More than half of the largest galaxies in the nearby universe have collided and merged with another galaxy in the past two billion years, according to a Yale astronomer in a study using hundreds of images from two of the deepest sky surveys ever conducted.
The panels show several of the newly found galaxy collisions in the nearby universe, using the NOAO Deep Wide-Field Survey (NDWFS) and the Multiwavelength Survey by Yale/Chile (MUSYC). The collisions (occurring in different galaxy pairs) are seen in different stages of the merger process, which taken together show the sequence that occurs. In (a) and (b) [top left and top right], the galaxies are still separated, but huge tidal forces of gravity are already at work pulling stars from the galaxies into enormous broad fans that stretch hundreds of thousands of light-years in space.
In (c) and (d) [bottom left and bottom right], the colliding galaxies have merged into single, larger galaxies. The violent past of these galaxies can be inferred from the tidal "debris" that still surrounds the newly formed galaxies. Images (a), (b), and (d) are from the NDWFS; image (c) is from MUSYC. Credit: P. van Dokkum/Yale University and NOAO/AURA/NSF
The idea of large galaxies being assembled primarily by mergers rather than evolving by themselves in isolation has grown to dominate cosmological thinking. However, a troubling inconsistency within this general theory has been that the most massive galaxies appear to be the oldest, leaving minimal time since the Big Bang for the mergers to have occurred.
"Our study found these common massive galaxies do form by mergers. It is just that the mergers happen quickly, and the features that reveal the mergers are very faint and therefore difficult to detect," said Pieter van Dokkum , assistant professor of astronomy at Yale University, and sole author of the paper appearing in the December 2005 issue of the Astronomical Journal.
Janet Rettig Emanuel | EurekAlert!
Significantly more productivity in USP lasers
06.12.2016 | Fraunhofer-Institut für Lasertechnik ILT
Shape matters when light meets atom
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In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
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The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
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