Seven years of meticulous observing have resulted in a cosmic discovery that comes from an era dating back 13.1 billion years, giving scientists a detailed glimpse of what may have happened just after the Big Bang.
Using the world-class W. M. Keck Observatory on Maunakea, Hawaii, an international team of astronomers from the United States, Australia, and Europe has confirmed the existence of one of the most distant galaxies in the universe.
To characterize the faint galaxy, the discovery team, led by Austin Hoag, a University of California, Davis physics graduate student, used MOSFIRE, the most in-demand instrument on the 10-meter Keck I telescope.
What makes this galaxy extraordinary is that it is ordinary. It is thought to be a common galaxy at that distance and age of the universe. However, such galaxies would normally be too faint to detect. The astronomers used a method called gravitational lensing to magnify the galaxy so they could study it.
“Most objects that we’ve seen at that distance are extremely bright, and probably rare compared to other galaxies,” said Hoag. “We think this galaxy is much more representative of other galaxies of its time.”
An international team of astrophysicists led by Benny Trakhtenbrot, a researcher at ETH Zurich’s Institute for Astronomy, discovered a gigantic black hole in an otherwise normal galaxy, using W. M. Keck Observatory’s 10-meter, Keck I telescope in Hawaii. The team, conducting a fairly routine hunt for ancient, massive black holes, was surprised to find one with a mass of more than 7 billion times our Sun making it among the most massive black holes ever discovered. And because the galaxy it was discovered in was fairly typical in size, the study calls into question previous assumptions on the development of galaxies. Their findings are being published today in the journal Science.
The data, collected with Keck Observatory’s newest instrument called MOSFIRE, revealed a giant black hole in a galaxy called CID-947 that was 11 billion light years away. The incredible sensitivity of MOSFIRE coupled to the world’s largest optical/infrared telescope meant the scientists were able to observe and characterize this black hole as it was when the Universe was less than two billion years old, just 14 percent of its current age (almost 14 billion years have passed since the Big Bang).
Even more surprising than the black hole’s record mass, was the relatively ordinary mass of the galaxy that contained it.
Most galaxies host black holes with with masses less than one percent of the galaxy. In CID-947, the black hole mass is 10 percent that of its host galaxy. Because of this remarkable disparity, the team deduced this black hole grew so quickly the host galaxy was not able to keep pace, calling into question previous thinking on the co-evolution of galaxies and their central black holes.
Keck again holds the record, for the moment at least, of the farthest galaxy ever observed. It is a record that we have been passing back and forth with the neighboring Subaru Telescope for some years now. We currently have the advantage of MOSFIRE, a fantastic spectrograph to discover these objects. I expect our hold on this title will be transitory, there are candidate objects that may even be somewhat further away and back in time.
Why try to observe these galaxies? They tell us a great deal about the formation of the first stars and galaxies after what astronomers call the “Dark Ages”, a period of time after the Big Bang when light could not travel through the galaxy, absorbed by a fog of neutral hydrogen. These first stars and galaxies ionized this hydrogen, creating the transparent universe we see today. By studying these galaxies we learn a great deal about how the universe we see today came to be.
An international team of astronomers, led by Yale and the University of California, Santa Cruz, pushed back the cosmic frontier of galaxy exploration to a time when the Universe was only five percent of its present age. The team discovered an exceptionally luminous galaxy more than 13 billion years in the past and determined its exact distance from Earth using the powerful MOSFIRE instrument on the 10-meter Keck I telescope at the W. M. Keck Observatory in Hawaii. These observations confirmed it to be the most distant galaxy ever measured, setting a new record. The findings are being published in Astrophysical Journal Letters today.
University of Texas at Austin astronomer Steven Finkelstein has led a team that has discovered and measured the distance to the most distant galaxy ever found, using the W. M. Keck Observatory on the summit of Mauna Kea, Hawaii. The galaxy is seen as it was at a time just 700 million years after the Big Bang. The result will be published in the Oct. 24 issue of the journal Nature.
