[astroH]

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.

[ajross]

> there are really no convincing arguments for or against LCDM because it's highly sensitive to the galaxy formation model that's adopted.

To be fair, that is absolutely not the way ΛCDM would have been described to someone in the pre-Webb days. It was a well-regarded theory and the hope was (a-la the Higgs detection) that new data would just better constrain the edges and get us on to the next phase of the problem.

But instead it's a wreck, and we didn't see what we were expecting at all, and so now we're retreating to "Well, ΛCDM wasn't exactly proven wrong, was it?!"

That doesn't mean it's wrong either, and it for sure doesn't mean MOND is right. But equally for sure this is a Kuhnian paradigm shift moment and I think it's important for the community to be willing to step back and entertain broader ideas.

[astroH]

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.

[Davidzheng]

Absolutely not in the field, so if you are please completely disregard. But from conversations with physicists (not cosmologists) I always thought people thought a lot of evidence for ΛCDM was dubious at best.

[uoaei]

> with JWST we see light and need to infer what the underlying properties of the system are

Every theory of dark matter is based exclusively on light-emitting objects. There is no "contrast" between JWST's methods and those of others. Casting aspersions on JWST because it can only see light is like casting aspersions on Galileo because he could only build telescopes. If we could teleport to the things we study and get more information that way, it would be nice, but we live in reality and must bend to its rules.

> highly sensitive to the galaxy formation model that's adopted

I should only need to remind the reader of the classic idiom "cart before the horse" to remind them that this line of reasoning is invalid.

[astroH]

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.

[MattPalmer1086]

You are missing the point. JWST is not being singled out as different here, and no aspersions are being cast.

It is the entirely general point that all we can observe is the light, and we have to infer what that means. Maybe things are bright because there's a lot of stars. Maybe there aren't but there is not much dust. Maybe there aren't so many stars but they are bigger and brighter. There is room to fit many different models on the basis of the light that is observed.