W. M. Keck Observatory Achieves First Light with New Instrument

W. M. Keck Observatory press release

W. M. Keck Observatory overnight captured the very first successful science data from its newest, cutting-edge instrument, the Keck Cosmic Web Imager (KCWI).

KCWI First Light Image
KCWI’s first look at the cosmos involved a spectral image of an exquisitely dense core of an ancient astronomical relic, showcasing the highest spectral resolving power and spatial resolution of the instrument. Credit W. M. Keck Observatory
KCWI captures three-dimensional data, as opposed to the traditional two-dimensional image or spectrum of conventional instruments. In a single observation, it records an image of the object at multiple wavelengths allowing scientists to explore both the spatial dimension (as in an image) and the spectral dimension (or color) of an object.

“I’m thrilled to see this new instrument,” said Keck Observatory Director Hilton Lewis. “It takes years to design and build these very sophisticated instruments. KCWI is a superb example of the application of the most advanced technology to enable the hardest science. I believe it has the potential to transform the science that we do, and continue to keep Keck Observatory right at the forefront of astronomical research.”

KCWI is extremely sensitive, specifically designed to capture high-resolution spectra of ultra-faint celestial bodies with unprecedented detail. It is able to differentiate even the slightest changes in spectral color with a great degree of accuracy.

This powerful capability is key for astronomers because a highly-detailed spectral image allows them to identify a cosmic object’s characteristics, including its temperature, motion, density, mass, distance, chemical composition, and more.

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KCWI Arrives on the Mountain

W. M. Keck Observatory News Release

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
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.

Cosmic Web Imager Coming to Keck

Caltech press release

Caltech astronomers have taken unprecedented images of the intergalactic medium (IGM)—the diffuse gas that connects galaxies throughout the universe—with the Cosmic Web Imager, an instrument designed and built at Caltech. Until now, the structure of the IGM has mostly been a matter for theoretical speculation. However, with observations from the Cosmic Web Imager, deployed on the Hale 200-inch telescope at Palomar Observatory, astronomers are obtaining our first three-dimensional pictures of the IGM. The Cosmic Web Imager will make possible a new understanding of galactic and intergalactic dynamics, and it has already detected one possible spiral-galaxy-in-the-making that is three times the size of our Milky Way.

Lyman Alpha Blob
Comparison of Lyman alpha blob observed with Cosmic Web Imager and a simulation of the cosmic web based on theoretical predictions.
Credit: Christopher Martin, Robert Hurt
The Cosmic Web Imager was conceived and developed by Caltech professor of physics Christopher Martin. “I’ve been thinking about the intergalactic medium since I was a graduate student,” says Martin. “Not only does it comprise most of the normal matter in the universe, it is also the medium in which galaxies form and grow.”

Since the late 1980s and early 1990s, theoreticians have predicted that primordial gas from the Big Bang is not spread uniformly throughout space, but is instead distributed in channels that span galaxies and flow between them. This “cosmic web”—the IGM—is a network of smaller and larger filaments crisscrossing one another across the vastness of space and back through time to an era when galaxies were first forming and stars were being produced at a rapid rate.

Martin describes the diffuse gas of the IGM as “dim matter,” to distinguish it from the bright matter of stars and galaxies, and the dark matter and energy that compose most of the universe. Though you might not think so on a bright sunny day or even a starlit night, fully 96 percent of the mass and energy in the universe is dark energy and dark matter (first inferred by Caltech’s Fritz Zwicky in the 1930s), whose existence we know of only due to its effects on the remaining 4 percent that we can see: normal matter. Of this 4 percent that is normal matter, only one-quarter is made up of stars and galaxies, the bright objects that light our night sky. The remainder, which amounts to only about 3 percent of everything in the universe, is the IGM.

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