I Observational evidence against expanding universe in MNRAS

[Jean Tate]

If one does not have a workable answer to my second question above (actually a two-parter), how could you go about obtaining that data yourself?

Start with L14, the paper. The references in fact.

There are 16, and ADS can help you get at least the titles, abstracts, etc (the actual papers may be behind paywalls). Of these 16, I think two may be relevant for the HUDF data (10. Beckwith S. V. W., Stiavelli M., Koekemoer A. M., et al., ApJ 132, (2006) 1729, and 11. Coe D., Bentez N. Snchez S. F., Jee M., Bouwens R., Ford H., AJ 132, (2006) 926), but none appear relevant for the GALEX data. Do you agree?

Hmm, so maybe the paper itself gives a pointer to the GALEX data?

"... all GALEX MIS3-SDSSDR5 galaxies ..."

What do you think? Can you use that to find where the L14 GALEX data comes from? To actually obtain that data?

 

[elerner]

Hi all, I have been busy with other things so have not visited here for the past few days.
In more or less chronological order:

Peter, (1+z)^-3 is correct if we measure in AB magnitudes (per unit frequency). This is the unit the papers use.

Ruarimac:

This is a test of predictions—things written before data is taken. Predictions are crucial in science. If you can’t predict data before you observe it, then you are not doing useful science. Just fitting the data once you have it is useless unless you can use it to predict lots more data that you have not observed. As the saying goes, with 4 variables, I can fit an elephant. That is why I used predictions from before the data was available. In addition, any merger process is contradicted by the observations of the number of mergers and any growth needed to match the data is contradicted by the measurements of gravitational mass vs stellar mass—unless you want to hypothesize negative mass dark matter (as I’m sure someone will do.)

Jonathan Scott:

Tolman’s derivation does not depend on curvature. You can find it in many places in the literature since 1930. It only depends on expansion.

On GALEX, measurement, etc.

Selfsim—you did not read my comment that my measured resolution refers to radius while FWHM refers to diameter. The key point is that with both Hubble and GALEX the resolution is mainly linked to the pixel size. That is why it is not linked to the wavelength—the pixel size does not change with wavelength.

Jean Tate: Not just the point at 0.027 but all the low z points up to z=0.11 are used for comparisons with our 2014 data. The whole point of the Tolman test is to compare sizes as we measure them at low z, where there is no cosmic distortion, with those at high z (or comparing SB of the same luminosity galaxies, which is the same as measuring size). So you can’t drop the near points if you want to do the test. The reason we can measure tiny galaxies is that when we talk about radius, that is half-light radius, the radius that contains half the light. Since disk galaxy light falls off exponentially, you can observe these bright galaxies way out beyond their half light radius and thus you can get very nice fits to an exponential line. The Sersic number is used as a cutoff between disk galaxies and ellipticals. AGNs don’t interfere as we dropped the central area of the galaxy which is most affected by the PSF blurring. The exponential fit starts further out—all explained in the 2014 paper. By the way, I don’t think checking our measurements is all that useful as we already checked them against the GALEX catalog, and they are quite close. But we wanted to make sure we were measuring HUDF and GALEX the exact same way.

Sure I can put our old 2014 data up somewhere. It would be great to have others work on it. Where would you suggest? However, it is by no means the most recent data release. I can also post how to get the more recent data. But not tonight.

 

[PeterDonis]

Peter, (1+z)^-3 is correct if we measure in AB magnitudes (per unit frequency).

Ok, got it.

 

[SelfSim]

... Selfsim—you did not read my comment that my measured resolution refers to radius while FWHM refers to diameter. The key point is that with both Hubble and GALEX the resolution is mainly linked to the pixel size. That is why it is not linked to the wavelength—the pixel size does not change with wavelength.

Eric - Thanks for your reply.

However, as described by the Rayleigh criterion, (θ = 1.220λ/D), where the resolution is decreased by filter choice, more light ends up falling onto adjacent pixels which then affects the radius (or diameter) of the FHWM (or ensquared energy value).

