a lot better...we can excite these atoms in a lab and simply measure what comes out. often times don't even need a model because spectroscopy can be fully empirical for many transitions
And so you have proved my point. The observations presented in this article can be made consistent with both...as such one should think about stronger tests of both LCDM and MOND.
Again, LCDM and galaxy formation are two different things. "...and we didn't see what we were expecting at all..." It depends on who you ask. There were many pre-JWST models that did well in this regard. A particularly interesting one is this from 2018 (https://ui.adsabs.harvard.edu/abs/2018MNRAS.474.2352C/abstra...). That group even had to write another paper reminding everyone of what they predicted (https://ui.adsabs.harvard.edu/abs/2024arXiv240602672L/abstra...). Another example is here (https://ui.adsabs.harvard.edu/abs/2023OJAp....6E..47M/abstra...) which shows results from a simulation from ~2014. I can provide numerous other examples of this. My point isn't which theory is or isn't wrong, my point is that what is presented in this particular article is not a constraint on any realistic theory of gravity as the sensitivity of these particular observations to galaxy formation modeling is so strong.
This is a misrepresentation of what I am saying. By no means am I casting an aspersion on JWST. I am casting an aspersion on this particular observation as a test of MOND and LCDM. Also I highly disagree about your comments on my line of reasoning. The fact that you can obtain a huge range of possible galaxy properties in the context of LCDM indicates that in general, tests of LCDM and MOND that rely on galaxy formation model are in usually not strong tests. This is the key issue with using the abundance of high-z galaxies (or even their masses -- despite the fact that these aren't measured) as a test. In the context of LCDM, you need haloes to form galaxies but it has been shown many times that there are enough haloes to solve the problem (see the paper linked) by a huge amount.
In my opinion, this article is misleading at best. "...scans of ancient galaxies gathered by the JWST seem to contradict the commonly accepted predictions of the most widely accepted Cold Dark Matter theory, Lambda-CDM." --> LCDM doesn't predict what galaxies should look like, it simply predicts how much mass is in collapsed structures and that dark matter haloes grow hierarchically. In contrast, with JWST we see light and need to infer what the underlying properties of the system are. It was shown very early on that the theoretical upper limit (i.e. taking all of the gas that is available in collapsed structures and turning it into stars) predicts a luminosity function (i.e. number of galaxies per unit luminosity) that is orders of above what JWST has observed (e.g. https://ui.adsabs.harvard.edu/abs/2023MNRAS.521..497M/abstra...). This means that there is plenty of space within the context of LCDM to have bright and seemingly large and massive galaxies early on. Based on current JWST data at these early epochs, there are really no convincing arguments for or against LCDM because it's highly sensitive to the galaxy formation model that's adopted.
So I think it is fair to say they did exist. If we believe in Big Bang Nucleosynthesis then heavy elements had to come from somewhere making the first generation of stars (whatever their properties may be) be Population III. I agree that without a catalyst it's hard to initiate the CNO cycle but indeed models predict that it is possible even under these circumstances.
Multiple generations is perhaps an overstatement. The first oxygen in the Universe came from what we call Population III stars which is the first generation of stars to form after the Big Bang and what separates these from other stellar populations is that they do not have elements heavier than hydrogen or helium (except for minuscule traces left over from the Big Bang but these are insignificant). Now we don't know much about Population III stars but many models predict they are massive and when they die, can release 60 times the mass of our sun in the form of oxygen. That's really a lot of oxygen so you don't need too many of these to go off to pollute the early Universe and probably one of the reasons why we haven't yet found Population III stars.
I wouldn't say it's too damaging yet. There is a general trend where these early galaxies are brighter than we had thought by simply extrapolating models that were built prior to JWST, but these make numerous assumptions on how efficiently stars can form and the properties of these stars. Mildly relaxing any of these assumptions can easily solve the problem within our current framework and not significantly change what happens later in the evolution of the Universe.
It's a lot less sophisticated than that. They take images in multiple filters. In the context of JWST of order 10 filters (sometimes more sometimes less). Source extraction is then performed on the images by essentially identifying bright spots and dropping an aperture (separating ones that are nearby and blended if possible). The standard tool for this is called source extractor. They then have catalogs of tens of thousands of sources per image and the next step is to figure out redshift. There is a lot of code to do this but the simplest methods require fitting templates of what we think galaxies look like to these catalogs. High redshift sources tend to "drop" out of filters at shorter wavelengths. This is because neutral hydrogen in the early universe essentially absorbs almost all of the light at shorter wavelengths than 1216 angstroms. So if a galaxy is at redshift 10, the flux should essentially be zero at all filters that cover wavelengths shorter than 1.33 microns. JWST has filters both bluer and redder than this wavelength so we see the source appear in the redder filters and not the bluer ones. This technique was pioneered in the mid 1990s. This gives an approximate redshift called a "photometric redshift". There are other features in a galaxy spectrum that can mimic this "dropout" so not all photometric redshifts are robust. Therefore one has to take a spectrum of the galaxy which was what was done in this paper to confirm that the dropout is in fact the absorption feature we think it is. In this particular case, the authors were skeptical early on because there is a source right next to the object that is at a redshift where one of these other spectral features can mimic absorption by neutral hydrogen (this feature is the Balmer break). In any case, it's really an impressive demonstration of the power of JWST.