[astro-ph/0508047] On the large-angle anomalies of the microwave sky

Authors:  C. J. Copi (1), D. Huterer (2), D. J. Schwarz (3), G. D. Starkman (1) ((1) Case Western Reserve University, (2) University of Chicago, (3) Universitat Bielefeld)
Abstract:  [Abridged] We apply the multipole vector framework to full-sky maps derived from the first year WMAP data. We significantly extend our earlier work showing that the two lowest cosmologically interesting multipoles, l=2 and 3, are not statistically isotropic. These results are compared to the findings obtained using related methods. In particular, the planes of the quadrupole and the octopole are unexpectedly aligned. Moreover, the combined quadrupole plus octopole is surprisingly aligned with the geometry and direction of motion of the solar system: the plane they define is perpendicular to the ecliptic plane and to the plane defined by the dipole direction, and the ecliptic plane carefully separates stronger from weaker extrema, running within a couple of degrees of the null-contour between a maximum and a minimum over more than 120deg of the sky. Even given the alignment of the quadrupole and octopole with each other, we find that their alignment with the ecliptic is unlikely at >98% C.L., and argue that it is in fact unlikely at >99.9% C.L. We explore the role of foregrounds showing that the known Galactic foregrounds are unlikely to lead to these correlations. Multipole vectors, like individual a_lm, are very sensitive to sky cuts, and we demonstrate that analyses using cut skies induce relatively large errors, thus weakening the observed correlations but preserving their consistency with the full-sky results. Finally we apply our tests to COBE cut-sky maps and briefly extend the analysis to higher multipoles. If the correlations we observe are indeed a signal of non-cosmic origin, then the lack of low-l power will very likely be exacerbated, with important consequences for our understanding of cosmology on large scales.
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Garth Antony Barber
Posts: 59
Joined: July 19 2005
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[astro-ph/0508047] On the large-angle anomalies of the micro

Post by Garth Antony Barber » August 06 2005

Is the CMB contaminated with a local signal that affects the low l mode data?
If so what would this do to the standard concordant infinite and almost flat model?

Garth Antony Barber
Posts: 59
Joined: July 19 2005
Affiliation: Published independent

[astro-ph/0508047] On the large-angle anomalies of the micro

Post by Garth Antony Barber » September 05 2005

No comments? A further paper today: astro-ph/0509039 "Local Pancake Defeats Axis of Evil" makes the following points:
1. The low l-mode deficiency being a statistical fluke is unlikely
The original low quadrupole anomaly has long been dismissed as either the result of some residual systematic error or as a statistical fluke. However, the higher quality of data now available from WMAP strongly challenge the residual systematic explanation (Tegmark et al. 2003), and while a statistical fluke cannot be ruled out, the odds against are uncomfortably long. In one recent study, Copi et al. (2005) have used the multi-pole vector formalism to show that a purely accidental alignment is unlikely in excess of 99.9%. They have also shown that most of the ℓ = 2 and ℓ = 3 multi-pole vectors of known Galactic foregrounds are located far away from those observed in WMAP data, strongly suggesting that residual contamination by foregrounds which are currently included in the analysis is not a viable explanation. It is precisely this combination of a complete lack of any known systematic error, and long odds against random alignment that has earned the low-ℓ alignment anomaly the nickname “Axis of Evil”
2.It explains the "Axis of Evil" by gravitational lensing of the CMB dipole, which may be modelled by [tex]M_{solar}^{17}[/tex] (~twice Great attractor) at a distance of 30 Mpc, or even by our own Galaxy if the DM halo is more massive and planar than expected.:
Weak lensing of the CMB has long been a topic of interest to cosmologists (e.g. Seljak 1996; Zaldarriaga & Seljak 1998; Hu 2000; Challinor & Lewis 2005). The effect is both simple and inescapable; all light which reaches us from the surface of last scattering (or any other source, for that matter) is deflected from its original path by the weak gravitational lensing interaction with the matter distribution along the line of sight (see Bartelmann & Schneider 2001, for a comprehensive review), and no exceptions are made for photons from the CMB dipole. Although the dipole owes its existence to the motion of the observer with respect to the background, this makes no difference from the perspective of someone in the same frame of reference as the observer; one side of the universe is simply hotter than the other, and this anisotropy will be lensed. We note that since the dipole term measured by WMAP (given in Bennett et al. 2003b, as 3.346 cosθ mK in the direction (ℓ, b) = (263.◦85, 48.◦25) in Galactic coordinates) is more than two orders of magnitude larger than the quadrupole term (and is by far the largest anisotropy in the CMB), even sub percent level scatter will strongly effect the low ℓ moments. Also, because the dipole is coherent over the whole sky, it will couple best to lensing effects that are also coherent over much of the sky, so that local structures will be the dominant lenses.
3.:
This leads us directly to our next point; while it appears that we may have gone a long way toward eliminating the axis alignment problem, the effect of dipole lensing is to take power away from the dipole and add it to the higher moments, so that the low quadrupole anomaly is stronger than ever.
An over-estimation of the low-l power modes would cause problems in the WMAP analysis of other cosmological parameters, so again perhaps talk the "age of precision cosmology" is a little premature!
Garth