In an attempt to put the resolution vs filter issue to rest, in the interim, we've performed a small test of our own by downloading some f475w and f814w filtered data for the object Messier 30 from the Hubble legacy archive site.

The ACS was used but unlike the HUDF images an 814W filter was used instead of the 850LP.

Unlike our previous discussion where only the optics were considered, the system angular resolution which links both wavelength and pixel size is defined by the equation.

System angular resolution ≈ [(0.21λ/2.4)² + (0.05²)]º̇⁵

The 0.05 term is the size of the ACS pixels in arcsec.
For a 475W filter the theoretical resolution is 0.066 arcsec and the 814W filter is 0.087 arcsec.

For the Messier 30 data, the same six stars of medium brightness were handpicked for each filter so as not to distort the FWHM measurements. (AIP4WIN software was used for the measurements).

In all cases, the FWHM of the stars were higher in the 814W data, the results being:

475W data FWHM = 0.279 +/- 0.035
814W data FWHM = 0.326 +/- 0.058

A larger sample size would have been preferable but the dependence of resolution on wavelength is clearly evident.

Irrespective of what method you employ, a lack of differentiation of resolution between the Hubble filtered data, is telling.

 

[ruarimac]

This is a test of predictions—things written before data is taken. Predictions are crucial in science. If you can’t predict data before you observe it, then you are not doing useful science. Just fitting the data once you have it is useless unless you can use it to predict lots more data that you have not observed. As the saying goes, with 4 variables, I can fit an elephant. That is why I used predictions from before the data was available. In addition, any merger process is contradicted by the observations of the number of mergers and any growth needed to match the data is contradicted by the measurements of gravitational mass vs stellar mass—unless you want to hypothesize negative mass dark matter (as I’m sure someone will do.)

You're just making broad statements without actually addressing the points. I never mentioned fitting, please do not misrepresent my words.

You have tested a very specific model of disk size evolution combined with cosmology, but you are selling this as evidence against cosmology specifically when you haven't demonstrated that. You believe it's not mergers but that's hardly the only thing absent from this model. Take for example the fact that this model is not modelling the UV sizes which you are comparing it to. Or the fact that you haven't tested the effect of your cuts to the data, you will have selection effects which will change with redshift due to using different bands. Or the fact you haven't made K corrections due to the fact that the different filters have different transmission curves. Or the fact that in applying this model to UV surface brightness you don't take into account the varying star formation rate density with time in an expanding universe, as observed. Or the fact you have to assume the Tully-Fisher relation is fixed up to z~5 and that it applies to all of your galaxies. And then there's the effect of mergers and blending.

As I said before you have tested a single model which has all of these shortcomings, you do not justify why this is the model above all others that should be correct. This was not the only model available. You haven't demonstrated that this mismatch is a problem with cosmology and not with your attempt to model the observations. You haven't convinced me this is a problem with cosmology given that requires relying on a single model and a shopping-list of assumptions.

 

[Jean Tate]

Thanks for your reply and continued interest in your paper, elerner!

Hi all, I have been busy with other things so have not visited here for the past few days.
In more or less chronological order:

<snip>

On GALEX, measurement, etc.

<snip>

Jean Tate: Not just the point at 0.027 but all the low z points up to z=0.11 are used for comparisons with our 2014 data. The whole point of the Tolman test is to compare sizes as we measure them at low z, where there is no cosmic distortion, with those at high z (or comparing SB of the same luminosity galaxies, which is the same as measuring size). So you can’t drop the near points if you want to do the test. The reason we can measure tiny galaxies is that when we talk about radius, that is half-light radius, the radius that contains half the light. Since disk galaxy light falls off exponentially, you can observe these bright galaxies way out beyond their half light radius and thus you can get very nice fits to an exponential line. The Sersic number is used as a cutoff between disk galaxies and ellipticals. AGNs don’t interfere as we dropped the central area of the galaxy which is most affected by the PSF blurring. The exponential fit starts further out—all explained in the 2014 paper. By the way, I don’t think checking our measurements is all that useful as we already checked them against the GALEX catalog, and they are quite close. But we wanted to make sure we were measuring HUDF and GALEX the exact same way.

