Ethan Siegel on JWST's Distant Galaxy Candidates

Ethan Siegel is worth reading today. (Well, he’s always worth reading. Did the most distant galaxy "candidates" survive JWST? - Big Think

In other words, the farther and farther back into the distant Universe we look, we have a picture of what we expect to see.

At some point, we should find the first and earliest bright, large, luminous galaxy, and we should see their number density rapidly decrease as we approach that limit.

Before that, we should find only smaller and less-evolved galaxies, decreasing in number and number density until we find the very first among those.

Before that, we should only see individual star clusters and proto-galaxies, and these should be extremely blue and primitive, and again should only exist in low number densities the farther back we go.

And finally, there should truly be a time where the very first stars and star clusters of all appear, and beyond that, there should be no luminous sources at all to observe, excepting the Big Bang’s leftover glow itself.

How is that essentially any different from what Jason Lisle said astronomers were expecting?

Seigel describes the impacts of CEERS + spectroscopy results:

The greatest impact that these results should have on the community is not for what the CEERS team/Edinburgh group did find, but what these findings point to.

Large, rich populations of galaxies and possibly even clusters and groups of galaxies exist in great numbers and potentially in high densities just ~1 billion years after the Big Bang, and perhaps even sooner.

There are a great many bright and evolved, heavy element-rich galaxies out there in the very early Universe: just 330-650 million years after the Big Bang. Many, and quite possibly most, of the “galaxy candidates” identified photometrically in that range will turn out to actually be at these great cosmic distances.

Very interestingly, these galaxies that we’re routinely finding in great numbers with JWST data would have absolutely shattered the cosmic record as recently as 9 months ago.

However, we haven’t yet found galaxies prior to ~300 million years of age in the Universe. They should be out there, although they may be smaller and fainter than the galaxies we’ve imaged so far.

We’re seeing how galaxies grow up during the early stages, and how they’re not falling into clean-and-neat categories like “this is a dusty, star-forming galaxy” or “this is a quasar,” but rather that they exhibit hybrid properties quite commonly early on.

And, perhaps most importantly, we’re finding these CEERS galaxies, photometrically, with a total of only one hour of JWST observing time for each galaxy. Just imagine what we can find with a true deep field: where days and days of observing time are devoted to imaging a single patch of sky.

For a start it’s what astronomers are still expecting, because the James Webb data doesn’t yet contradict it. It doesn’t say where “some point” is at all.

And don’t forget that the record is for observed galaxies - astronomers would expect the record to be broken by James Webb observations.

It’s different in that the article seems to claim at the end that so far the observations confirm the standard picture, and that they need spetroscopy on many more galaxies and probably a true “deep field” survey to truly test the predictions at the limits, whereas Jason Lisle says it’s already been disconfirmed.

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