A Simple Direct Empirical Observation of Systematic Bias of the Redshift as a Distance Indicator

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

 

The paper describes an effort to shed light on the tension on Cosmology. More specifically the author is suggesting that the redshift determination may be biased due to the rotation velocity of the galaxies. The author claims that the rotation velocity of a galaxy is not fully understood and any anomaly may play a significant role on the determination of the redshift and thus to Cosmology.

The study has a important point to make and certainly deserves publication in my opinion. However, some statements should be down stated and the English in several parts need to be improved for the reader to understand and follow the line of arguments.

About the linear velocity compared with the rotational velocity, the author claims that the latter (the rotation) may be important and change the actual determination of the linear component. It has to be clearly stated that this is important in close by galaxies and not in the high redshift ones, where the linear velocity due to the Cosmology is expected to be high compared to the rotation. Thus, this analysis may affect samples for very low redshift as the study indicates.

 

Author Response

The paper describes an effort to shed light on the tension on Cosmology. More specifically the author is suggesting that the redshift determination may be biased due to the rotation velocity of the galaxies. The author claims that the rotation velocity of a galaxy is not fully understood and any anomaly may play a significant role on the determination of the redshift and thus to Cosmology.

--Author response: Thank you for reading and commenting on the manuscript. The replies to the comments is below.

 

The study has a important point to make and certainly deserves publication in my opinion. However, some statements should be down stated and the English in several parts need to be improved for the reader to understand and follow the line of arguments.

--Author response: Thank you for the comment. The writing has been improved in several parts. Many of the statements have also been changed as described below.

 

About the linear velocity compared with the rotational velocity, the author claims that the latter (the rotation) may be important and change the actual determination of the linear component. It has to be clearly stated that this is important in close by galaxies and not in the high redshift ones, where the linear velocity due to the Cosmology is expected to be high compared to the rotation. Thus, this analysis may affect samples for very low redshift as the study indicates.

--Author response: Thank you for the time you spent reading and reviewing the manuscript. Several changes were made, the language has been improved, and the paper is more clear and believed to be more pleasant to read. Also, you are definitely correct about the low redshift of the galaxies. When the redshift is lower, the rotational velocity is smaller relative to the linear velocity. That has been added to Section 5 (the new text in highlighted font). I also added to the same paragraph a proposed experiment to acquire a deep field by HST or JWST at around the galactic pole. I hope that in the future such experiment will be made, and until then it will be difficult to know how galaxies at higher redshifts are affected. The abstract also mentions that the galaxies in the experiment are limited to low redshift (z<0.25). A few other discussions and corrections have also been made.

 

 

Reviewer 2 Report

Comments and Suggestions for Authors

The observed asymmetry is interesting and difficult-to-explain theoretically, which makes it all that much more interesting.

However, the author has written papers with a related methodology, thesis and results many times, and it is unclear why yet another paper on the same topic is warranted.

Specifically, references 60-69 and 79-82 by the same author (some with collaborators) are mostly on this same subject. Why, at this point, is a related methodology, analysis of a related dataset, and results with a similar thesis important to the readers of Universe? I regret that I cannot see a significant reason after studying the paper, and doing multiple re-readings of the conclusions looking for the substantial break with prior analyses that warrants this new analysis. The small but non-zero asymmetry and its correlation with H0 is at this point mysterious. Why it should also correlate with our galaxy's north galactic pole is also mysterious. This paper does not seem to get us any closer to explaining this anomaly in the data.

Author Response

The observed asymmetry is interesting and difficult-to-explain theoretically, which makes it all that much more interesting.

--Author response: Thank you for the comments and for the time you spent reading and commenting on the manuscript. The replies to the comments are below each of the comments.

 

However, the author has written papers with a related methodology, thesis and results many times, and it is unclear why yet another paper on the same topic is warranted.

--Author response: The methodology indeed was used in the past, but the observation about the differences in the redshift is completely new. Previous papers focused on differences in the *brightness* of galaxies based on their direction of rotation relative to the Milky Way. This paper shows something different. It shows that the *redshift* of the galaxies that rotate in the same direction as the Milky Way is different from the redshift of galaxies spinning in the opposite direction. This is the first time that a link between redshift and rotational velocity of galaxies is shown. A new dataset was prepared for that, and it is released in this paper. That dataset includes galaxies with redshift, and was never used for any other experiment in the past. It is very possible that all of these observations are related to each other, but the observations are different aspects of galaxies. The link between the redshift and rotational velocity is an observation that is completely new, and is different from the link between rotational velocity and brightness as shown in previous papers. That observation has never been reported by me or by anyone else (that I am aware of).

