they are interacting galaxies with tidal stretching arms. This is not suitable, but I don’t know what else to think.”

so Hamilton and his team began their exploration to solve these attractive straight-line mysteries, which were later called “Hamilton objects” because of their discoverers. They showed their colleagues this strange image at the astronomical conference, which caused a variety of reactions, from cosmic strings to planetary nebulae

“Double” galaxies puzzled astronomers: “we’re really baffled.”(1)

however, when Hamilton presented the image at a NASA meeting in 2015, Griffith, who was not the original team member, put forward the most reasonable explanation. This is an enlarged and distorted image caused by lens phenomena similar to other massive galaxy clusters seen in the Hubble image. These galaxy clusters are magnifying the image of very distant galaxies. Griffith confirmed this idea when he learned about a similar linear object in a Hubble survey of deep galaxy clusters

however, researchers still have a problem. They can’t identify lens clusters. Usually, astronomers studying galaxy clusters first see the foreground galaxy cluster that causes the lens, and then find an enlarged image of distant galaxies in the galaxy cluster. A search of the Sloan Digital Sky Survey image showed that a galaxy cluster was located in the same area as the enlarged image, but it did not appear in any catalog survey. Nevertheless, the fact that these strange images are located at the center of a galaxy cluster makes Griffith clearly realize that the galaxy cluster is producing condensed images

the researchers’ next step is to determine whether the three condensed images are at the same distance, so whether they are distorted portraits of the same distant galaxy. Spectral measurements from the Gemini telescope in Hawaii and the W.M. Keck Observatory helped researchers make this confirmation, showing that the condensed image came from a galaxy more than 11 billion light-years away

according to the reconstruction of the third condensed image, the distant galaxy seems to be a strip spiral on the edge, with continuous and caked star formation

while Griffith and undergraduates at the University of Hawaii Hilo made spectral observations, another group of researchers in Chicago used Sloan data to determine the star cluster and measure its distance. The cluster lies more than 7 billion light-years away

however, because there is very little information about the cluster, Griffith’s team is still trying to explain these unusual lens shapes. “This gravitational lens is very different from most of the lenses previously studied by Hubble, especially in the star clusters investigated in Hubble’s frontier field,” Griffith explained. “You don’t have to stare at those star clusters for a long time to find many lenses. In this celestial body, this is our only lens. At first, we didn’t even know this star cluster.”

then Griffith contacted Jenny Wagner of Heidelberg University, an expert in gravitational lens theory. Wagner has studied similar objects and developed computer software to explain unique lenses like this, along with researcher Nicholas tesoray of the University of Manchester, now in the UK. Their software helped the team figure out how all three lens images were formed. They concluded that the dark matter around the stretched image must be “smoothly” distributed in space on a small scale

“well, we only need two mirrors to get the scale of dark matter caking or non caking at these locations,” Wagner said. “Here, we don’t use any lens model. We just take the observation data of multiple images and the fact that they can be converted to each other. They can be folded into one by our method. This has given us an idea of how smooth dark matter needs to be in these two positions.”

Griffith said that this result is very important, Because astronomers still don’t know what dark matter is nearly a century after they discovered it. “We know that it is some form of matter, but we don’t know what its constituent particles are. So we don’t know how it behaves at all. We only know that it has mass and is affected by gravity. The significance of the size limit on agglomeration or smoothness is that it provides us with some clues about what particles may be. The smaller the dark matter mass, the more the mass of particles The bigger it must be

the team’s paper was published in the monthly journal of the Royal Astronomical Society in September