Saturday, February 25, 2023

Webb telescope spots super old, massive galaxies that shouldn’t exist


Here we make use of the 1-5 μm coverage of the JWST early release observations to search for intrinsically red galaxies in the first ≈ 750 million years of cosmic history. In the survey area, we find six candidate massive galaxies (stellar mass > 1010 solar masses) at 7.4 ≤ z ≤ 9.1, 500–700 Myr after the Big Bang, including one galaxy with a possible stellar mass of ~1011 solar masses.

If verified with spectroscopy, the stellar mass density in massive galaxies would be much higher than anticipated from previous studies based on rest-frame ultraviolet-selected samples.

They posit two scenarios:

We infer that the possible interpretation of these JWST-identified “optical break galaxies” falls between two extremes. If the redshifts and fiducial masses are correct, then the mass density in the most massive galaxies would exceed the total previously estimated mass density...

The other extreme interpretation is that all the fiducial masses are larger than the true masses by factors of >10-100.

It will be extremely exciting to see if these mass density estimates are validated.

CU Boulder:

In a new study, an international team of astrophysicists has discovered several mysterious objects hiding in images from the James Webb Space Telescope: six potential galaxies that emerged so early in the universe’s history and are so massive they should not be possible under current cosmological theory.

“It’s bananas,” said Erica Nelson, co-author of the new research and assistant professor of astrophysics at CU Boulder. “You just don’t expect the early universe to be able to organize itself that quickly. These galaxies should not have had time to form.”

She explained that in astronomy, red light usually equals old light. The universe, Nelson said, has been expanding since the dawn of time. As it expands, galaxies and other celestial objects move farther apart, and the light they emit stretches out—think of it like the cosmic equivalent of saltwater taffy. The more the light stretches, the redder it looks to human instruments. (Light from objects coming closer to Earth, in contrast, looks bluer)...The team ran calculations and discovered that their old galaxies were also huge, harboring tens to hundreds of billions of sun-sized stars worth of mass, on par with the Milky Way.


While scanning a region of the cosmos near the Big Dipper, a group of astronomers identified six faint objects as they appeared well over 13 billion years ago. They suspect the objects are ancient galaxies. Scientists expect such early collections of stars and swirling matter to be relatively small. After all, such galaxies hadn't had much time to form or grow. But these galaxies are giants, the researchers report.

"If even one of these galaxies is real, it will push against the limits of our understanding of cosmology,” Nelson noted.


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