Sure I can put our old 2014 data up somewhere. It would be great to have others work on it. Where would you suggest? However, it is by no means the most recent data release. I can also post how to get the more recent data. But not tonight.

I have many, many questions. Some come from my initial reading of Lerner (2018) (L18); some from your latest post. I will, however, focus on just a few.

So you can’t drop the near points if you want to do the test.

My primary interest was, and continues to be, Lerner+ (2014) (L14). However, I see that you may have misunderstood what I wrote; so let me try to be clearer.

I "get" that Lerner (2018) (L18) must include some low z data. And I think I'm correct in saying that L18 relies critically on the robustness and accuracy of the results reported in L14. In particular, the "the GALEX point at z=0.027 from Lerner, Scarpa and Falomo,2014". Does anyone disagree?

It makes little difference if that GALEX point is at z=0, or z=0.11, or anywhere in between. Does anyone disagree?

However, it makes a huge difference if that GALEX point is not near Log (r/kpc) =~0.8.

I am very interested in understanding just how robust that ~0.8 value is. Based on L14.

AGNs don’t interfere as we dropped the central area of the galaxy which is most affected by the PSF blurring. The exponential fit starts further out—all explained in the 2014 paper.

Actually, no. It is not all so explained.

I've just re-read L14; a) AGNs are not mentioned, and b) there's no mention of dropping the central area for galaxies which are smaller than ~10" ("PSF blurring" is almost certainly important out to ~twice the PSF width).

There are two questions in my first post in this thread which you did not answer, elerner; perhaps you missed them?

Here they are again:

JT1) In L14, you wrote: "For the GALEX sample, we measured radial brightness profiles and fitted them with a Sersic law, [...]".
Would you please describe how you did this? I'm particularly interested in the details of how you did this for GALEX galaxies which are smaller than ~10" (i.e. less than ~twice the resolution or PSF width).

JT2) In L14, you wrote: "Finally we restricted the samples to disk galaxies with Sersic number <2.5 so that radii could be measured accurately by measuring the slope of the exponential decline of SB within each galaxy."
I do not understand this. Would you please explain what it means?

Sure I can put our old 2014 data up somewhere. It would be great to have others work on it. Where would you suggest?

I've already made one suggestion (GitHub); perhaps others have other suggestions?

By the way, when I tried to access L18 (the full paper, not the abstract) from the link in the OP, I got this message:

"You do not currently have access to this article."

And I was invited to "Register" to get "short-term access" ("24 Hours access"), which would cost me USD $33.00. So instead I'm relying on the v2 arXiv document (link). Curiously, v2 was "last revised 2 Apr 2018", but "Journal reference: Monthly Notices of the Royal Astronomical Society, sty728 (March 22, 2018)". Could you explain please elerner?

 

[Jean Tate]

You're just making broad statements without actually addressing the points. I never mentioned fitting, please do not misrepresent my words.

You have tested a very specific model of disk size evolution combined with cosmology, but you are selling this as evidence against cosmology specifically when you haven't demonstrated that. You believe it's not mergers but that's hardly the only thing absent from this model. Take for example the fact that this model is not modelling the UV sizes which you are comparing it to. Or the fact that you haven't tested the effect of your cuts to the data, you will have selection effects which will change with redshift due to using different bands. Or the fact you haven't made K corrections due to the fact that the different filters have different transmission curves. Or the fact that in applying this model to UV surface brightness you don't take into account the varying star formation rate density with time in an expanding universe, as observed. Or the fact you have to assume the Tully-Fisher relation is fixed up to z~5 and that it applies to all of your galaxies. And then there's the effect of mergers and blending.

As I said before you have tested a single model which has all of these shortcomings, you do not justify why this is the model above all others that should be correct. This was not the only model available. You haven't demonstrated that this mismatch is a problem with cosmology and not with your attempt to model the observations. You haven't convinced me this is a problem with cosmology given that requires relying on a single model and a shopping-list of assumptions.

