REBELS-25 existed as early as 700 million years after Big Bang, according to a paper published in the Monthly Notices of the Royal Astronomical Society.
This image shows the galaxy REBELS-25 as seen by ALMA, overlaid on an infrared image of other stars and galaxies. The infrared image was taken by ESO’s Visible and Infrared Survey Telescope for Astronomy (VISTA). Image credit: ALMA / ESO / NAOJ / NRAO / Rowland et al. / Dunlop et al. / CASU / CALET.
The galaxies we see today have come a long way from their chaotic, clumpy counterparts that astronomers typically observe in the early Universe.
These messy, early galaxies merge with each other and then evolve into smoother shapes at an incredibly slow pace.
Current theories suggest that, for a galaxy to be as orderly as our own Milky Way — a rotating disk with tidy structures like spiral arms — billions of years of evolution must have elapsed.
The detection of REBELS-25, however, challenges that timescale.
“According to our understanding of galaxy formation, we expect most early galaxies to be small and messy looking,” said Dr. Jacqueline Hodge, an astronomer at Leiden University.
In their study, Dr. Hodge and colleagues found that REBELS-25 resides at redshift z=7.3 (when the Universe was only 700 million years old), making it the most distant strongly rotating disk galaxy ever discovered.
“Seeing a galaxy with such similarities to our own Milky Way, that is strongly rotation-dominated, challenges our understanding of how quickly galaxies in the early Universe evolve into the orderly galaxies of today’s cosmos,” says Lucie Rowland, a doctoral student at Leiden University.
REBELS-25 was detected by the authors using the Atacama Large Millimeter/submillimeter Array (ALMA).
To properly discern the structure and motion of the galaxy, they performed follow-up observations with ALMA at a higher resolution, which confirmed its record-breaking nature.
Surprisingly, the data hinted at more developed features similar to those of the Milky Way, like a central elongated bar, and even spiral arms, although more observations will be needed to confirm this.
“Finding further evidence of more evolved structures would be an exciting discovery, as it would be the most distant galaxy with such structures observed to date,” Rowland said.
“These future observations of REBELS-25, alongside other discoveries of early rotating galaxies, will potentially transform our understanding of early galaxy formation, and the evolution of the Universe as a whole.”
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Lucie E. Rowland et al. REBELS-25: Discovery of a dynamically cold disc galaxy at z=7.31. MNRAS, published online October 7, 2024; doi: 10.1093/mnras/stae2217
Source : Breaking Science News