Today's heaviest galaxies are elliptical, but many are said to have once rotated in a disk shape like the Milky Way galaxy.How did the ancient galaxy change its shape?An international team led by Kenichi Tadaki, a research fellow at the National Astronomical Observatory of Japan, Maxplank Institute of Extraterrestrial Physics, and Professor Tadayasu Kodama of Tohoku University, has a new star in the center of the galaxy 110 billion light-years away. I found out that it was born explosively.This intense star-forming activity was responsible for the galaxy's transformation from a disk to an ellipse.
Many of the stars in the galaxy were born 100 to 110 billion years ago.Galactic surveys during this period observe galaxies 110 billion light-years away, but distant galaxies are very small and the light is weak, so observation is difficult.Even with the observation of the Subaru Telescope with a diameter of 8.2 m, the galaxy can only be seen as a point.
So the research team first used the Subaru Telescope to search for galaxies 110 billion light-years away.The 25 galaxies discovered were observed with the Hubble Space Telescope of NASA, which has three times the resolution of the Subaru telescope, and the ALMA telescope jointly operated by Japan, the United States, and Europe, and the internal structure was drawn. ..
The galaxy 110 billion light-years away from the Hubble Space Telescope was a large disk, not yet an ellipse.However, analysis of high-resolution data by ALMA reveals that new stars are exploding in the center of these galaxies.It could be interpreted that this caused a change from a disk shape to an elliptical shape.
Currently, the theory of collision coalescence that "disk-shaped galaxies collide and coalesce and evolve into an elliptical galaxy" is the established theory, but there are no signs of large-scale coalescence in the galaxies observed this time.The significance of this research result is that we have found definitive evidence that the galaxy had another evolutionary pathway (star formation activity) that does not collide and coalesce.
Paper information:
[The Astrophysical Journal] BULGE-FORMING GALAXIES WITH AN EXTENDED ROTATING DISK AT z ~ 2
[The Astrophysical Journal Letters] Rotating Starburst Cores in Massive Galaxies at z = 2.5 (PDF)
