Astronomers have recently discovered two galaxies in the early universe in the process of merging, which will eventually form a single bright and massive galaxy, resembling a “cosmic giant”.
According to a press release from the National Astronomical Observatory of Japan on August 30, scientists have identified two galaxies merging from 12.8 billion years ago. The characteristics of these two galaxies indicate that they will form a giant galaxy, one of the brightest types of celestial bodies in the universe.
Scientists believe that the universe was born after the Big Bang 13.8 billion years ago, with a history spanning 13.8 billion years. The merging of these two galaxies holds significant importance for understanding the early evolution of galaxies and the supermassive black holes in the early universe.
In this study, Associate Professor Yoshiki Matsuoka from Ehime University in Japan first discovered two early universe quasars using the Subaru Telescope. These quasars are located in the direction of Virgo, approximately 12.8 billion light-years away from Earth.
Quasars are extremely bright cores in distant galaxies, powered by supermassive black holes. These black holes absorb material from their surroundings and emit a large amount of light, making quasars one of the brightest celestial objects in the sky.
However, the two quasars observed by Matsuoka were dim, indicating that they are still in the early stages of evolution.
The most widely accepted theory suggests that when two gas-rich galaxies merge into a larger single galaxy, the gravitational interaction between the two galaxies can cause gas to fall into one or both supermassive black holes, triggering quasar activity.
To confirm this theory, Associate Professor Takuma Izumi’s research team at the National Astronomical Observatory of Japan used the Atacama Large Millimeter/submillimeter Array (ALMA) radio telescope in Argentina to study the two earliest known quasars and their host galaxies.
They found that the distribution of interstellar material (the bridge-like structure composed of gas and dust connecting these two galaxies) and its motion clearly indicate that these galaxies are interacting and will merge into a single galaxy.
Moreover, calculations based on observational data showed that the total gas mass of these galaxies (approximately 100 billion times the mass of the Sun) is comparable to or even greater than that of the host galaxies of the brightest quasars.
With such large amounts of material, the explosive formation of stars and the energy provided by supermassive black holes should occur and be sustained easily before the merger of these two galaxies. The combination of starburst activity and active quasar activity is expected to create a bright and massive galaxy in the early universe.
Expressing his excitement over these research findings, lead researcher Takuma Izumi stated, “When we first observed the interaction between these two galaxies, it was like watching a dance, with their central black holes beginning to grow.”
He looks forward to further research in the future, mentioning that through the Subaru Telescope and ALMA, they have started to understand the properties of the gas surrounding these supermassive black holes and their host galaxies. However, the properties of stars within the host galaxies remain unknown.
He noted that future insights into the stellar properties of these objects can be obtained through the James Webb Space Telescope.
He added, “As ancestors of the high-luminosity quasars that researchers have long sought, they should serve as valuable cosmic laboratories. I hope that through various observations, we can deepen our understanding of their nature and evolution in the future.”