HST and 'dark matter' Options

[Guest_PhilCo126_*]

ASA Updates Plans for Hubble 'Ring Of Dark Matter' Briefing

GREENBELT, Md. - NASA will hold a media teleconference at 1 p.m. EDT on May 15 to discuss the strongest evidence to date that dark matter exists. This evidence was found in a ghostly ring of dark matter in the cluster CL0024+17, discovered using NASA's Hubble Space Telescope. The ring is the first detection of dark matter with a unique structure different from the distribution of both the galaxies and the hot gas in the cluster. The discovery will be featured in the June 20 issue of the Astrophysical Journal.

[Mongo]

Beating an increasingly dead horse here:

Vast Structure of Satellite Galaxies Discovered: Do the Milky Way’s Companions Spell Trouble for Dark Matter?

Astronomers from the University of Bonn in Germany have discovered a vast structure of satellite galaxies and clusters of stars surrounding our Galaxy, stretching out across a million light years. The work challenges the existence of dark matter, part of the standard model for the evolution of the universe.

In their effort to understand exactly what surrounds our Galaxy, the scientists used a range of sources from twentieth century photographic plates to images from the robotic telescope of the Sloan Deep Sky Survey. Using all these data they assembled a picture that includes bright 'classical' satellite galaxies, more recently detected fainter satellites and the younger globular clusters.

"Once we had completed our analysis, a new picture of our cosmic neighbourhood emerged," says Pawlowski. The astronomers found that all the different objects are distributed in a plane at right angles to the galactic disk. The newly-discovered structure is huge, extending from as close as 33,000 light years to as far away as one million light years from the centre of the Galaxy.

The various dark matter models struggle to explain this arrangement. "In the standard theories, the satellite galaxies would have formed as individual objects before being captured by the Milky Way," explains Kroupa. "As they would have come from many directions, it is next to impossible for them to end up distributed in such a thin plane structure."

Kroupa concludes by highlighting the wider significance of the new work. "Our model appears to rule out the presence of dark matter in the universe, threatening a central pillar of current cosmological theory. We see this as the beginning of a paradigm shift, one that will ultimately lead us to a new understanding of the universe we inhabit."

Link to original article: The VPOS: a vast polar structure of satellite galaxies, globular clusters and streams around the Milky Way

These findings demonstrate that a near-isotropic infall of cosmological sub-structure components onto the MW is essentially ruled out because a large number of infalling objects would have had to be highly correlated, to a degree not natural for dark matter sub-structures. The majority of satellites, streams and YH GCs had to be formed as a correlated population. This is possible in tidal tails consisting of material expelled from interacting galaxies. We discuss the tidal scenario for the formation of the VPOS, including successes and possible challenges. The potential consequences of the MW satellites being tidal dwarf galaxies are severe. If all the satellite galaxies and YH GCs have been formed in an encounter between the young MW and another gas-rich galaxy about 10-11 Gyr ago, then the MW does not have any luminous dark-matter substructures and the missing satellites problem becomes a catastrophic failure of the standard cosmological model.