Rumours about potential WMAP 2nd year discoveries

Sarah Bridle
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Rumours about potential WMAP 2nd year discoveries

Post by Sarah Bridle » September 25 2004

Heard any good rumours about what the WMAP 2nd year results might have discovered?
There seems to be one about them finding a cosmic string. Is this even feasible given the noise levels/resolution etc?

Alessandro Melchiorri
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Post by Alessandro Melchiorri » September 26 2004

Yes, I heard the same rumour but it was around April 1st... :-)
I don't think you can see a Kaiser-Stebbins effect with the
angular resolution of WMAP.
There is claim for a cosmic string by a lensing candidate in
astro-ph/0406516 but is at much smaller angular scales !
Anyway, it would be really GREAT if this is true.
Here (IMHO) my bets on the 2nd year results:

- New EE spectra and bounds on BB.
- tau-> 0.1 sigma_8->0.8
- _much_ better bounds on inflationary parameters.
- "Glitches" in the TT spectrum data gone away.

What do you think ? :-)

Anze Slosar
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Post by Anze Slosar » September 27 2004

Let's not forget there were several few-sigma detections of non-gaussianities in the data so maybe some of them might turn out interesting... However, I would be very surprised with if we got from a detection of some sort to a complete understanding with just factor of 2 imporvement in noise (except if there's something funny at the same spot in polarisation map).

I would be also quite interested what will they make of galactic plane assymetries, and stuff, they have to at least prepare some sort of answer...

Hans Kristian Eriksen
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Post by Hans Kristian Eriksen » September 27 2004

Anze Slosar wrote:Let's not forget there were several few-sigma detections of non-gaussianities in the data so maybe some of them might turn out interesting... However, I would be very surprised with if we got from a detection of some sort to a complete understanding with just factor of 2 imporvement in noise (except if there's something funny at the same spot in polarisation map).

I would be also quite interested what will they make of galactic plane assymetries, and stuff, they have to at least prepare some sort of answer...
Basically all the reported non-Gaussianities are of large-scale nature (with the single exception of Chiang's phase analysis, I think), where the first-year WMAP signal-to-noise ratio is excellent. So I would be very surprised if any of these are significantly changed in the second-year data, assuming they haven't found a serious systematic effect which now has been corrected. In fact, if these effects *do* disappear without a good explanation, I would be very concerned...

Alessandro Melchiorri
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Post by Alessandro Melchiorri » September 27 2004

Uhm...these experiments are so difficult to make !
Personally, I would not consider a big deal any appeareance and/or disappearence of non gaussianities at 2 sigma level.
Low quadrupole included. (IMHO of course , :-)).

Hans Kristian Eriksen
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Post by Hans Kristian Eriksen » September 27 2004

Alessandro Melchiorri wrote:Uhm...these experiments are so difficult to make !
Personally, I would not consider a big deal any appeareance and/or disappearence of non gaussianities at 2 sigma level.
Low quadrupole included. (IMHO of course , :-)).
Well, I think there are two different issues involved here. The non-Gaussianities reported so far are, as you say, mostly marginal (two to three sigma or so), but that is mainly because of cosmic variance. The cosmic variance is not going to change in the second year WMAP data, and the noise doesn't matter much at these scales. So if these large-scale effects do change in the second-year data, there better be a good explanation for it.

Pablo Fosalba
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Post by Pablo Fosalba » September 28 2004

Alessandro Melchiorri wrote:Yes, I heard the same rumour but it was around April 1st... :-)
I don't think you can see a Kaiser-Stebbins effect with the
angular resolution of WMAP.
There is claim for a cosmic string by a lensing candidate in
astro-ph/0406516 but is at much smaller angular scales !
Anyway, it would be really GREAT if this is true.
Here (IMHO) my bets on the 2nd year results:

- New EE spectra and bounds on BB.
- tau-> 0.1 sigma_8->0.8
- _much_ better bounds on inflationary parameters.
- "Glitches" in the TT spectrum data gone away.

