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trinitree88
2017-Jun-16, 03:06 PM
"Are we missing a signature of dust?", the Author Vaclav Vavrycuk, asks. It seems that a galactic , and an intergalactic signature should be looking at us but is not in data that should,by his regards, show it. SEE:https://arxiv.org/abs/1706.04771 pete

Jerry
2017-Jun-25, 01:06 PM
"In such theory, the CMB should not be distorted because the CMB would concurrently be absorbed and reradiated by dust. In any case, it is
clear that the missing dust imprint on the CMB is an intriguing puzzle which should be further studied and confronted with current measurements and models of the Universe."

You could replace the word 'would' with 'is'. Radiation transfer mechanics are no different in space that they are in the ocean: A wave is a wave.

kzb
2017-Jun-26, 12:19 PM
"In such theory, the CMB should not be distorted because the CMB would concurrently be absorbed and reradiated by dust. In any case, it is
clear that the missing dust imprint on the CMB is an intriguing puzzle which should be further studied and confronted with current measurements and models of the Universe."

You could replace the word 'would' with 'is'. Radiation transfer mechanics are no different in space that they are in the ocean: A wave is a wave.

I think the argument is: the CMB is almost perfect black-body radiation -but if there is dust in the light path, the CMB spectrum should show dips and spikes in accordance with the mineral composition of the dust. But it doesn't (see Fig. 2 in the paper).

I guess the energy absorbed by dust must equal the energy re-radiated, at equilibrium, but I think the point is, it would not retain the same spectrum shape. Obviously I am no expert but that was my take on it.

ngc3314
2017-Jun-26, 01:53 PM
You wouldn't expect to see individual spectral features- they would be smeared out by the large redshift range where dust reprocessing occurs. This is why the paper's main results show only a very smooth distortion of the blackbody form (I really really wish they were plotted as relative distortion rather than in energy units...)

I'm not sure right off how good our measurements of long-wavelength dust radiation properties are - it's common to express the modification to blackbody emission (when wavelengths are many times longer than the grain dimensions) as a power-law index in wavelength, but AFAIK that's been something empirically estimated by fits to energy distributions assuming a floor on grain temperature rather than calculated from more basic physics.

kzb
2017-Jun-26, 04:12 PM
You wouldn't expect to see individual spectral features- they would be smeared out by the large redshift range where dust reprocessing occurs. This is why the paper's main results show only a very smooth distortion of the blackbody form (I really really wish they were plotted as relative distortion rather than in energy units...)

I'm not sure right off how good our measurements of long-wavelength dust radiation properties are - it's common to express the modification to blackbody emission (when wavelengths are many times longer than the grain dimensions) as a power-law index in wavelength, but AFAIK that's been something empirically estimated by fits to energy distributions assuming a floor on grain temperature rather than calculated from more basic physics.

So, basically you are saying there are two possibilities:

(1) The observations are not sensitive enough to measure the predicted effect with any confidence

and/or

(2) Not enough is known to model what is the predicted effect of dust in this situation ?

Jerry
2017-Jul-14, 07:06 PM
So, basically you are saying there are two possibilities:

(1) The observations are not sensitive enough to measure the predicted effect with any confidence

and/or

(2) Not enough is known to model what is the predicted effect of dust in this situation ?

A little bit of both. When the first year WMAP data was reduced, they found 'unexpected' variations that were attributed to small changes the differential receiver's temperature, and an equation was developed that filtered-out unlikely zags in the strip-wise maps.

But when the algorithm was applied to WMAP third year data, there was limited consistency between the two maps. Eventually the data was smoothed using pixel-by-pixel corrections. (There were assumptions made about dust levels, but if my memory is correct the data that we have today on dust microwave properties was not available at that time.)

The net result is a sky-wide map that is congruent with expectations, but there is no way that this type of analytical approach could be used to refute established theories about background radiation.

Shaula
2017-Jul-14, 07:22 PM
A little bit of both. When the first year WMAP data was reduced, they found 'unexpected' variations that were attributed to small changes the differential receiver's temperature, and an equation was developed that filtered-out unlikely zags in the strip-wise maps.

But when the algorithm was applied to WMAP third year data, there was limited consistency between the two maps. Eventually the data was smoothed using pixel-by-pixel corrections. (There were assumptions made about dust levels, but if my memory is correct the data that we have today on dust microwave properties was not available at that time.)

The net result is a sky-wide map that is congruent with expectations, but there is no way that this type of analytical approach could be used to refute established theories about background radiation.
Can you provide detailed references for these claims? Because the literature I have read on this paints quite a different picture to the one you do.

Jerry
2017-Jul-14, 11:44 PM
Can you provide detailed references for these claims? Because the literature I have read on this paints quite a different picture to the one you do.

[answer removed because it referenced a ATM source.]

See https://arxiv.org/pdf/1001.4744.pdf for a good overview of the seven year data reduction techniques.

Shaula
2017-Jul-15, 07:49 AM
[answer removed because it referenced a ATM source.]

See https://arxiv.org/pdf/1001.4744.pdf for a good overview of the seven year data reduction techniques.
Yes, I am familiar with the data reduction techniques. And they do not support your claims.

I am guessing (since you didn't provide any detail) that your claims about pixel to pixel corrections are based on the Diffuse Galactic Foreground corrections? Just because you mention dust. If you read what they do they don't adjust pixel values as you suggest. What they do is remove isolated anomalous pixels from the dust correction layer and infill using surrounding values. Then apply this layer to the data. They also derive their chi-squared cut threshold from the polar data and apply it to the in-plane data.

Or were you talking about the Transmission Imbalances? Or something else?

You clearly believe there is an issue - can you point it out in detail? These kinds of vague accusations of poor analytical method don't really help anyone. If you can point out precisely why the methods used are flawed then you should do so. Otherwise you should stop making claims you cannot support.