Error in CMB Interpretation? Implications?

[Saul]

As noted in the thread "Dark Matter, On the Ropes?" there is disagreement with the observed velocity profile of spiral galaxies, the size of spiral galaxies' bulge, and the spiral galaxies' halo when compared to what theory predicts and what simulations with dark matter indicate.

http://www.physics.utah.edu/~vdbosch/disks2.pdf

There is a list of the issues from a seminar presentation.

=⇒ Angular Momentum Catastrophe
⋆ haloes have too much low angular momentum material
=⇒ Morphology Problem! Too much bulge, too little disk
⋆ Standard model can not fit TF zero point
=⇒ Haloes are too centrally concentrated

Those discrepancies and the negative results for laboratory dark matter detection may indicate that dark matter does not exist.

One of the observations which was believed to indicate that both dark matter and dark energy exists was the large scale variance of the cosmic microwave background radiation (CMB).

This recent paper challenges that finding. If the authors' analysis is correct it appears to indicate that both dark matter and dark energy do not exist.

Perhaps the new CMB data from the Planck satellite will help to resolve the issue.

http://www.sciencedaily.com/releases/2010/06/100613212708.htm

Sawangwit and Shanks used astronomical objects that appear as unresolved points in radio telescopes to test the way the WMAP telescope smoothes out its maps. They find that the smoothing is much larger than previously believed, suggesting that its measurement of the size of the CMBR ripples is not as accurate as was thought. If true this could mean that the ripples are significantly smaller, which could imply that dark matter and dark energy are not present after all.

If the Universe really has no 'dark side', it will come as a relief to some theoretical physicists. Having a model dependent on as yet undetected exotic particles that make up dark matter and the completely mysterious dark energy leaves many scientists feeling uncomfortable. It also throws up problems for the birth of stars in galaxies, with as much 'feedback' energy needed to prevent their creation as gravity provides to help them form.

http://arxiv.org/PS_cache/arxiv/pdf/0912/0912.0524v2.pdf

Beam profile sensitivity of the WMAP CMB power spectrum

http://arxiv.org/PS_cache/arxiv/pdf/1006/1006.1270v1.pdf

ΛCDM and the WMAP power spectrum beam profile sensitivity

http://arxiv.org/abs/0908.1409v1

Galactic Disk Formation and the Angular Momentum Problem
Galaxy formation to some extent is an initial condition problem. Whether a galactic disks can form at all depends on the amount of angular momentum present in the infalling gas. The disk structure is determined by the gravitational potential of the baryonic and dark component of the galaxy and the specific angular momentum distribution of the fraction of infalling gas that can cool and dissipate its potential and kinetic energy while settling into centrifugal equilibrium in the equatorial plane. Once a massive disk has formed and on timescales longer than the infall timescale secular disk evolution will become important, resulting in angular momentum redistribution of gas and stars in the disk by viscous effects and gravitational torques, coupled with star formation and selective gas loss in galactic winds (Kormendy & Kennicutt 2004).

The origin of angular momentum is generally believed to be cosmological. Before and during the early phase of protogalactic collapse, gas and dark matter are well mixed and therefore acquire a similar specific angular momentum distribution (Peebles 1969; Fall & Efstathiou 1980; White 1984). If angular momentum would be conserved during gas infall, the resulting disk size should be directly related to the specific angular momentum ′ of the surrounding dark halo where (Bullock et al. 2001)

 

[Saul]

This is an expanded press release from the University of Durham that explains the findings and the associated theoretical issues.

http://star-www.dur.ac.uk/~dph3us/cmb_press_release.doc

http://star-www.dur.ac.uk/~dph3us/cosmology.html

 

[nicksauce]

It seems to be an incredible stretch to go from

"It will be interesting to see if a revised estimate of the WMAP beam profile then allows a simpler cosmological model to be fitted than LCDM."

to

"If the authors' analysis is correct it appears to indicate that both dark matter and dark energy do not exist."

 

[Saul]

It seems to be an incredible stretch to go from

"It will be interesting to see if a revised estimate of the WMAP beam profile then allows a simpler cosmological model to be fitted than LCDM."

to

"If the authors' analysis is correct it appears to indicate that both dark matter and dark energy do not exist."

Attached is another paper by the same authors and a discussion by a specialist in the field that explains why beam width changes the resultant and if the measurement is correct the conclusion as to whether the CMB analysis does or does not support the existence of dark matter and dark energy.