What do you think ? :-)
Joinning Alessandro and Hans's discussion on expectations,
I agree with them except for a couple of things:

-I think tau will stay high, tau =0.15-0.2, and sigma_8 =0.9-0.95
-I tend to agree with Hans rather than Alessandro in this:
"Glitches" will remain, at least some of them: the "dent" in l~200 (which appears
whenever an inverse noise weighting scheme is applied to the data) seems quite robust
--it was seen in Archeops too-- and I dont think there is a simple cause for
systematics on that particular scale.


-Some sytematics might be found and perhaps removed on large to intermadiate scales
(we found some trace of those in a recent paper, astro-ph/0405589).
The overall chi2 for a best-fit model could then go down wrt published WMAP1.

-I dont expect much about non-Gaussianity. Marginal detections perhaps.

also,

- Some trace of SZ effect on higher l-s ? thats possible with lower noise on highest l's
than in WMAP1.

-I really expect a lot from the polarization data: probably lots of work
is going in the direction of understanding systematics there, so I expect
a really nice paper discussing many new issues/methods/algorithms
that will be very useful for future experiments (such as Planck).

Alessandro Melchiorri
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Post by Alessandro Melchiorri » September 28 2004

Uhm, I heard that in the 2nd release of ARCHEOPS the "dent" is disappeared !
Do you anything about this ?
ciao!

Sarah Bridle
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Dent in 1st peak of Archeops data

Post by Sarah Bridle » September 28 2004

Matthieu Tristram gave a talk on Archeops last week at COSMO04 and the dent still looked like it was there on the plots to me. There was no comment about it having disappeared. I asked about the significance of the dent, and he stressed that the errors are not small enough from Archeops to call it a significant feature (from Archeops alone..).

Alessandro Melchiorri
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Post by Alessandro Melchiorri » October 05 2004

Ok, I just saw the paper by Tom Kibble today: astro-ph/0410073.
He cites another possible candidate for cosmic string: astro-ph/0406434.

Alessandro Melchiorri
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Post by Alessandro Melchiorri » October 19 2004

Just heard a new rumour...WMAP2 detected B modes... :-)

Anze Slosar
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Post by Anze Slosar » October 19 2004

Alessandro Melchiorri wrote:Just heard a new rumour...WMAP2 detected B modes... :-)
*%^&* ! How serious is this rumour? They (b modes) would have to be seriously strong for this to be true. But, if this is the case, I would predict a quiet streem of papers on inflationary models producing large B, which I haven't seen...

anze

Hans Kristian Eriksen
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Post by Hans Kristian Eriksen » October 20 2004

Alessandro Melchiorri wrote:Just heard a new rumour...WMAP2 detected B modes... :-)
Detected or observed? :-)

They may perhaps see quite a lot of B-modes in their maps, but that would most likely be due to systematics and foregrounds. If you look at their beams on Lambda,

http://lambda.gsfc.nasa.gov/product/map ... _sideA.png

and

http://lambda.gsfc.nasa.gov/product/map ... _sideB.png ,

you will see that they are quite asymmetric and different between the A and B sides. Neither effect is very comforting when trying to measure B-mode (or even E-mode) polarization.

Pablo Fosalba
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WMAP2

Post by Pablo Fosalba » October 20 2004

Hans Kristian Eriksen wrote:
Alessandro Melchiorri wrote:Just heard a new rumour...WMAP2 detected B modes... :-)
Detected or observed? :-)

They may perhaps see quite a lot of B-modes in their maps, but that would most likely be due to systematics and foregrounds. If you look at their beams on Lambda,

http://lambda.gsfc.nasa.gov/product/map ... _sideA.png

and

http://lambda.gsfc.nasa.gov/product/map ... _sideB.png ,

you will see that they are quite asymmetric and different between the A and B sides. Neither effect is very comforting when trying to measure B-mode (or even E-mode) polarization.

I wdn't be surprised if they had been spending quite a lot of time trying to figure out
something like that, whether measured B modes are systematics or truely cosmological in origin. Perhaps that explains part of the delay in the data release ?

Alessandro Melchiorri
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Rumours about potential WMAP 2nd year discoveries

Post by Alessandro Melchiorri » February 16 2005

Hi all,
I heard another rumor (BTW always from someone not involved in the WMAP team).
The rumour is that the optical depth is now much more consistent with the standard scenario and \tau is around 0.1.
Comments ?

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