web – A Darker View

KCWI Arrives on the Mountain

Keck Observatory is pushing the cutting edge of scientific discovery with the addition of the world’s most sensitive instrument for measuring the tendrils of faint gas in the intergalactic medium known as the cosmic web. The 5-ton instrument, the size of an ice cream truck, is named the Keck Cosmic Web Imager (KCWI). KCWI will uncover vital clues about the life-cycle of galaxies, helping to unravel mysteries about our universe.

KCWI being lifted off the trailer at Keck Observatory on the summit of Mauna Kea, Jan 20, 2017

Physics professor, Christopher Martin, and his team at Caltech, in collaboration with Keck Observatory, University of California Santa Cruz and industrial partners, designed and built the spectrograph to study the cosmic web in unprecedented detail. KCWI will enable astronomers to study many other exceedingly faint objects in the universe as well.

“For decades, astronomers have demonstrated that galaxies evolve. Now, we’re trying to figure out how and why,” says Martin, describing the potential of this instrument. “We know the gas around galaxies is ultimately fueling them, but it is so faint – we still haven’t been able to get a close look at it and understand how this process works.”

The design of KCWI is based on its predecessor, the Palomar Cosmic Web Imager. KCWI will be installed on one of the twin 10-meter Keck Observatory telescopes, the largest optical/infrared telescopes in the world. The telescopes’ location on Maunakea provides the most pristine viewing conditions in the world for this science. This unbeatable combination of technology and location will enable KCWI to provide some of the most-detailed glimpses of the universe ever, including the study of gas jets around young stars, the winds of dead stars and even supermassive black holes.

“The best location in the world for astronomy calls for the best tools for astronomy,” said Hilton Lewis, director of the Keck Observatory. “With KCWI on the world’s largest telescope, we are well positioned to develop our understanding of the evolution of galaxies by capturing high-resolution spectra of some of the faintest, most difficult to study objects in the universe in ways never before possible.”

KCWI arrived by ship from Los Angeles on January 20 and was carefully transported up to the observatory atop Maunakea. The instrument will be installed and tested, followed by the first observations in the coming months.

Scientists Build First Map of Hidden Universe

W. M. Keck Observatory press release…

A team led by astronomers from the Max Planck Institute for Astronomy has created the first three-dimensional map of the ‘adolescent’ Universe, just 3 billion years after the Big Bang. This map, built from data collected from the W. M. Keck Observatory, is millions of light-years across and provides a tantalizing glimpse of large structures in the ‘cosmic web’ – the backbone of cosmic structure.

On the largest scales, matter in the Universe is arranged in a vast network of filamentary structures known as the ‘cosmic web’, its tangled strands spanning hundreds of millions of light-years. Dark matter, which emits no light, forms the backbone of this web, which is also suffused with primordial hydrogen gas left over from the Big Bang. Galaxies like our own Milky Way are embedded inside this web, but fill only a tiny fraction of its volume.

Now a team of astronomers led by Khee-Gan Lee, a post-doc at the Max Planck Institute for Astronomy, has created a map of hydrogen absorption revealing a three-dimensional section of the universe 11 billions light years away – the first time the cosmic web has been mapped at such a vast distance. Since observing to such immense distances is also looking back in time, the map reveals the early stages of cosmic structure formation when the Universe was only a quarter of its current age, during an era when the galaxies were undergoing a major ‘growth spurt’.

The map was created by using faint background galaxies as light sources, against which gas could be seen by the characteristic absorption features of hydrogen. The wavelengths of each hydrogen feature showed the presence of gas at a specific distance from us. Combining all of the measurements across the entire field of view allowed the team a tantalizing glimpse of giant filamentary structures extending across millions of light-years, and paves the way for more extensive studies that will reveal not only the structure of the cosmic web, but also details of its function – the ways that pristine gas is funneled along the web into galaxies, providing the raw material for the formation of galaxies, stars, and planets.

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UCSC Scientists Capture First Cosmic Web Filaments at Keck Observatory

W. M. Keck Observatory press release…

Astronomers have discovered a distant quasar illuminating a vast nebula of diffuse gas, revealing for the first time part of the network of filaments thought to connect galaxies in a cosmic web. Researchers at the University of California, Santa Cruz, led the study, published January 19 in the journal, Nature.

Cosmic Web Filament — This deep image shows the nebula (cyan) extending across 2 million light-years that was discovered around the bright quasar UM287 (at the center of the image). Credit: S. Cantalupo, UCSC

Using the 10-meter Keck I telescope at the W. M. Keck Observatory in Hawaii, the researchers detected a very large, luminous nebula of gas extending about 2 million light-years across intergalactic space.

“This is a very exceptional object: it’s huge, at least twice as large as any nebula detected before, and it extends well beyond the galactic environment of the quasar,” said Sebastiano Cantalupo, first author of the paper and a postdoctoral fellow at UC Santa Cruz.

The standard cosmological model of structure formation in the universe predicts that galaxies are embedded in a cosmic web of matter, most of which (about 84 percent) is invisible dark matter. This web is seen in the results from computer simulations of the evolution of structure in the universe, which show the distribution of dark matter on large scales, including the dark matter halos in which galaxies form and the cosmic web of filaments that connect them. Gravity causes ordinary matter to follow the distribution of dark matter, so filaments of diffuse, ionized gas are expected to trace a pattern similar to that seen in dark matter simulations.

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