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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First Light of Powerful New MOSFIRE Instrument

W. M. Keck Observatory press release

Engineers and astronomers are celebrating the much anticipated first light and first two nights commissioning of the MOSFIRE instrument, now installed on the Keck I telescope at W. M. Keck Observatory. MOSFIRE (Multi-Object Spectrometer For Infra-Red Exploration) will vastly increase the data gathering power of what is already the world’s most productive ground-based observatory.

“This is a near-infrared multi-object spectrograph, similar to our popular LRIS and DEIMOS instruments, only at longer wavelengths,” explained Keck Observatory Observing Support Manager Bob Goodrich. “The dedicated MOSFIRE project team members at Keck Observatory, Caltech, UCLA, and UC Santa Cruz are to be congratulated, as are the dedicated observatory operations staff who worked hard to get MOSFIRE integrated into the Keck I telescope and infrastructure. A lot of people have put in long hours getting ready for this momentous First Light.”

MOSFIRE First Light Image
First light with MOSFIRE, and unprocessed image of the interacting galaxies NGC4038 and NGC4039, credit: W. M. Keck Observatory

The first unprocessed image from MOSFIRE was made on the night of April 4, despite thick cirrus clouds over Mauna Kea. The subject was two interacting galaxies known as The Antennae. Additional images adn spectra were gathered on the night of April 5, as part of the continuing commissioning of the instrument.

MOSFIRE gathers spectra, which contain chemical signatures in the light of everything from stars to galaxies, at near-infrared wavelengths (that is, 0.97-2.45 microns, or millionths of a meter). Infrared is light which is beyond red in a rainbow—just beyond what human eyes can detect. Observing in the infrared allows researchers to penetrate cosmic dust clouds and see objects that are otherwise invisible, like the stars circling the supermassive black hole at the center of the Milky Way. It also allows for the study of the most distant objects, the light of which has been stretched beyond the red end of the spectrum by the expansion of the universe.

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MOSFIRE Arrives at Keck

W. M. Keck Observatory press release

A 10,000-pound package was delivered on Feb. 16 to the W. M. Keck Observatory near the summit of Mauna Kea. Inside is a powerful new scientific instrument that will dramatically increase the cosmic data gathering power of what is already the world’s most productive ground-based observatory.

The new instrument is called MOSFIRE (Multi-Object Spectrometer For Infra-Red Exploration). It is the newest tool to survey the cosmos and help astronomers learn more about star formation, galaxy formation and the early universe. The spectrometer was made possible through funding provided by the National Science Foundation and a generous donation from astronomy benefactors Gordon and Betty Moore.

“This is a crucial and important step,” said MOSFIRE co-principal investigator Ian McLean of U.C. Los Angeles, who has been involved in the building of four instruments for the Keck telescopes. “Just shipping it to Hawaii is the first step.” A long series of installation steps are already underway that will lead up to MOSFIRE’s “first light” on the sky and handover to the Keck community in August.

Hauling MOSFIREThe truck carrying MOSFIRE was escorted by police, Mauna Kea rangers and Keck Observatory personnel as it climbed the last few thousand feet to the summit. Photo by Larry O’Hanlon

MOSFIRE will gather spectra—chemical signatures in the rainbows of light from everything from stars to galaxies—at near-infrared wavelengths (0.97-2.45 microns, or millionths of a meter). That’s light which is beyond the red end of a rainbow—just a bit longer wavelength than human eyes can see. Observing in the infrared allows researchers to penetrate clouds of dust to see objects that are otherwise obscured. It also allows for the study of the most distant objects, the spectra of which have been stretched beyond optical wavelengths by the expansion of the universe.

What sets MOSFIRE apart from other instruments is its vastly more light-sensitive camera and its ability to survey up to 46 objects at once then switch targets in just minutes – an operation that takes comparable infrared instruments one to two days to complete.

“I reckon that MOSFIRE will observe very faint targets more than a hundred times faster than has ever been possible,” says Caltech astronomer Chuck Steidel, MOSFIRE’s co-principal investigator. “All the observations that my group and I have done in near-infrared spectroscopy with Keck over the last ten years could be done in just one night with MOSFIRE.”

Steidel anticipates that MOSFIRE will be one of the Keck’s workhorse instruments, used for about half of all telescope time on the Keck I Telescope. “It’s opening up a whole new area of study.”

Another big asset of MOSFIRE is that it can scan the sky with a 6.1 arc minute field of view, which is about 20 percent of a full moon and nearly 100 times bigger than the Keck’s current near-infrared camera. To take spectra of multiple objects, the state-of-the-art spectrometer consists of 46 pairs of sliding bars that open and close like curtains. Aligned in rows, each pair of bars blocks most of the sky, leaving a small slit between the bars which allow a sliver of light from the targeted object to leak through. Light from each slit then enters the spectrometer, which breaks down the object’s light into its spectrum of wavelengths.