(my bold)

L14 seems replete with such assumptions.

Both explicitly stated and not. Such as some concerning AGNs, one aspect of which I addressed in my last post:

AGNs don’t interfere as we dropped the central area of the galaxy which is most affected by the PSF blurring. The exponential fit starts further out—all explained in the 2014 paper.

Actually, no. It is not all so explained.

I've just re-read L14; a) AGNs are not mentioned, [...]

Reminder; here's what's in L14:

These UV data have the important advantage of being sensitive only to emissions from very young stars.

In his last post here, elerner seems to have hinted at another, unstated assumption:

The Sersic number is used as a cutoff between disk galaxies and ellipticals.

The implication (not even hinted at in L14) is that the only galaxy morphological classes are "disk galaxies" and "ellipticals". Or at least, only those two in the UV. The L14 authors seem to have been unaware of the extensive literature on this topic ...

 

[elerner]

Hard for me to keep up with all of you in the time available. Simple things first. The new version corrects a reference and will soon be posted on MNRAS as well. If you missed the free download, go to our website https://lppfusion.com/lppfusion-chi...-against-cosmic-expansion-in-leading-journal/ and click on “paper” to get a free copy. I can’t post the link directly without violating their rules.

Here is how we did the measurements in 2014:

To measure total flux and half light radius, we extracted the average surface brightness profile for each galaxy from the HUDF or GALEX images. The apparent magnitude of each galaxy is determined by measuring the total flux within a fixed circular aperture large enough to accommodate the largest galaxies, but small enough to avoid contamination from other sources. To choose the best aperture over which to extract the radial profile, for each sample we compared average magnitudes and average radii as derived for a set of increasingly large apertures. We then defined the best aperture as the smallest for which average values converged. We found that these measurements are practically insensitive to the chosen aperture above this minimum value.

Finally, to determine scale-length radius, we fitted the radial brightness profile with a disk law excluding the central 0.1 arcsec for HST and 5 arcsec for GALEX , which could be affected by the PSF smearing. Given the magnitude and radius, the SB is obtained via the formulae in Section 2. A direct comparison between our measurements and those in the i band HUDF catalogue (Coe et al 2006) show no significant overall differences.

Here is how we checked for non-disks:

Finally we have checked, by visual inspection of galaxies in the sample, that removing objects exhibiting signatures of interaction or merging do not change our conclusions. The selection of galaxies with disturbed morphology was performed by an external team of nine amateur astronomers evaluating the NUV images and isophote contours of all NUV-sample galaxies. Each volunteer examined the galaxies and only those considered unperturbed by more than 5 people were included in a “gold” sample. Although this procedure reduces the size of the sample, there is no significant difference of the SB-z trend.

 

[Jean Tate]

Haven't heard from any PF Mods yet, and it seems that there's rather a lack of interest in my proposal (to independently try to verify the GALEX results reported in L14). So this will likely be my last post on that (my proposal).

If one does not have a workable answer to my second question above (actually a two-parter), how could you go about obtaining that data yourself?

Start with L14, the paper. The references in fact.

There are 16, and ADS can help you get at least the titles, abstracts, etc (the actual papers may be behind paywalls). Of these 16, I think two may be relevant for the HUDF data (10. Beckwith S. V. W., Stiavelli M., Koekemoer A. M., et al., ApJ 132, (2006) 1729, and 11. Coe D., Bentez N. Snchez S. F., Jee M., Bouwens R., Ford H., AJ 132, (2006) 926), but none appear relevant for the GALEX data. Do you agree?

Hmm, so maybe the paper itself gives a pointer to the GALEX data?

"... all GALEX MIS3-SDSSDR5 galaxies ..."

What do you think? Can you use that to find where the L14 GALEX data comes from? To actually obtain that data?

