* Astronomy

Blobrana · L

RE: CBR

Blobrana · L

Title: Cosmological Parameters from a re-analysis of the WMAP-7 low resolution maps
Authors: F. Finelli, A. De Rosa, A. Gruppuso, D. Paoletti

Cosmological parameters from WMAP 7 year data are re-analysed by substituting a pixel-based likelihood estimator to the one delivered publicly by the WMAP team. Our pixel based estimator handles exactly intensity and polarisation in a joint manner, allowing to use low-resolution maps and noise covariance matrices in T,Q,U at the same resolution, which in this work is N_{side}=16. We describe the features and the performances of the code implementing our pixel-based likelihood estimator. We perform a battery of tests on the application of our pixel based likelihood routine to WMAP publicly available low resolution foreground cleaned products, in combination with the WMAP high-\ell likelihood, reporting the differences on cosmological parameters evaluated by the full WMAP likelihood public package. The credible central value for the cosmological parameters change below the 1 \sigma level with respect to the evaluation by the full WMAP 7 year likelihood code, with the largest difference in a shift to smaller values of the scalar spectral index n_S.

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Title: CMB Multipole Alignment in the R_h=ct Universe
Authors: Fulvio Melia

An analysis of the full cosmic microwave background (CMB) sky by the Wilkinson Microwave Anisotropy Probe (WMAP) has revealed that the two lowest cosmologically interesting multipoles, the quadrupole (l=2) and the octopole (l=3) moments of the temperature variations, are unexpectedly aligned with each other. In this paper, we demonstrate that, whereas this alignment constitutes a statistically significant anomaly in the standard model, it is statistically insignificant within the context of the R_h=ct Universe. The key physical ingredient responsible for this difference is the existence in the latter of a maximum fluctuation size at the time of recombination, which is absent in LCDM because of inflation.

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Title: Non-standard morphological relic patterns in the cosmic microwave background
Authors: Joe Zuntz, James P. Zibin, Caroline Zunckel, Jonathan Zwart

Statistically anomalous signals in the microwave background have been extensively studied in general in multipole space, and in real space mainly for circular and other simple patterns. In this paper we search for a range of non-trivial patterns in the temperature data from WMAP 7-year observations. We find a very significant detection of a number of such features and discuss their consequences for the essential character of the cosmos.

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Ed ~ It is, of course, the 1st April.

Blobrana · L

Antarctica Experiment Discovers Puzzling Space Ray Pattern

A puzzling pattern in the cosmic rays bombarding Earth from space has been discovered by the IceCube Neutrino Observatory buried deep under the ice of Antarctica.
Cosmic rays are highly energetic particles streaming in from space that are thought to originate in the distant remnants of dead stars.
But it turns out these particles are not arriving uniformly from all directions. The new study detected an overabundance of cosmic rays coming from one part of the sky, and a lack of cosmic rays coming from another.
One idea to explain the asymmetry is that a star may have recently died in a supernova explosion relatively nearby, and its remnant may be pouring out loads of cosmic rays that would dominate the signals we receive.
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Durham astronomers doubts about the "Dark Side"

New research by astronomers at Durham University suggests conventional wisdom about the content of the Universe may be wrong.
Graduate student Utane Sawangwit and Professor Tom Shanks, in Durham's Department of Physics, looked at observations from the Wilkinson Microwave Anisotropy Probe (WMAP) satellite to study the remnant heat from the Big Bang.
The two scientists found evidence that the errors in its data may be much larger than previously thought, which in turn makes the standard model of the Universe open to question.
They published their results in a letter to the journal Monthly Notices of the Royal Astronomical Society.
Launched in 2001, WMAP measures differences in Cosmic Microwave Background (CMB) radiation, the residual heat of the Big Bang that fills the Universe and appears over the whole of the sky.
The angular size of the ripples in the CMB is thought to be connected to the composition of the Universe. The observations of WMAP showed that the ripples were about twice the size of the full Moon, or around a degree across.
With these results, scientists concluded that the cosmos was made up of four per cent 'normal' matter, 22 per cent 'dark' or invisible matter and 74 per cent 'dark energy'. Debate about the exact nature of the 'dark side' of the Universe - the dark matter and dark energy - continues to this day.
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Title: CMB observations in LTB universes: Part I: Matching peak positions in the CMB spectrum
Authors: Chul-Moon Yoo, Ken-ichi Nakao, Misao Sasaki
(Version v3)

