The formation of galaxies by gradual hierarchical co-assembly of baryons and cold dark matter halos is a fundamental paradigm underpinning modern astrophysics and predicts a strong decline in the number of massive galaxies at early cosmic times. Extremely massive quiescent galaxies have been observed as early as 1-2 billions years after the Big Bang. These are extremely constraining on theoretical models as they form 300 to 500 million years earlier and only some models can form massive galaxies this early. The spectrum of the newly-discovered quiescent galaxy ZF-UDS-7329 reveals features typical of much older stellar populations. Detailed modeling shows the stellar population formed around 1.5 billion years earlier in time at an epoch when dark matter halos of sufficient hosting mass have not yet assembled in the standard scenario. This observation may point to the presence of undetected populations of early galaxies and the possibility of significant gaps in our understanding of early stellar populations, galaxy formation and/or the nature of dark matter.
The formation of galaxies is a fundamental paradigm underpinning modern astrophysics and predicts a strong decline in the number of massive galaxies in early cosmic times.
Extremely massive quiescent galaxies have now been observed as early as 1-2 billion years after the Big Bang which challenges previous theoretical models.
“We’ve been chasing this particular galaxy for seven years and spent hours observing it with the two largest telescopes on earth to figure out how old it was,” said Swinburne University of Technology’s Professor Karl Glazebrook.
“But it was too red and too faint, and we couldn’t measure it. In the end, we had to go off earth and use Webb to confirm its nature.”
“This was very much a team effort, from the infrared sky surveys we started in 2010 that led to us identifying this galaxy as unusual, to our many hours on the Keck and Very Large Telescope where we tried, but…
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