The raw CMB signal measured by the Wilkinson Microwave Anisotropy Probe WMAP is adjusted for assumed foreground signals and is adjusted for beam width. (See figure 1 in this paper which compares the raw CMB signal to what we see in typical books and on the web.

That mathematical change is very sensitive to the beam width which was determined by measurements with Jupiter. When the beam width is measured with distance astronomical objects a significantly wider beam width is found.

Using the wider beam width the resulting mathematical resultant no longer supports dark matter and dark energy. That finding is supported by other recent papers which challenge the validity of dark matter and dark energy by different analysis.


http://arxiv.org/abs/1006.1270v1

ΛCDM and the WMAP power spectrum beam profile sensitivity

Figure 1: The red line shows the raw WMAP W band power spectrum estimated from the cross-correlation of the WMAP5 W1 and W2 maps. The blue diamonds + line shows the final WMAP5 spectrum after ‘de-beaming’ using the Jupiter beam( +‘cut-sky’ correction). The large effect of de-beaming even at the first acoustic peak (approx 1deg) is caused by beam sidelobes, even though the beam’s Gaussian core has a width of only 12.06 FWH

We first discuss the sensitivity of the WMAP CMB power spectrum to systematic errors by calculating the raw CMB power spectrum from WMAP data. We find that the power spectrum is surprisingly sensitive to the WMAP radiometer beam profile even at the position of the first acoustic peak on approx. 1 degree scales.

We then test the form of the beam-profile used by the WMAP team which is based on observations of Jupiter. We stacked radio source beam profiles as observed in each WMAP band and found that they showed a wider profile in Q, V, W than the Jupiter profile. We have now checked that this is not due to any Eddington or other bias in our sample by showing that the same results are obtained when radio sources are selected at 1.4GHz and that our methods retrieve the Jupiter beam when it is employed in simulations. Finally, we show that the uncertainty in the WMAP beam profile allows the position as well as the amplitude of the first peak to be changed and how this could allow simpler cosmologies than standard ΛCDM to fit the CMB data.

http://telescoper.wordpress.com/2010/06/14/cosmology-on-its-beam-ends/

At each frequency the sky is blurred out by the “beam” of the WMAP optical system; the blurring is worse at low frequencies than at high frequencies. In order to do the foreground subtraction, the WMAP team therefore smooth all the frequency maps to have the same resolution, i.e. so the net effect of optical resolution and artificial smoothing produces the same overall blurring (actually 1 degree). This requires accurate knowledge of the precise form of the beam response of the experiment to do it accurately. A rough example (for illustration only) is given in the caption above.

Now, here are the power spectra of the maps in each frequency channel….

I haven’t got space-time enough to go into how the foreground subtraction is carried out, but once it is done it is necessary to “unblur” the maps in order to see the structure at small angular scales, i.e. at large spherical harmonic numbers l. The initial process of convolving the sky pattern with a filter corresponds to multiplying the power-spectrum with a “window function” that decreases sharply at high l, so to deconvolve the spectrum one essentially has to divide by this window function to reinstate the power removed at high harmonics.

This is where it all gets very tricky. The smoothing applied is very close to the scale of the acoustic peaks so you have to do it very carefully to avoid introducing artificial structure in Cl or obliterating structure that you want to see. Moreover, a small error in the beam gets blown up in the deconvolution so one can go badly wrong in recovering the final spectrum. In other words, you need to know the beam very well to have any chance of getting close to the right answer!

The next picture gives a rough model for how much the “recovered” spectrum depends on the error produced by making even a small error in the beam profile which, for illustration only, is assumed to be Gaussian. It also shows how sensitive the shape of the deconvolved spectrum is to small errors in the beam.

 

[Chronos]

A published paper does not lend credibility to a fringe perspective. Where is the blow by blow dismantling of the body of evidence supporting dark matter? My grandfather was an accomplished magician. I learned more watching his off hand than the one waving the wand.

 

[bapowell]

It's irresponsible to make claims about which models fit and don't fit your data until you...ummm...do an analysis on which models fit and don't fit your data. They need to do a thorough Bayesian analysis, preferably with a model selection component, in order to make such claims.

 

[Saul]

It's irresponsible to make claims about which models fit and don't fit your data until you...ummm...do an analysis on which models fit and don't fit your data. They need to do a thorough Bayesian analysis, preferably with a model selection component, in order to make such claims.

I am not sure what logical point you have.

Increasingly sophisticated experiments have not been able to detect dark matter. Yes?

The observed spiral galaxy morphology and rotational curve is not in agreement with simulations that use dark matter. Yes?