Acoustic peaks in the spectrum of the cosmic microwave background in spherically symmetric inhomogeneous cosmological models are studied. At the photon-baryon decoupling epoch, the universe may be assumed to be dominated by non-relativistic matter, and thus we may treat radiation as a test field in the universe filled with dust which is described by the Lemaitre-Tolman-Bondi (LTB) solution. First, we give an LTB model whose distance-redshift relation agrees with that of the concordance \Lambda CDM model in the whole redshift domain and which is well approximated by the Einstein-de Sitter universe at and before decoupling. We determine the decoupling epoch in this LTB universe by Gamow's criterion and then calculate the positions of acoustic peaks. Thus obtained results are not consistent with the WMAP data. However, we find that one can fit the peak positions by appropriately modifying the LTB model, namely, by allowing the deviation of the distance-redshift relation from that of the concordance \Lambda CDM model at z>2 where no observational data are available at present. Thus there is still a possibility of explaining the apparent accelerated expansion of the universe by inhomogeneity without resorting to dark energy if we abandon the Copernican principle. Even if we do not take this extreme attitude, it also suggests that local, isotropic inhomogeneities around us may seriously affect the determination of the density contents of the universe unless the possible existence of such inhomogeneities is properly taken into account.

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Blobrana · L

Stirring a fresh debate over the composition of the universe, British physicists have claimed that dark matter and energy, the mysterious forces which are thought to make up 96 per cent of space, may not exist.
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Durham astronomers' doubts about the "Dark Side"

New research by astronomers in the Physics Department at Durham University suggests that the conventional wisdom about the content of the Universe may be wrong. Graduate student Utane Sawangwit and Professor Tom Shanks looked at observations from the Wilkinson Microwave Anisotropy Probe (WMAP) satellite to study the remnant heat from the Big Bang. The two scientists find evidence that the errors in its data may be much larger than previously thought, which in turn makes the standard model of the Universe open to question. The team publish their results in a letter to the journal Monthly Notices of the Royal Astronomical Society.
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Blobrana · L

Question: Is everything we know about the Universe wrong?

Two recent results published in MNRAS suggest that the answer to the above question, posed in a recent (17/3/10) BBC Horizon programme, is "Quite possibly!" Utane Sawangwit and Tom Shanks of Durham University are today suggesting in a Letter to MNRAS that the errors on the "gold standard" cosmic microwave background results from the WMAP satellite may be larger than previously supposed.
It is the pattern of ripples detected by microwave background telescopes such as WMAP that underpin the idea that the Universe is composed of 22% dark exotic particles and 74% dark energy with the remaining 4% being the atoms in the ordinary material that we see around us. This model produces a largest ripple size of about 1 degree on the microwave sky and this is well matched by the ripples seen in the WMAP data. So these WMAP ripples have a size that is roughly twice the size of the Full Moon as they appear on the sky. Models that don't have dark energy or dark matter tend to produce CMB ripples that are smaller, only about half the standard model size and so just about the size of the Full Moon.
Sawangwit and Shanks have used point-like radio sources to test how much the WMAP telescope smoothes these CMB ripples and have found evidence that this "beam smoothing" is much larger than suggested from WMAP's observations of the planet Jupiter. The radio sources have the advantage that they are much closer in brightness to the CMB ripples that are being studied than Jupiter which is ~1000 times brighter. But their faintness is also a disadvantage which means that the Durham team have had to stack hundreds of the radio sources to get their result. If the WMAP CMB map is smoothed by as much as the radio sources appear to be then it may make it more easy for other models without dark matter (or dark energy!) to fit the CMB data.
It will then be interesting to see if the new European PLANCK satellite, currently taking data, will confirm the WMAP results. The PLANCK telescope will also smooth the new CMB maps and again the radio source technique used by Sawangwit and Shanks can be used to help them judge how much.

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