MOSFIREMark Kassis stands beside the MOSFIRE spectrograph

Because everything that’s even somewhat warm radiates in the infrared, all infrared instruments must be kept cold to prevent any trace of heat from the ground, the telescope, or the instrument itself from messing up the signal from space, MOSFIRE is kept at a cool 120 Kelvins (about -243 degrees Fahrenheit or -153 degrees Celsius). This makes MOSFIRE the largest cryogenic instrument on the Keck telescopes.

Astronomers will use MOSFIRE to study the epoch of galaxy formation, as well as the so-called period of re-ionization, when the universe was just a half-billion to a billion years old. The instrument will also be used to investigate nearby stars, young stars, how stars formed, and even brown dwarfs, which are stars not quite massive enough for nuclear fusion to ignite in their cores.

MOSFIRE will also allow astronomers to do riskier—but more scientifically rewarding—research, Steidel says. Taking the spectrum of a single star or galaxy involves precious telescope time and resources. But because MOSFIRE can observe many objects at once, astronomers can afford to take extremely long exposures. Otherwise, such long exposures of single targets would be difficult to justify with limited telescope time and other observing targets waiting in line.

Caltech’s Keith Matthews, who has built two previous Keck instruments, plays a leading role as chief instrument scientist. The team includes the engineering and technical staff of W. M. Keck Observatory, the technical staff of the UCLA Infrared Lab, optical designer Harland Epps of UC Santa Cruz and the staff of Caltech Optical Observatories.

The Flight of OSIRIS

An incredible amount of planning and work went into the job, with everything culminating in a few days of frenetic activity. Often referred to as “twins”, the Keck telescopes seem anything but. Over the years these once identical twins have taken on their own characteristics. One of the things that differentiates the two, each has its own set of unique instruments. Cameras and spectrographs, these multimillion dollar devices allow the recording and studying of the light collected by the massive 10-meter mirrors. This week we moved one of these instruments from Keck 2 to Keck 1… OSIRIS.

OSIRIS is an infrared integral field spectrograph. Designed to take full advantage of the Keck Adaptive Optics systems, the instrument has a relatively small field of view. Within that small field it does amazing things, providing a simultaneous spectrum and image of an object. Essentially it takes a stack of images at the same time, each at a different wavelength. This gives astronomers a very powerful tool. One image will show the distribution of particular elements throughout an object. Using doppler shift, an astronomer can also observe how everything is moving within the object as well.

Lowering OSIRIS into Keck 1 AO
The Keck crew lowering OSIRIS into Keck 1 AO

Moving an instrument is not a trivial job. It is not simply a matter of unplugging the instrument and moving it to the other telescope. Each instrument has a tremendous amount of infrastructure required to support it. Electrical wiring, optical fibers, plumbing for the cooling systems, support computers, and more… All of it has to be moved.

OSIRIS has been a removable instrument, mounted to a handling cart for easy removal and installation into the telescope. The new installation will be a permanent mount within the AO enclosure. A new mount must be designed and fabricated. New support beams welded and bolted into place. There are openings to be cut into the floor for the mounts and support connections. Then all of the electrical, optical cabling and plumbing run through the structure of the telescope. This all has to be designed, reviewed and then the modifications performed without interfering with nightly observing. The amount of work is truly daunting, and thanks to the efforts of a great crew, now complete.

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Atop the Weather Mast

I got lucky.

Weather Mast
The author working on the Keck weather mast
I had expected it to be a day of 20mph winds and freezing temperatures. What I got was a balmy 11°C (52°F) and just a gentle breeze. All for the good as I planned to spend several hours hanging off the weather mast installing wiring to improve the new dew point sensor. A cold wind can quickly turn the roof of the observatory into a miserable place.

The original sensor housing had proved to be vulnerable to heavy icing. The new housing should be more resilient, as well as providing better daytime temperature readings. This is due to changing to a different shelter design that uses a fan to move air through the housing past the sensor. I also modified the housing with the addition of a heating element to allow de-icing.

Weather mast covered with several inches of ice
The Keck weather mast covered with several inches of ice
To make the heating element I needed heavy nichrome wire. Not having any on hand I took a trip to the thrift shop. There I bought a used toaster for a couple dollars and spent an hour dismantling the toaster to remove the heating elements. I took the wire and wrapped it through the interior of the instrument housing, creating a heating element that should work quite nicely with a 12V supply, gently warming the housing and melting any ice.

A beautiful day on the summit, nice to spend a few hours atop the roof, hanging in a safety harness from the weather mast. I even remembered to put on some sunscreen to avoid frying in the high altitude sunlight. A new cable pulled through the conduit, the instrument shelter replaced, a little further wiring inside and the job was done. I will have to await another round of bad weather to see if the changes work, but given the trend this winter, I will not have to wait long.