Is there a stretching of the light curves of supernovae 1a?

[Line_112]

TL;DR Summary

I have doubts about the correctness of the results of the study of the slowing down of supernova explosions at high redshift.

The broadening of the light curves of distant supernovae is considered the most important argument in favor of the Big Bang theory and the Doppler effect. As I read, the authors of all studies of this kind are unanimous in the fact that the curves broaden with increasing redshift, and that this broadening is proportional to it. The latest, most extensive study is for 2024. But I have questions and assumptions about it.

The first question: what do the authors of this study mean by the length of the light curve? Judging by the graphs presented in that article, they study only a part of this curve, and, as written in the article itself, only the period after the maximum brightness was analyzed. In the graph of the exemplary curve of a type 1a flare, which I saw on the Internet, the length of the light curve should be at least 300 days after the maximum brightness. The authors' curve is cut off at about the 40th day after the maximum brightness. Therefore, I assumed that they examined only a piece of the curve - from the maximum brightness to the place of its bend, where it changes from a steep descent to a gentle one. Or a little further, to the place that was chosen by the authors at their own discretion.

The second point: if I understood everything correctly on the first question, then from the graphs of the light curves presented by the authors of the article (for different redshifts), there is no stretching of the curves there. The bend in the curve is approximately in the same place - on the 40th day from the point of maximum brightness of the supernova - for all three redshifts.

The third point: the authors combined the curves vertically so that the maximum brightness was the same for everyone (see top graph). But this will only happen with the Doppler effect and the like. With other effects, the brightness peak will most likely decrease with increasing Z. However, when combining the peaks, it is clear that the greater the red shift, the less clear the curve after the maximum brightness. The purple dots in the upper graph lie slightly above the red and orange, and the red ones are slightly above the orange. If we mentally shift the red and purple dots vertically downwards, then the brightness at the maximum brightness will be slightly lower, but in other areas the curves will coincide well with each other. This may probably mean that there is a mechanism for changing the light curves with increasing Z that is different from the Doppler, which reduces the maximum brightness, while increasing the brightness in other areas of the curve. In this case, the stretching of the light curves along the time scale is probably absent or insignificant in magnitude.

The authors are trying to adjust the curves to the Doppler effect, shifting them horizontally by the value of the red shift (see the bottom graph). In addition, when I carefully compared the upper and lower graphs, it turned out that the lower graph (that is, the one adjusted by the authors) has points that are not on the upper graph at all, but which make the picture below more convincing. Thus, it can be assumed that they determined the width of the light curves based on the adjustment of the curves to the expansion from the Doppler effect, plus I suspect manipulation of the data. Otherwise, there is no stretching there.

But I may be wrong, since I do not have all the information about this study.
What do you think about this?

Link to the study: https://lss.fnal.gov/archive/2024/pub/fermilab-pub-24-0293-ppd.pdf
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P.S. I apologize for the text published in Russian. This is the fault of the translator, who not only translated the text in the form to fill out on the forum, but also completely replaced it. I do not know why he did this. As a result, I sent the text in Russian, not in English.

 

[Ibix]

I think that in the graph you have reproduced the horizontal scaling is according to their equation (3), which depends on $\lambda_f$, which I believe is different for the three sets of points being plotted. So I suspect what you are seeing as "extra" points are actually the same red points, the same purple points, and the same yellow points, but moved with respect to points of other colours. I have to say the colour choices in that chart aren't particularly distinguishable, though, which doesn't help.

You could always ask the authors if they'd share the data for that chart - the corresponding author's email is at the bottom of the first page. If you do, though, I'd recommend against suggesting dishonesty on their part without a lot more evidence than eyeballing their chart.

 

[Line_112]

I think that in the graph you have reproduced the horizontal scaling is according to their equation (3), which depends on $\lambda_f$, which I believe is different for the three sets of points being plotted. So I suspect what you are seeing as "extra" points are actually the same red points, the same purple points, and the same yellow points, but moved with respect to points of other colours. I have to say the colour choices in that chart aren't particularly distinguishable, though, which doesn't help.

You could always ask the authors if they'd share the data for that chart - the corresponding author's email is at the bottom of the first page. If you do, though, I'd recommend against suggesting dishonesty on their part without a lot more evidence than eyeballing their chart.