"SDSS" is likely well-known to most readers; it refers to the Sloan Digital Sky Survey, and images from it were used in the hugely successful online citizen science project, Galaxy Zoo (there are quite a few iterations of Galaxy Zoo, using images/data from several surveys other than SDSS, but not GALEX as far as I know).

"DR5" means Data Release 5.

I did not know what "MIS3" meant (maybe I did, once, but forgot); however, it's fairly easy to work out using your fave search (mine is DuckDuckGo) ... "MIS" is Medium Depth Imaging Survey, and "3" likely refers to GALEX DR3.

Both SDSS and GALEX have official websites, and from those it's pretty straight-forward to find out how to access the many data products from those surveys.

Rather than doing that, I'd like to introduce a resource which you may not know about, VizieR. If you enter "GALEX" in the "Find catalogues" box, the first (of four) hits you'll see is "II/312", "GALEX-DR5 (GR5) sources from AIS and MIS (Bianchi+ 2011)", and you have several "Access" choices. True, it's not the GALEX MIS3, but is surely a superset.

 

[Jean Tate]

Thank you, elerner.

Hard for me to keep up with all of you in the time available. Simple things first. The new version corrects a reference and will soon be posted on MNRAS as well. If you missed the free download, go to our website https://lppfusion.com/lppfusion-chi...-against-cosmic-expansion-in-leading-journal/ and click on “paper” to get a free copy. I can’t post the link directly without violating their rules.

Here is how we did the measurements in 2014:

To measure total flux and half light radius, we extracted the average surface brightness profile for each galaxy from the HUDF or GALEX images. The apparent magnitude of each galaxy is determined by measuring the total flux within a fixed circular aperture large enough to accommodate the largest galaxies, but small enough to avoid contamination from other sources. To choose the best aperture over which to extract the radial profile, for each sample we compared average magnitudes and average radii as derived for a set of increasingly large apertures. We then defined the best aperture as the smallest for which average values converged. We found that these measurements are practically insensitive to the chosen aperture above this minimum value.

Finally, to determine scale-length radius, we fitted the radial brightness profile with a disk law excluding the central 0.1 arcsec for HST and 5 arcsec for GALEX , which could be affected by the PSF smearing. Given the magnitude and radius, the SB is obtained via the formulae in Section 2. A direct comparison between our measurements and those in the i band HUDF catalogue (Coe et al 2006) show no significant overall differences.

Here is how we checked for non-disks:

Finally we have checked, by visual inspection of galaxies in the sample, that removing objects exhibiting signatures of interaction or merging do not change our conclusions. The selection of galaxies with disturbed morphology was performed by an external team of nine amateur astronomers evaluating the NUV images and isophote contours of all NUV-sample galaxies. Each volunteer examined the galaxies and only those considered unperturbed by more than 5 people were included in a “gold” sample. Although this procedure reduces the size of the sample, there is no significant difference of the SB-z trend.

It'll take me a while to fully digest this, particularly as I want to understand it in terms of the content of L14.

However, I'm even more curious about how you "fitted the radial brightness profile with a disk law excluding the central 0.1 arcsec for HST and 5 arcsec for GALEX".

For example, did you write your own code? Or use a publicly available tool or package? Something else??

 

[PeterDonis]

Thread closed for moderation.

 

[PeterDonis]

The thread is being reopened in order to allow continued discussion of the specific paper referenced in the OP, and to allow @elerner to respond to specific questions regarding that paper (and the 2014 paper that it is based on). Please limit discussion to that specific topic. This thread is not about the general methodology of science or the overall pros and cons of the current mainstream cosmological model of the universe.

@elerner, in responding to questions, please give specific cites to your papers rather than general claims and opinions. We understand your basic claims; we are looking for the specific evidence and arguments given in your papers that you think support those claims, not repetitions of the claims themselves. Additional fine details of methodology not provided in the papers are fine (since that is a large part of what other posters have asked about).

 

[PeterDonis]

it seems that there's rather a lack of interest in my proposal (to independently try to verify the GALEX results reported in L14)

This is outside the scope of PF. Independent replication of scientific results is original research, which is not what PF is for.

