* Astronomy

Title: Ellipsoidal Universe Can Solve The CMB Quadrupole Problem
Authors: L. Campanelli, P. Cea, L. Tedesco

The recent three-year WMAP data have confirmed the anomaly concerning the low quadrupole amplitude compared to the best-fit Lambda CDM prediction. We show that, allowing the large-scale spatial geometry of our universe to be plane-symmetric with eccentricity at decoupling or order 10^-2, the quadrupole amplitude can be drastically reduced without affecting higher multipoles of the angular power spectrum of the temperature anisotropy.

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Title: The Sunyaev-Zel'dovich effect in a sample of 31 clusters - a comparison between the X-ray predicted and WMAP observed CMB temperature decrement
Authors: Richard Lieu, Jonathan P.D. Mittaz, Shuang-Nan Zhang

The WMAP Q, V, and W band radial profiles of temperature deviation of the cosmic microwave background (CMB) were constructed for a sample of 31 randomly selected nearby clusters of galaxies in directions of Galactic latitude |b| > 30°. The profiles were compared in detail with the expected CMB Sunyaev-Zel'dovich effect (SZE) caused by these clusters, with the hot gas properties of each cluster inferred observationally by applying gas temperatures as measured by ASCA to isothermal β models of the ROSAT X-ray surface brightness profiles, and with the WMAP point spread function fully taken into consideration. After co-adding the 31 cluster field, it appears that WMAP detected the SZE in all three bands. Quantitatively, however, the observed SZE only accounts for about 1/4 of the expected decrement. The discrepancy represents too much unexplained extra flux: in the W band, the detected SZE corresponds on average to 5.6 times less X-ray gas mass within a 10 arcmin radius than the mass value given by the ROSAT β model. We examined critically how the X-ray prediction of the SZE may depend on our uncertainties in the density and temperature of the hot intracluster plasma, and emission by cluster radio sources. Although our comparison between the detected and expected SZE levels is subject to a margin of error, the fact remains that the average observed SZE depth and profile are consistent with those of the primary CMB anisotropy, i.e. in principle the average WMAP temperature decrement among the 31 rich clusters is too shallow to accommodate any extra effect like the SZE. A unique aspect of this SZE investigation is that because all the data being analysed are in the public domain, our work is readily open to the scrutiny of others.

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The apparent absence of shadows where shadows were expected to be is raising new questions about the faint glow of microwave radiation once hailed as proof that the universe was created by a "Big Bang."

In a finding sure to cause controversy, scientists at University of Alabama Huntsville found a lack of evidence of shadows from "nearby" clusters of galaxies using new, highly accurate measurements of the cosmic microwave background.
A team of University of Alabama Huntsville scientists led by Dr. Richard Lieu, a professor of physics, used data from NASA's Wilkinson Microwave Anisotropy Probe (WMAP) to scan the cosmic microwave background for shadows caused by 31 clusters of galaxies.

"Among the 31 clusters that we studied, some show a shadow effect and others do not" - Dr. Richard Lieu.

If the standard Big Bang theory of the universe is accurate and the background microwave radiation came to Earth from the furthest edges of the universe, then massive X-ray emitting clusters of galaxies nearest our own Milky Way galaxy should all cast shadows on the microwave background.
These findings are scheduled to be published in the Sept. 1, 2006, edition of the Astrophysical Journal.

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Cosmic rays, which are high-energy atomic nuclei driven by spectacular cosmic events, come to us from every direction on the sky. Most of them are destroyed high in the atmosphere, creating a shower of high-speed particles that penetrate sky and earth with ease. Surprising results from Japan's Super-Kamiokande underground observatory have recently shown that the distribution of cosmic rays on the sky is not uniform, a useful clue to the nature of these cosmic voyagers.

Supernovae and similar high-energy events can accelerate protons and heavier atomic nuclei to enormous speeds, imparting a kinetic energy thousands of times greater than the mass of the particle itself. Many are much more powerful than anything our best particle accelerators can produce, so cosmic rays are of great interest to particle physicists as well as astronomers. The strongest (and rarest) cosmic rays can pack as much kinetic energy as a good punch in the jaw -- no mean feat for a subatomic particle weighing 10^27 times less than your fist!

For all their scientific potential, cosmic rays cannot be identified with any specific source. Because atomic nuclei are charged particles, they can be deflected by the Milky Way's magnetic field. While scientists have many ideas concerning the astronomical processes that can create cosmic rays, it has proven difficult to test these ideas.
What's more, most of the cosmic rays that meet the Earth never make it to the ground. Their annihilation in the atmosphere produces a “shower” of muons (heavy electrons, essentially), neutrinos, and other simple subatomic particles. Some of the by-products can produce showers of their own, eventually dissipating most of the cosmic ray's energy into the atmosphere. The high-energy muons, however, interact only rarely with matter and can slide through miles of atmosphere and bedrock before coming to a halt.

Lining the walls of this tank are 11,200 photo multiplier tubes, sensitive instruments that amplify the faintest glimmer of light into a strong electrical current. If an interesting event occurs anywhere in the tank's volume, the nature of the interaction can be reconstructed from the pattern of captured light on the walls. When supernova 1987a exploded in the Large Magellanic Cloud, for example, Super-Kamiokande captured a dozen neutrinos in two separate pulses from the dying star.

Cosmic muons in particular have a distinctive signature. While they travel at speeds close to that of light, light is about 75% slower in water than in air. The muons therefore move faster than the light they emit, so the leading edges of the emitted waves pile up into a bright, cone-shaped pulse. The same phenomenon can be seen in the powerful crest that defines the wake of a speedboat, or heard in the boom of a supersonic jet or rocket. When a cosmic muon passes through, the photo multipliers trace out a perfect ellipse or hyperbola (a conic section) on the wall.


Collecting over 200 million cosmic ray muons from five years of Super-Kamiokande data, researchers Gene Guillian, Yuichi Oyama, and other collaborators were able to reconstruct a full-sky map of the cosmic ray flux. Two features are readily apparent: an excess of cosmic rays in the direction of the constellation Taurus, and a deficit in the direction of Virgo. (The scale on the right is the ratio of local flux to average flux.)

The excess and deficit are both detected with a very high confidence; the probability for each to have been produced by random fluctuations is less than one in a million. Their amplitudes are also roughly the same, and they are separated by an angle of about 130° on the sky. This odd angle seems to preclude the most obvious explanation, that Super-K is seeing the effect of the Earth's motion with respect to an isotropic cosmic ray background. If such were the case, then the separation between the two features should be exactly 180°.

Oyama and Guillian offer another possible explanation. The cosmic ray excess points into the denser regions of our spiral arm of the Milky Way galaxy, and the deficit is pointing roughly out of the galactic plane. Does this result prove that some of the cosmic rays come from nearby sources?

“We have no idea about this” - Dr Yuichi Oyama.

Guillian's paper, for example, mentions a competing hypothesis: that local structure in the galactic magnetic field may focus or defocus the cosmic ray flux in certain directions.

These results provide an important clue to the origin of cosmic rays, and will certainly shed light on the question of how the galactic magnetic field influences their journey.

“In 1987, Kamiokande started an astronomy beyond light. In 2005, Super-Kamiokande started an astronomy beyond neutral particles ” Dr. Yuichi Oyama, (referring to the detection of supernova neutrinos mentioned above).


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