WMAP data problem?

[Wangler]

These guys claim to have found a systematic error in WMAP data analysis performed to date.

Basically, they claim that there is a bias introduced as the number of observations of a given region increases: the more observations, the higher the resulting indicated temperature. The number of observations made on a give region is based upon orbital constraints and whatnot, meaning that that bias shows as a function of RA and DEC.

At least, that's what I gathered from their paper, to be published in MNRAS.

If true, this systematic error may have implications on any inferences made from the WMAP data.

Is it plausible for these folks to have found some error missed by a whole bunch of others? I mean, the WMAP papers are co-authored by whole platoons of people.

 

[macdoc]

That's what review is about and consider the Hubble lens error and the Mariana rocket that blew up using the wrong software. ( from the previous class of rocket )

One of the Mars landers had a similar issue I think......wrong parameters ( metric versus imperial I think in that case )

WMAP is such a fundamental tho and working in such a small scale of temperature gradients one would think scrutiny would be very high....

Perhaps when too many people are engaged the scrutiny goes down instead of up as more think theotherguydidit

 

[Wangler]

These guys just won't stop..they have further analysis detailing problems with WMAP5 maps and conclusions:

Two important results are hence obtained: the CMB quadrupole drops to nearly zero, and the power in multiple moment range between 200 and 675 decreases on average by about 13%, causing the best-fit cosmological parameters to change considerably, e.g., the total matter density increases from 0.26 up to 0.32 and the dark energy density decreases from 0.74 down to 0.68. These new parameters match with improved accuracy those of other independent experiments. Our results indicate that there is still room for significant revision in the cosmological model parameters.

It seems as if we are getting closer to concrete numbers slowly but surely.

I would welcome any comments regarding the WMAP analysis of Liu, et. al. if anyone cares to join in.

 

[casebro]

I had to Wiki WMAP. Now I know ALL about it, and came to this conclusion: The cosmic microwaves are the cause of Global Warming! Forget the ice packs, tin foil hats for everybody!

 

[Wangler]

I had to Wiki WMAP. Now I know ALL about it, and came to this conclusion: The cosmic microwaves are the cause of Global Warming! Forget the ice packs, tin foil hats for everybody!

well, for the accuracy that is required by some anti-AGW folks, the exclusion of the energy contribution of the CMB is a fatal flaw in current climate modeling.....

 

[Zeuzzz]

 

[Reality Check]

It is not really a WMAP data problem. It is more a WMAP data solution
The authors point out a similarity between the known anomalous features of WMAP (e.g. the orientation of large scale patterns in respect to the ecliptic frame and the north-south asymmetry of temperature fluctuation power) and the observation number fluctuation distribution.
Their conclusion is that that flustuations in the number of observation need to be accounted for in the processing of WMAP data.

Planck will provide more and better data than WMAP in the next few years. I would expect that ore observaiton will even out the observation number fluctuation and mlessen this effect.

 

[Wangler]

Does the fact that the quadrupole appears to vanish and some of the mass fractions change with the analysis by Liu et. al. have any serious implications for our current cosmological framework, or is it just fine tuning?

 

[edd]

Does the fact that the quadrupole appears to vanish and some of the mass fractions change with the analysis by Liu et. al. have any serious implications for our current cosmological framework, or is it just fine tuning?

It sounds like just fine tuning. In fact, I've heard it said that the WMAP scan strategy was a 'masterpiece' in terms of making it so that any errors like this that might have crept in would have a very hard job affecting the cosmological parameter results. edit to add: actually there's a bit more tension going on there than I'm entirely comfortable with - I'm surprised they didn't combine their data with BAOs and SN to compare more directly to the WMAP+BAO+SN results, and show the contours for how those add up more clearly. It would give us a better idea of the significance of this on the parameters.

I'm still not personally convinced there's an issue here with the standard WMAP approach. I'd probably like to see some other kind of decomposition of the data to a set of orthogonal functions that had parts that more closely matched the smaller scale structure of the scan pattern so we could see if there was an anomalous signal in those components more easily.

And the WMAP team certainly did allow for the number of observations in their analysis, but I can't say they did it correctly (just as I can't say they didn't). I'd really want a CMB data expert to express their opinion on this.

[oh and I must say their persistent mispelling of BOOMERanG really bugs me!]

 

[Wangler]

[oh and I must say their persistent mispelling of BOOMERanG really bugs me!]

Their English usage made some parts of the paper difficult to read.

But, they certainly wrote in English better than I can write in their language, so who am I to complain?