Initial observations from NASA’s Hubble Space Telescope identified many candidates for galaxies in the early universe, but this galaxy is the earliest and most distant definitively confirmed, using the 10-meter, Keck I telescope fitted with Keck Observatory’s newest instrument, MOSFIRE.
What makes this distance so exciting, is “we get a glimpse of conditions when the universe was only about 5 percent of its current age of 13.8 billion years,” said Casey Papovich of Texas A&M University, second author of the study.
Astronomers can study how galaxies evolve because light travels at a finite speed, about 186,000 miles per second. Thus when we look at distant objects, we see them as they appeared in the past. The farther astronomers can push their observations, the farther into the past they can see.
“We want to study very distant galaxies to learn how they change with time,” Finkelstein said. “This helps us understand how the Milky Way came to be.”
The devil is in the details, however, when it comes to making conclusions about galaxy evolution, which means astronomers must employ the most rigorous methods and utilize the most powerful instruments to measure the distances to these galaxies in order to understand at what epoch of the universe they are seen.
The Hubble CANDELS survey uses colors from HST images to identify potentially distant galaxies. Finkelstein’s team selected z8_GND_5296, and dozens of others, for follow-up spectroscopy from the approximately 100,000 CANDELS galaxies. This method is good, but not foolproof, Finkelstein says. Using colors to sort galaxies is tricky because more nearby objects can masquerade as distant galaxies.
In order to accurately determine the distance to these galaxies, astronomers use spectroscopy to measure how much a galaxy’s light wavelengths have shifted toward the red end of the spectrum over their travels from the galaxy to Earth. This phenomenon is called “redshift”, and is due the expansion of the universe.
The team used Keck Observatory’s Keck I telescope in Hawaii, one of the two largest optical/infrared telescopes in the world, to measure the redshift of z8_GND_5296 at 7.51, the highest galaxy redshift ever confirmed. The redshift means this galaxy hails from a time only 700 million years after the Big Bang.
Keck I was fitted with the new MOSFIRE instrument, which made the measurement possible, Finkelstein said. “The instrument is great. Not only is it sensitive, it can look at multiple objects at a time,” he said, which allowed his team to observe 43 galaxies in only two nights at Keck Observatory, and obtain the highest quality observations possible.
In addition to its great distance, the team’s observations showed that the galaxy z8_GND_5296 is forming stars extremely rapidly — producing stars at a rate 150 times faster than our own Milky Way galaxy. This new distance record-holder lies in the same part of sky as the previous record-holder (redshift 7.2), which also happens to have a very high rate of star-formation.
“So we’re learning something about the distant universe,” Finkelstein said. “There are way more regions of very high star formation than we previously thought. … There must be a decent number of them if we happen to find two in the same area of the sky.”
In addition to their studies with Keck, the team also observed z8_GND_5296 in the infrared with NASA’s Spitzer Space Telescope. Spitzer measured how much ionized oxygen the galaxy contains, which helps pin down the rate of star formation. The Spitzer observations also helped rule out other types of objects that could masquerade as an extremely distant galaxy, such as a more nearby galaxy that is particularly dusty.
Other team members include Bahram Mobasher of the University of California, Riverside; Mark Dickinson of the National Optical Astronomy Observatory; Vithal Tilvi of Texas A&M; and Keely Finkelstein and Mimi Song of UT-Austin.
Join the W. M. Keck Observatory for an evening of astronomy presented at the Kahilu Theater.
MOSFIRE is the newest and the most advanced astronomical instrument available today. Dr. Ian McLean from UCLA will describe some of the technical challenges developing and commissioning this multi-year, multi-million dollar instrument. He will also share early science results ranging from the discovery of ultra-cool, nearby substellar mass objects, to the detection of oxygen in young galaxies only 2 billion years after the Big Bang.
Wednesday, May 22, 2013
Show starts at 7 p.m.
Free and Open to the Public
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.”
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.
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.
The 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.
Mark 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.