 

Specifically, references 60-69 and 79-82 by the same author (some with collaborators) are mostly on this same subject. Why, at this point, is a related methodology, analysis of a related dataset, and results with a similar thesis important to the readers of Universe? I regret that I cannot see a significant reason after studying the paper, and doing multiple re-readings of the conclusions looking for the substantial break with prior analyses that warrants this new analysis. The small but non-zero asymmetry and its correlation with H0 is at this point mysterious. Why it should also correlate with our galaxy's north galactic pole is also mysterious. This paper does not seem to get us any closer to explaining this anomaly in the data.

 

--Author response: Thank you for the comment. As explained above, the previous papers are about link between the brightness of galaxies and their rotational velocity. This paper is the first ever to show a link between the redshift of a galaxy an its rotational velocity relative to the Milky Way. This is a new observation never been reported before.

I have to agree with you that the paper does not provide a proof to the observation, but mostly shows that such unexpected bias in the redshift exists. It is indeed a provocative observation that I believe will take time to fully understand. My hope is that by informing the community on its existence through this paper, other members of the community, especially theorists, will start examining it and propose explanations. That is why I also released the data, so others can look into it in ways I did not think of. In general, the physics of galaxy rotation is one of the most puzzling phenomena in nature. For instance, it has been at least five decades since the galaxy rotation curve anomaly was reported, and there is still no proven explanation to why that happens. But despite the absence of a proven explanation, the galaxy rotation curve is still important to study, and efforts are still being continued. I believe that the phenomenon reported in this paper will also justify the attention of theorists to explain it in the future. Also, redshift is the most common way to determine distances at cosmological scales, and any bias in that probe has an impact on cosmology. Section 5 has been revised (changes are in highlighted font) to make that point.

As for the Ho, that is now explained better in the paper. There is the H0 anisotropy, which is now explained in Section 5, and there is also the Ho tension. The Ho tension is explained briefly, but cites an experiment with the SH0ES dataset such that the galaxies were normalized by their spin direction relative to the Milky Way. The results show that when using just galaxies that rotate in the same direction as the Milky Way the H0 tension almost disappears, but that is done with a relatively small dataset of SH0ES. It is mentioned in the paper, but the details of the experiment itself are in the cited paper. That experiment was done in the past, and before the redshift bias was even noticed.

The correlation with the Northern galactic pole is due to the fact that the Milky Way rotates around its own pole. Therefore, galaxies that are on the galactic pole rotate in parallel to the Milky Way. Becaue they rotate in parallel to the Milky Way their rotational velocity can be compared to the Milky Way. Galaxies that rotate clockwise and are on the galactic pole rotate in the same direction relative to the Milky Way, and galaxies that rotate counterclockwise and are on the galactic pole rotate in the opposite direction relative to the Milky Way. That note has also been added to the paper to make the point more clear.

 

 

Reviewer 3 Report

Comments and Suggestions for Authors

This is an interesting paper doing important work that needs to be done to understand the assumed standard redshift measurements that are the basis for cosmological theories.

The data is well presented.

A few comments that would improve the paper/clarify.

1. Why is the discussion of the south pole data so much less complete/shorter than that of the north pole data?  Only one technique is applied to the south pole data while two were applied to the north pole data for instance.

2. Have the authors played at all with where they cut off the sample they consider clean enough to determine rotation to see effect of less stringent and more stringet cuts?

3. The conclusion rambles too much and contains what would be considered interpretation as opposed to conclusions. Some of this interpretation isn't particularly well explored.  I would recommend creating a separate interpretation section and being careful what to include and what not in there so it is robust. Focusing on models which could explain the rotation associated modulation is what I would recommend. That is it fascinating that we don't have a good explanation for how so large n effect could exist in actuality do we? Are there models which fit this - that is where the interpretaiton should focus.

4. the conclusion I think should focus on the need to examine redshifts as a distnce indicator and what systemtaic effects might exist such as rotation.  

5. there are minor English corrections tht a reread might improve - they are few however.

Comments on the Quality of English Language

The Engliash quality is good with only  few repeated words here and there. So a simple reread can find them. But they are few and the English is good.

