Posts tagged Big Bang
CU study: ‘Sideline quasars’ helped to stifle early galaxy formation
Mar 21st
CU-Boulder Professor Michael Shull and Research Associate David Syphers used the Hubble Space Telescope to look at the quasar — the brilliant core of an active galaxy that acted as a “lighthouse” for the observations — to better understand the conditions of the early universe. The scientists studied gaseous material between the telescope and the quasar with a $70 million ultraviolet spectrograph on Hubble designed by a team from CU-Boulder’s Center for Astrophysics and Space Astronomy.
During a time known as the “helium reionization era” some 11 billion years ago, blasts of ionizing radiation from black holes believed to be seated in the cores of quasars stripped electrons from primeval helium atoms, said Shull. The initial ionization that charged up the helium gas in the universe is thought to have occurred sometime shortly after the Big Bang.
“We think ‘sideline quasars’ located out of the telescope’s view reionized intergalactic helium gas from different directions, preventing it from gravitationally collapsing and forming new generations of stars,” he said. Shull likened the early universe to a hunk of Swiss cheese, where quasars cleared out zones of neutral helium gas in the intergalactic medium that were then “pierced” by UV observations from the space telescope.
The results of the new study also indicate the helium reionization era of the universe appears to have occurred later than thought, said Shull, a professor in CU-Boulder’s astrophysical and planetary sciences department. “We initially thought the helium reionization era took place about 12 billion years ago,” said Shull. “But now we think it more likely occurred in the 11 to 10 billion-year range, which was a surprise.”
A paper on the subject by Shull and Syphers was published online this week in the Astrophysical Journal.
The Cosmic Origins Spectrograph used for the quasar observations aboard Hubble was designed to probe the evolution of galaxies, stars and intergalactic matter. The COS team is led by CU Professor James Green of CASA and was installed on Hubble by astronauts during its final servicing mission in 2009. COS was built in an industrial partnership between CU and Ball Aerospace & Technologies Corp. of Boulder.
“While there are likely hundreds of millions of quasars in the universe, there are only a handful you can use for a study like this,” said Shull. Quasars are nuclei in the center of active galaxies that have “gone haywire” because of supermassive black holes that gorged themselves in the cores, he said. “For our purposes, they are just a really bright background light that allows us to see to the edge of the universe, like a headlight shining through fog.”
The universe is thought to have begun with the Big Bang that triggered a fireball of searing plasma that expanded and then become cool neutral gas at about 380,000 years, bringing on the “dark ages” when there was no light from stars or galaxies, said Shull. The dark ages were followed by a period of hydrogen reionization, then the formation of the first galaxies beginning about 13.5 billion years ago. The first galaxies era was followed by the rise of quasars some 2 billion years later, which led to the helium reionization era, he said.
The radiation from the huge quasars heated the gas to 20,000 to 40,000 degrees Fahrenheit in intergalactic realms of the early universe, said Shull. “It is important to understand that if the helium gas is heated during the epoch of galaxy formation, it makes it harder for proto-galaxies to hang on to the bulk of their gas. In a sense, it’s like intergalactic global warming.”
The team is using COS to probe the “fossil record” of gases in the universe, including a structure known as the “cosmic web” believed to be made of long, narrow filaments of galaxies and intergalactic gas separated by enormous voids. Scientists theorize that a single cosmic web filament may stretch for hundreds of millions of light years, an eye-popping number considering that a single light-year is about 5.9 trillion miles.
COS breaks light into its individual components — similar to the way raindrops break sunlight into the colors of the rainbow — and reveals information about the temperature, density, velocity, distance and chemical composition of galaxies, stars and gas clouds.
For the study, Shull and Syphers used 4.5 hours of data from Hubble observations of the quasar, which has a catalog name of HS1700+6416. While some astronomers define quasars as feeding black holes, “We don’t know if these objects feed once, or feed several times,” Shull said. They are thought to survive only a few million years or perhaps a few hundred million years, a brief blink in time compared to the age of the universe, he said.