 

[PeterDonis]

There are a range of sophisticated galaxy formation simulations available today, they would be a much better comparison given they represent the leading edge of the field and that the selection function could be applied to them.

@elerner, this is one question that I did not see you respond to. Is there a reason why the particular model of galaxy size evolution used in the paper was chosen? Or is there further work planned to apply a similar methodology to a wider range of models of galaxy size evolution?

 

[PeterDonis]

sizes as we measure them at low z, where there is no cosmic distortion

Doesn't this contradict your claim that the "expansion hypothesis" applies at all scales, right down to $z = 0$?

 

[elerner]

ruarimac said: ↑ There are a range of sophisticated galaxy formation simulations available today, they would be a much better comparison given they represent the leading edge of the field and that the selection function could be applied to them.

@elerner, this is one question that I did not see you respond to. Is there a reason why the particular model of galaxy size evolution used in the paper was chosen? Or is there further work planned to apply a similar methodology to a wider range of models of galaxy size evolution?

I did reply to this, but I can elaborate. My goal was to test the predictions based on the expansion hypothesis against the galaxy size and related data sets. For disk galaxies, the dominant , in fact only, theory I could find that made predictions prior to the publication of the data sets (starting around 2005) was the Mo et al theory. This is also the one that is by far most referenced as a comparison in the literature.

The many more recent simulations of galaxy growth do not produce predictions that can be tested against this data set. The models contain many free parameters that, the authors describe, are adjusted to fit the available data, including data on galaxy size and growth. As I pointed out in a previous post, fits to a data set can’t be tested against that data set. They can be tested only against new, different data sets that don’t exist at the time that the fits are made.

For ellipticals, I looked at predictions made not only by Mo et al, but also by three different theories of elliptical galaxy growth: puffing up, major merger and minor mergers. These are all I found referenced. My paper shows in detail that these theories also make quantitative predictions that conflict with observations, such as merger rates and the velocity dispersions of high-z ellipticals. This last data set poses a particularly severe conflict as it implies that for any expanding universe model the gravitating mass of high-z ellipticals is less than their stellar mass.

 

[elerner]

sizes as we measure them at low z, where there is no cosmic distortion
Doesn't this contradict your claim that the "expansion hypothesis" applies at all scales, right down to z=0" role="presentation">z=0?

Clearly not, as the formula for distortion depends on 1+z. When 1+z differs only slightly from 1, the cosmic distortion is insignificant. Strictly speaking, "no cosmic distortion" is a misstatement. I meant "no significant distortion" . Also, I don't say that expansion makes predictions down to z=0--i.e. the room next to yours. It makes predictions for all scales where matter is not bound gravitationally. This is thus for scales more than a few Mpc. That definition of "small scale" is far smaller than the 200-800 Mpc scale measurements that are the low-z comparisons in my paper.

 

[ruarimac]

The many more recent simulations of galaxy growth do not produce predictions that can be tested against this data set. The models contain many free parameters that, the authors describe, are adjusted to fit the available data, including data on galaxy size and growth.As I pointed out in a previous post, fits to a data set can’t be tested against that data set. They can be tested only against new, different data sets that don’t exist at the time that the fits are made.

The fact that a model was published after HUDF does not mean it was calibrated to it your observations, that is simply false. As a counter example I can point to the EAGLE simulations which are calibrated to the z~0 stellar mass-size relation from GAMA and SDSS. It was not calibrated on the redshift evolution and yet it matches data very well in size evolution from CANDELS which it was not calibrated to, nor UDF for that matter.

http://adsabs.harvard.edu/abs/2017MNRAS.465..722F

The calibration is described here:

https://arxiv.org/abs/1407.7040

It simply isn't true that this is the only model available. I do recommend you compare to a simulation in future, at the very least they can test the systematics of your analysis.