Author Response

This is an interesting paper doing important work that needs to be done to understand the assumed standard redshift measurements that are the basis for cosmological theories.

The data is well presented.

 

--Author response: Thank you for reading and commenting on the manuscript, and for the kind words. The replies to your comments are below, with the description of the changes made to the manuscript. Changes made to the manuscript are highlighted with bold font.

 

A few comments that would improve the paper/clarify.

 

1. Why is the discussion of the south pole data so much less complete/shorter than that of the north pole data?  Only one technique is applied to the south pole data while two were applied to the north pole data for instance.

 

--Author response: Thank you for the comment. First of all, Ganalyzer provides much cleaner data compared to the other methods. That has been added to Section 4. All datasets are available, so the reader can make their own impression and examine the accuracy of the analysis of each dataset. As discussed in Section 4.2, the error rate of sparcfire is ~15%, which is pretty high, while the Ganalyzer dataset is clean. That is an important reason to use Ganalyzer, while sparcfire was used as a highly secondary analysis, and cannot provide a proof unless better annotation is used. Also, Galaxy Zoo annotations are not available for the DESI Legacy Survey, and because they take years of manual annotations it is not practical to have them. That note has also been added to Section 4.  

But the reasons that the Southern data is not highlighted as much as the Northern data is not just the availability of different types of annotations, but also the sources of the redshift. The North pole data has redshifts all taken from the same source, and the same instrument (SDSS). The redshifts for the Southern pole were taken from SIMBAD, and therefore taken from a collection of sources, each source uses a different instrument. That makes it somewhat less sound, although it is unlikely that different sources of redshift would lead to something like this. That has been added to Section 4 (highlighted font).

 

2. Have the authors played at all with where they cut off the sample they consider clean enough to determine rotation to see effect of less stringent and more stringet cuts?

 

--Author response: Yes. That was done in the end of Section 4.2. The dataset generated by Ganalyzer is clean, so error was added intentionally. The results show that the delta z gets smaller when the error is higher. That is explained in the end of Section 4.2.

 

3. The conclusion rambles too much and contains what would be considered interpretation as opposed to conclusions. Some of this interpretation isn't particularly well explored.  I would recommend creating a separate interpretation section and being careful what to include and what not in there so it is robust. Focusing on models which could explain the rotation associated modulation is what I would recommend. That is it fascinating that we don't have a good explanation for how so large n effect could exist in actuality do we? Are there models which fit this - that is where the interpretaiton should focus.

--Author response: Substantial changes have been made to address the comment. A new section titled “Possible explanations and future experiments” has been added. That section discusses the possible explanations and other related discussions. It is clear that there is no immediate explanation to the observation. But the physics of galaxy rotation is still a mystery, even after decades of research since the galaxy rotation curve anomaly was discovered. That is also discussed in that section. The understanding of the physics of galaxy rotation is still an on-going research topic, as it has been for the past five decades, but the observation reported here might provide another piece of the puzzle. It is hopeful that members of the community, especially the theorists, will be able to come up with ideas to explain it or relate it to other observations in physics and cosmology. The paper is now somewhat long (nearly 8000 words), but probably still within reasonable length.

 

4. the conclusion I think should focus on the need to examine redshifts as a distnce indicator and what systemtaic effects might exist such as rotation.  

--Author response: Thank you for the comment. That has been added to the Section 5 (in highlighted font). Also, the conclusion section now includes a brief description of a proposed experiment to study the observation at high redshifts (by deep fields covering the galactic pole using JWST or HST).

 

5. there are minor English corrections tht a reread might improve - they are few however.

--Author response: The manuscript has been read carefully. You are correct that some typos and grammar errors were present, and they were corrected.

 

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The revisions make the significance of the puzzle more poignant. It is certainly a provocative result. Time will tell whether it stands up to larger datasets or other scrutiny, but the result can and should be published in its current form. 

My only quibble in the revised text would be to recommend removing the sentence at line 390, "It is therefore possible that the mysterious physics of galaxy rotation affects the light emitted by galaxies in a way that is not proportionate to their rotation velocity."

I recommend this simply because "affects the light emitted" seems to me to be too broad and vague and therefore doesn't help me understand the overall puzzle and significance.

Whether to keep, delete, or revise this sentence is the author's discretion. The paper can be accepted with or without any change at line 390.