A young galaxy has been discovered.
The new results, obtained by combining big data from the Subaru telescope and machine learning capabilities, revealed a galaxy with an extremely low oxygen content of 1.6%, breaking the previous record. The measured amount of oxygen suggests that most of the stars in this galaxy formed very recently.
To understand the evolution of a galaxy, astronomers need to study galaxies at various stages of formation and evolution. Most of the galaxies in the modern universe are mature galaxies, but standard cosmology predicts that there may still be a few galaxies in the early stage of formation in the modern universe.
Since these early galaxies are quite rare, the international research team looked for them in the data obtained with the Subaru telescope. ” To find very rare galaxies, we needed data that could only be obtained with the Subaru telescope, ” says Dr. Takashi Kojima, the team leader.
However, it is difficult to find galaxies at an early stage of formation, because the data obtained from the Subaru telescope can include up to 40 million objects. So the research team developed a new machine learning method to find such galaxies from a huge amount of data, sifting out other galaxies. They had a computer that tracked the desired galaxy colors expected from theoretical models, and then allowed the computer to select only galaxies at an early stage of galaxy formation.
The research team then used a computer to discover that one galaxy (HSC J1631+4426), located 430 million light-years away in the constellation Hercules, has an oxygen content of just 1.6 percent of the solar system’s oxygen content. This is the lowest value ever measured for a galaxy. The amount of oxygen suggests that most of the stars in this galaxy formed very recently. In other words, this galaxy is at an early stage of evolution.
“What is surprising is that the stellar mass of the galaxy HSC J1631+4426 is very small, 0.8 million solar masses. This stellar mass is only about 1/100, 000 of our Milky Way galaxy, ” says Professor Ouchi of the National Astronomical Observatory of Japan and the University of Tokyo. This small mass also supports the primordial nature of the galaxy HSC J1631+4426.
The research team believes that there are two interesting parameters. First, it is the most significant evidence of the existence of a galaxy at such an early stage of evolution. Within the framework of standard cosmology, it is believed that new galaxies are still being born in the current universe. The discovery of the galaxy HSC J1631+4426 confirms the picture of standard cosmology. Secondly, we can observe a newborn galaxy in the last epoch of cosmic history. Standard cosmology assumes that the density of matter in the universe falls rapidly as the expansion of the universe accelerates. In a future universe, with rapid expansion, matter will not gather through gravity and new galaxies will not evolve. Galaxy HSC J1631+4426 may represent the latest generation of galaxies to evolve in cosmic history.