Furthermore your argument is illogical. You said you don't want to compare recent models with your data because they're fit to this data (which is false). But your claims about cosmology rest on the claim that there is no way to fit the data in an expanding universe. But then it doesn't matter if the galaxy evolution model was fit to the data, the parameters still have to be physical. If a fitted physical model can match the data then the data can be explained in an expanding universe, your whole argument about this being a problem for cosmology falls apart. I'm afraid you can't make both arguments simultaneously.

 

[laymanB]

If this hypothesis was correct and the universe is not expanding, is eternal, and is evolving as a function of time, why would not all the stars have burned out an infinite time ago?

 

[elerner]

If a fitted model can match the data then the data is can be explained in an expanding universe, your whole argument about this being a problem for cosmology falls apart. You can't make both arguments simultaneously.

Of course I can. It concerns different sets of data that still relate to the same size question. If you have just the disk size data, you can certainly fit it ex post facto with sufficient numbers of free variables. But for the ellipticals, the merger theories also make predictions about the rate of mergers, which can be tested against merger observations. In addition any size evolution for the ellipticals that matches the data also produces the paradox from the velocity data that the implied gravitational mass is less than the stellar mass. So for ellipticals you can't fit the size data, the merger data and the velocity data no matter what you do.

In the case you cited of Eagle, they claim a good fit to van der Wels. But in section 7 of my paper, I show why van der Wel's disk data disagrees with both Shibuya and Lerner et al 2014 because it does not take into account the RS effect at the longer wavelengths used.

 

[elerner]

If this hypothesis was correct and the universe is not expanding, is eternal, and is evolving as a function of time, why would not all the stars have burned out an infinite time ago?

In the Big Bang model, evolution slows down without limit going forward in time. So as you go forward in time, you would eventually get to a time without stars, without galaxies, etc. But evolution in the universe can speed up with time, as we know to be the case here on Earth. Similarly, if you extrapolate the observed accelerating evolution backwards in time, you get a slower evolution the further back you are. Therefore any stage of evolution of the universe--the formation of galaxies, the formation of stars etc. could have begun a finite time ago, but not the universe itself.

 

[Eric Bretschneider]

The assumption that galaxies should appear larger in an expanding universe of course requires that you know the current distance to the galaxy. The issue I have is that regardless of whether or not the universe is expanding, galaxy size is measured based on the distance to the galaxy when the light was emitted. We don't see galaxies at their current distance, only the distance long ago in the past.

 

[Jean Tate]

it seems that there's rather a lack of interest in my proposal (to independently try to verify the GALEX results reported in L14)

This is outside the scope of PF. Independent replication of scientific results is original research, which is not what PF is for.

Thanks. Got it.

 

[Jean Tate]

While this thread was locked, there was an exchange in a thread in International Skeptics Forum that I think is highly pertinent:

Eric;
For the sake of brevity, could you please provide maybe a link to the specific Galex dataset(s) you used?
Thanks

http://galex.stsci.edu/casjobs/

If Jean Tate provides a place to put them I can at some point--not the next few days but the next few weeks--post an excel file of our GALEX data.

My only suggestion, for now, is as before: GitHub. While I do have an account there, I would rather not host your data @elerner. Could I suggest that you set up a GitHub account (if you don't already have one)? Also, may I suggest that you convert any excel file to a CSV before posting it?

 

[Jean Tate]

From before this thread was temporarily locked:

<snip>
However, I'm even more curious about how you "fitted the radial brightness profile with a disk law excluding the central 0.1 arcsec for HST and 5 arcsec for GALEX".

For example, did you write your own code? Or use a publicly available tool or package? Something else??

I will try to ask you only one question at a time @elerner, and wait for an answer before asking another.

 

[elerner]

This is an easy one, said Humpty Dumpty. My colleagues wrote their own code. The basic algorithm is simple. Once you convert the profile to a logarithmic one, the exponential disk fit is just a straight line, so easy to fit.

 

[Jean Tate]

This is an easy one, said Humpty Dumpty. My colleagues wrote their own code. The basic algorithm is simple. Once you convert the profile to a logarithmic one, the exponential disk fit is just a straight line, so easy to fit.

