“The farther we look back into space the farther we see back in time,” explained Rauch.” We were actually trying to measure a faint signal from intergalactic gas caused by the cosmic ultraviolet background radiation. But as often happens in science, we got a surprise and found something we weren't looking for—dozens of faint, discrete objects emitting radiation from neutral hydrogen in the so-called Lyman alpha line, a fundamental signature of protogalaxies.”
The team used the European Southern Observatory's Very Large Telescope, for an unprecedented 92 hours, to expose a spectrum of the universe when it was only 2 billion years old. Most astronomers believe that when the universe was young it was filled with a thin, almost uniform gas. A popular theory of galaxy formation predicts that the gas accreted forming smaller protogalaxies, which then collided and merged to become the massive galaxies seen today. The new discovery lends strong support to this theory.
During the 1990s there was mounting evidence in favor of this hierarchical picture of galactic evolution, including measurements of distant quasars by Rauch and collaborators that showed how the properties of cosmic gas clouds—the reservoir of matter for galaxy formation—fit within that scheme.
“Most of those gas clouds are dark and visible only as foreground objects, which cast something of a shadow against a bright background quasar,” Becker said. “Intriguingly, one class of these shadows—known as damped Lyman alpha systems—was suspected to arise when those small, protogalactic building blocks intersect the line-of-sight to the quasar. For many years, these shadows were our only hint that a population of numerous early galaxies existed.”
Until now this possibility could not be tested because these protogalaxies, with their low masses and tiny stellar populations, were too faint for observations. The weak light signal that the team has now detected from these objects implies low star formation rates and a still small amount of chemical enrichment, as expected for young galaxies. The objects are about 20 times more common than all the distant galaxies ever seen from ground-based surveys, a finding consistent with the properties of the puzzling damped Lyman alpha shadows and with the abundance of early low-mass protogalaxies in the hierarchical picture.
Significantly more productivity in USP lasers
06.12.2016 | Fraunhofer-Institut für Lasertechnik ILT
Shape matters when light meets atom
05.12.2016 | Centre for Quantum Technologies at the National University of Singapore
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.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
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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