While studying young galaxies at a distance of 11.6 billion light-years from Earth, a team of astronomers has noticed a strangely shaped galaxy that looks like a magatama, an ancient, comma-shaped Japanese amulet made of stone.
Subsequent research revealed that the magatama galaxy was actually an overlapping system of two young galaxies lying in an extremely close line of sight -- an exceedingly rare occurrence among celestial objects.
The small angular separation between the foreground and background galaxies gave the current team an opportunity to investigate the effect of gravitational lensing on the properties of the background galaxy.
A member of the team, university student Yuya Nakahiro (Ehime University), calculated that the effect of gravitational amplification would be 20 percent at most.
The foreground young galaxy is still forming, and the team led by Professor Yoshiaki Taniguchi (Ehime University) concluded that the gravitational lensing effect from such a young galaxy does not affect the luminosity of its background galaxy.
The focus of the team’s research was the young galaxy LAE 221724+001716, which lies about 11.6 billion light-years distant from the Earth.
Team member Dr. Akio Inoue (Osaka Sangyo University) had made observations with the Subaru Telescope’s prime focus camera (Suprime-Cam) and identified this galaxy as one of those emitting strong ultraviolet radiation that ionizes hydrogen atoms (Note); it is a Lyman-alpha emitter (LAE) and can provide important clues about the progenitors of Milky-Way type galaxies.
Although he noticed that there was a separation between the galaxy itself and the emission point of ionizing radiation, he concluded that this galaxy did not include the effect of any foreground galaxies, given the negligible probability of an overlapping foreground galaxy with such a small separation from its background galaxy.
However, another research team using Keck’s Low Resolution Imaging Spectrometer (LRIS) found that the radiation, originally interpreted as ionizing radiation from LAE 221724+001716, came from a foreground galaxy located about 9.9 billion light-years from Earth.
Dr. Inoue expressed his surprise at the finding: “This result was very amazing to me, since this is the discovery of an extremely rare system.”