Thank you for the constructive comment. When I compared the upper and lower graphs, I took into account that they shifted the dots by the redshift value. But, even in this case not everything matches up in terms of dots. Specifically, I noticed this in the right part of the graph with orange dots. But this is only an additional argument (I will not insist on it). More important is the analysis of the upper graph, where the correction is made only for brightness. This graph (comparison of the course of the curve formed by dots of different colors) visually agrees with the idea of the absence of stretching of the light curve with increasing redshift.
I would not contact the authors, since an outside assessment of those who understand this is important here. The authors will always insist on their rightness.

 

[Bandersnatch]

The first question

It's not that the length of the curve 'should be at least' 300 days. You can trace the brightness change over 300 days, or more, but when trying to compare how the curves differ in shape you only need a part of it - since they all have the same intrinsic shape. So you pick the part with the peak brightness, for two reasons: First, you can best see the stretching on the part that has the most verticality in it. That is to say, after the peak brightness the curve levels off, and it's hard to tell if data points tracing a nearly horizontal line are shifted horizontally w/r to another nearly horizontal line. Second, probably more important, you get best data from the peak brightness - because that's when the supernovae are actually best visible.
In yet another words: the cut off point is arbitrary, but it's where the most interesting things happen.

The second point

There is most certainly a stretching. As the authors say, it's immediately apparent. If you don't see it, then perhaps you're expecting more stretching than you should.
You're looking at data points with z~ = 0.21, =0.48, and =0.75. So, a reference point of a set flux, e.g. at around day 10 - roughly where the curve goes from concave to convex - should correspond to redshifted data points at around day 12, 15, and 17. Or, for the orange datapoints clustering around day 25, the red ones should cluster around 30, and the violet ones around 35. That's about what you can see with a naked eye. Of course the paper doesn't rely on naked eye analysis.
You can see a similar degree of stretch on the left side of the 0 point. The stretching direction is reversed there, because the curves are shifted by the authors to centre around the peak brightness (rather than having the 0 point at the initial flash moment, which would have all the stretching to the right).

The third point

The curves are normalised for flux - it even says so on the graphs. I.e. the difference in brightness that is expected from distant sources has been removed by the authors, as they tell you in the paper, to have the same peak brightness, so that they can compare the time scaling of the resultant curves.
That the differently coloured 'dots lie above' other dots is how the stretching shows. Because they don't lie above their corresponding dots, they are shifted horizontally from the day 0 axis.

What do you think about this?

I think the paper is fine.

 

[Line_112]

The curves are normalised for flux - it even says so on the graphs. I.e. the difference in brightness that is expected from distant sources has been removed by the authors, as they tell you in the paper, to have the same peak brightness, so that they can compare the time scaling of the resultant curves.
That the differently coloured 'dots lie above' other dots is how the stretching shows. Because they don't lie above their corresponding dots, they are shifted horizontally from the day 0 axis.

But then the supernova will become more and more energy-intensive with increasing Z, since the total volume of released energy is equal to the product of the luminosity and the flash time. That is, it will not be entirely correct. As if supernovae would have released more energy earlier than they do now. Therefore, I propose to lower the red and purple dots so that the peak brightness would be lower, and the brightness on the sides would be slightly higher. So that the total energy release of the supernovae would be the same. Then the curves agree well with each other and they no longer need to be shifted horizontally. But this is not even the main thing. The main thing is that the places of inflection of the curves along the time scale on the upper graph approximately coincide, indicating against the extension of the flash. This is especially noticeable by the bend on the 40th day from the maximum point. The first bend on the 20th day is not so clear due to the deficit of purple dots in that place and the orange dots protruding too much to the side. But if there is a difference, it is clearly less than it should be with such a difference in red shift. In addition, in the bend on the 40th day, it turns out the opposite, so the sum of the displacements is zero. At the same time, the bends become less clear with increasing Z, which is quite logical. In addition, this particular variant with a reduced peak and slightly raised sides will be obtained due to natural fluctuations in the movement of photons.

 

[Bandersnatch]

As if supernovae would have released more energy earlier than they do now.

They're constructing the reference curve by adjusting for expected observer artefacts: the dimming, and the widening. If you stop at an intermediate step, after correcting for one and before the other - which is what your complaint does - the curve won't resemble a rest-frame supernova. Luckily, the whole paper is concerned with correcting for the widening - including the other half of the figure you're focusing on.

The main thing is that the places of inflection of the curves along the time scale on the upper graph approximately coincide, indicating against the extension of the flash.

You're eyeballing a messy graph and try to build a far-reaching argument around it. All the while ignoring the rest of the paper that goes to great pains to extract clear trend lines from the data. The paper doesn't just say 'the curves sort of look wider, don't they?' That would be silly. The results of the analysis are shown in fig.7. What more is there to say?