The last argument, the last leg of the three legged stool, for dark matter has the CMB profile matches what was predicted.

What we find is an independent measurement of a key parameter required for the data calculation invalidates the CMB resultant curve.

The irrational statement that it is better to believe in something that does not exist than to have no theory at all, is comical. Believe in what every you want to believe in. Dark matter appears to be more a road block or a dead end, based on the analysis and observations.

It is very normal for results to exactly match predictions when everyone believes the theory is correct. When new observations fundamentally challenge the theory, people look for and find errors in the original analysis. That has happened before and is what makes us human.

If dark matter does not exist, it is back to the drawing board. The rotational anomaly for spiral galaxies still requires an explanation. As noted in the press release there has been the discovery of very large anomalous high temperature gas in the vicinity of clusters which is explaining the anomalous motion in clusters. There was a paper that showed that detailed analysis of Elliptical galaxy star motion did not support the existence of dark matter in the vicinity of elliptical galaxies.

And I might add I do not support the theories that appeal to magic (close your eyes, tap your heels together three times and the universe will change as it is a hologram) such as the anthropological principal, or strings, or the 10th dimension as an explanation. Come back when there is a theory with predictions. There is obviously no fundamental base in physics. A quadrillion monkeys will not type out the correct theory. Guessing is not science.

http://en.wikipedia.org/wiki/Anthropic_principle

 

[bapowell]

You miss my point Saul. The point is not to debate the existence of dark matter, or the merits of including a dark matter component in simulations or parameter estimation analyses. The point is that the authors make a claim about the status of dark matter based on the increase in error bars of the CMB temperature and polarization maps without having actually done the analysis. Surely there's nothing illogical about requesting that someone actually do an analysis before making claims as to the outcome of that analysis.

I don't see what the rest of your rant has to do with this thread though.

 

[Saul]

You miss my point Saul. The point is not to debate the existence of dark matter, or the merits of including a dark matter component in simulations or parameter estimation analyses. The point is that the authors make a claim about the status of dark matter based on the increase in error bars of the CMB temperature and polarization maps without having actually done the analysis. Surely there's nothing illogical about requesting that someone actually do an analysis before making claims as to the outcome of that analysis.

I don't see what the rest of your rant has to do with this thread though.

I do not understand your comment. Shanks does calculations in his paper.

Read the first page of his paper. Shanks has a problem with handwaving magic explanations. What you call rants appears to be a paraphrase of what Shanks states in the first page in his paper. (Let's leave his comments in the first page of his paper, as each bullet point deserves a separate thread.)

His is asserting that a change in the beam profile invalidates the CMB calculations.

http://arxiv.org/abs/1006.1270v1

Lambda-CDM and the WMAP power spectrum beam profile sensitivity
We first discuss the sensitivity of the WMAP CMB power spectrum to systematic errors by calculating the raw CMB power spectrum from WMAP data. We find that the power spectrum is surprisingly sensitive to the WMAP radiometer beam profile even at the position of the first acoustic peak on ~1 degree scales. Although the WMAP beam profile core is only 12.6arcmin FWHM at W, there is a long power-law tail to the beam due to side-lobes and this causes significant effects even at the first peak position. We then test the form of the beam-profile used by the WMAP team which is based on observations of Jupiter. We stacked radio source beam profiles as observed in each WMAP band and found that they showed a wider profile in Q, V, W than the Jupiter profile. We have now checked that this is not due to any Eddington or other bias in our sample by showing that the same results are obtained when radio sources are selected at 1.4GHz and that our methods retrieve the Jupiter beam when it is employed in simulations. Finally, we show that the uncertainty in the WMAP beam profile allows the position as well as the amplitude of the first peak to be changed and how this could allow simpler cosmologies than standard Lambda-CDM to fit the CMB data.

 

[Chronos]

You are still watching the wand, Saul.

 

[bapowell]

In which paper does he do the kinds of calculations I'm talking about? I'm not saying he does *no* calculations whatsoever. I'm saying he has not conducted a Bayesian parameter estimation/model selection analysis of the type necessary to make the claims he's making. I am not doubting the possibility that something is wrong with the beam smoothing used by WMAP -- I'm simply pointing out that I think his paper could be much improved by including such an analysis. Then he could concretely say something like: "I've removed dark matter from my CMB analysis, and I still obtain as good a likelihood as when I include it. This suggests that dark matter is perhaps an unneeded parameter in describing the physics of the acoustic peaks of the CMB". Or something like that.