Thanks!

My follow-on is more than one question, but all related, so I hope that's OK (all about the GALEX data).

Did you deconvolve the PSF? If so, how? And what did you use for the PSF?

Did you do a 1D or a 2D fit? If the former, which axis through the center did you use? If the latter, how did you de-project the disks (since very few will be seen close enough to face-on)?

 

[ruarimac]

Of course I can. It concerns different sets of data that still relate to the same size question. If you have just the disk size data, you can certainly fit it ex post facto with sufficient numbers of free variables.

These simulations have been run. They were not calibrated to your data. Comparing your results to them is not fitting anything, as I explained.

So for ellipticals you can't fit the size data, the merger data and the velocity data no matter what you do.

Then you have no reason not to look at recent simulations.

In fact this claim seems to be to be entirely untested in the paper. The only physical model you plot against elliptical data is the Mo et al. model, which is for disks, not ellipticals. You seem to have concluded that no model can fit this data, by testing no models of ellipticals whatsoever. Your cosmological claims rest on this elliptical data not being able to be fit by any expanding universe model, but you haven't tested any models of it. Furthermore people have actually shown that simulations (EAGLE) reproduce van der Wel's data. You claim van der Wel's has made mistakes but I don't think you have demonstrated that.

In the case you cited of Eagle, they claim a good fit to van der Wels. But in section 7 of my paper, I show why van der Wel's disk data disagrees with both Shibuya and Lerner et al 2014 because it does not take into account the RS effect at the longer wavelengths used.

I'm honestly don't believe this "resolution-size" effect really exists. Your only demonstration of this in the paper is to compare GALEX and SDSS galaxy sizes. You don't seem to consider the possibility that galaxy sizes can be different in different bands, asserting that because the relation is not 1-to-1 it must be an effect of the surveys. That doesn't follow. You also don't consider that catalogue sizes may not be measured consistently. Measuring sizes with barely resolved objects will always be difficult but if you actually model the process of fitting sizes any bias can be simulated. I'm aware that people have tested the ability to measure sizes of between ground based imaging and HST, the results correlation is much tighter than in your test, the bias is much smaller and has the opposite sign. If this "RS effect" were real then the all lower resolution imagery would be biased to higher radii, but that isn't what other people have found.

http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1708.00005

van der Wel on the other hand studied the wavelength dependence of their size measurements with the different HST bands, the PSF is different between different bands and so any substantial effect there would be folded in. They fit the sizes themselves so this is a much better test that your GALEX SDSS comparison because they're measured consistently. Given that you have different selection functions and are measuring in different bands it's hardly surprising there is disagreement, it doesn't imply van der Wel is wrong. Just to summarise my key point, the Almaini paper I linked demonstrated this RS effect is not some blanket effect. This disproves your criticism of van der Wel, therefore the comparison with the EAGLE simulations has already demonstrated that recent simulations can fit the size evolution. The claim that this is evidence against an expanding universe just doesn't hold any water.

 

[SelfSim]

Eric;

We are pursuing the data from the link you posted at ISF. We sampled similar data (for the M31 region) and found that it contained very high levels of backgound noise (confirmed by a Pixinsight measurement of σ = 1.358 x 10 ̄ ² for a sample of the M31 region). We used AIP4WIN software to compare resulting FWHM figures across both software packages.

In both cases the FWHMs are rejected due to the high background noise, due to the difficulty of accurately determining a radius value in order to calculate the FWHMs.
We conclude that this would have also have been the case in Lerner's etal's radius measurements.

Which leads us to our rather simple question of:

'Did you perform your radius measurements on single image data, or stacked data?'

(We also note that irrespective of how Lerner etal performed the measurements, the cutoff results are around 50% of the specified FWHM .. instead of being the lower limit of derived FWHM values).

Looking forward to your response.
Cheers

 

[PeterDonis]

In the Big Bang model, evolution slows down without limit going forward in time.

I have not seen this in any description of the standard Big Bang model. Where are you getting it from?