Boud Roukema
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Re: [astro-ph/0508047] On the large-angle anomalies of the m

Post by Boud Roukema » September 06 2005

Garth Antony Barber wrote:Is the CMB contaminated with a local signal that affects the low l mode data?
If so what would this do to the standard concordant infinite and almost flat model?
I don't think any serious observer or theorist really claims that the concordance model is infinite: the concordance model is, de facto, only some extremely tiny part of the whole Universe; this tiny part contains the observable sphere and a bit outside of it. The concordance model makes no serious claims about global cosmological parameters (except by politically correct invited speakers who incorrectly use the adjective global ;).
so again perhaps talk the "age of precision cosmology" is a little premature!
I disagree. If it is confirmed that the Universe has a Poincare dodecahedral space (PDS) global geometry - see astro-ph/0310253 + astro-ph/0402608 - then Ωm ≈ 0.3, ΩΛ ≈ 0.7, H0 ≈ 70 km/s/Mpc will still remain an extremely precise estimate of the local cosmological parameters. Dropping from factors of 2−3 uncertainty to uncertainties of 10% is definitely becoming precise. Of course, people in favour of simplicity might prefer precise cosmology instead of precision cosmology. After all precise is a perfectly good adjective. (If we really want to get into post-modernist obscurationism, why not precisionisational cosmology? Doesn't that sound high-tech and impressive?)

Anyway, you might want to read some background papers - apart from those above, you might want to start from my rather compact review paper with the basics presented rather simply: astro-ph/0010185 and then go back into the older reviews if you want more depth.

The most recent workshop/conference on global cosmological parameter estimation was held at the Observatoire de Paris-Meudon in March 2005:

http://cosmo.torun.pl/cgi-bin/twiki/vie ... n2005March

Not many people have linked to their papers, but you have the names of many of the most active people in the field and looking through arXiv you should be able to find most of their recent work.

The work from my own group astro-ph/0402608 has GPL software associated so you should be able to check our analysis in an afternoon using the original data and maybe think of the next step...

In any case, the Copi et al. work definitely motivates continued work on cosmic topology... :)

Garth Antony Barber
Posts: 59
Joined: July 19 2005
Affiliation: Published independent

[astro-ph/0508047] On the large-angle anomalies of the micro

Post by Garth Antony Barber » September 06 2005

Thank you Boud, I was aware of the dodecahedral model and other topologies. How does the non-detection of 'circles-in-the-sky' affect the vaildity of such models, or is it simply that the scale is larger than at present detectable?

Would not a conformally flat model also be consistent with the WMAP peak distribution?

Garth

Boud Roukema
Posts: 84
Joined: February 24 2005
Affiliation: Torun Centre for Astronomy, University of Nicolaus Copernicus
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Re: [astro-ph/0508047] On the large-angle anomalies of the m

Post by Boud Roukema » September 07 2005

Garth Antony Barber wrote:Thank you Boud, I was aware of the dodecahedral model and other topologies. How does the non-detection of 'circles-in-the-sky' affect the vaildity of such models, or is it simply that the scale is larger than at present detectable?
Please read astro-ph/0402608 again, since it answers your question: the group I think you're referring to only looked for circles of radius larger than 25 degrees; we considered smaller circles.

But see also: astro-ph/0412569, astro-ph/0504656, astro-ph/0503014.

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