“Our own Milky Way has a dormant black hole in its center,” said Shull. “Who knows? Maybe our Milky Way used to be a quasar.”
The first quasar, short for “quasi-stellar radio source,” was discovered 50 years ago this month by Caltech astronomer Maarten Schmidt. The quasar he observed, 3C-273, is located roughly 2 billion years from Earth and is 40 times more luminous than an entire galaxy of 100 billion stars. That quasar is receding from Earth at 15 percent of the speed of light, with related winds blowing millions of miles per hour, said Shull.
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Young galaxies are 13-billion light years from home
Jan 10th
DEVELOPING GALAXY CLUSTER EVER FOUND
A team of researchers led by the University of Colorado Boulder has used NASA’s Hubble Space Telescope to uncover a cluster of galaxies in the initial stages of construction — the most distant such grouping ever observed in the early universe.
In a random sky survey made in near-infrared light, Hubble spied five small galaxies clustered together 13.1 billion light-years away. They are among the brightest galaxies at that epoch and very young, living just 600 million years after the universe’s birth in the Big Bang. One light-year is about 6 trillion miles.
Galaxy clusters are the largest structures in the universe, comprising hundreds to thousands of galaxies bound together by gravity. The developing cluster, or protocluster, presumably will grow into one of today’s massive galactic “cities” comparable to the nearby Virgo cluster, a collection of more than 2,000 galaxies.
The composite image at right, taken in visible and near-infrared light, reveals the location of five tiny galaxies clustered together 13.1 billion light-years away. The circles pinpoint the galaxies. The Wide Field Camera 3 aboard NASA’s Hubble Space Telescope spied the galaxies in a random sky survey. The developing cluster is the most distant ever observed. The young galaxies lived just 600 million years after the universe’s birth in the Big Bang. The average distance between them is comparable to that of the galaxies in the Local Group, consisting of two large spiral galaxies, the Milky Way and Andromeda, and a few dozen small dwarf galaxies. The close-up images at right, taken in near-infrared light, show the puny galaxies. The letters “a” through “e” correspond to the galaxies’ location in the wide-field view at left. Simulations show that the galaxies will eventually merge and form the brightest central galaxy in the cluster, a giant elliptical similar to the Virgo cluster’s M87. Galaxy clusters are the largest structures in the universe, comprising hundreds to thousands of galaxies bound together by gravity. The developing cluster presumably will grow into a massive galactic city, similar in size to the nearby Virgo cluster, a collection of more than 2,000 galaxies. Credit: NASA, ESA, M. Trenti (University of Colorado Boulder and Institute of Astronomy, University of Cambridge, U.K.), L. Bradley (Space Telescope Science Institute, Baltimore), and the BoRG team
or more information on the galaxies visit the news center at http://hubblesite.org/.
“These galaxies formed during the earliest stages of galaxy assembly, when galaxies had just started to cluster together,” says the study’s leader, Michele Trenti, a research associate at CU-Boulder’s Center for Astrophysics and Space Astronomy and a newly appointed scientist at the Institute of Astronomy at the University of Cambridge in the United Kingdom. “The result confirms our theoretical understanding of the buildup of galaxy clusters. And Hubble is just powerful enough to find the first examples of them at this distance.”
Trenti will present his results Jan. 10 at the American Astronomical Society meeting in Austin, Texas. The study will appear in the Feb. 10 issue of The Astrophysical Journal.
Most galaxies in the universe live in groups and clusters, and astronomers have probed many mature “galactic cities” in detail as far as 11 billion light-years away. But finding clusters in the early phases of construction has been challenging because they are rare, dim and widely scattered across the sky.
“Records are always exciting, and this is the earliest and the most distant developing galaxy cluster that has ever been seen,” said CU-Boulder Professor Michael Shull of the astrophysical and planetary sciences department, a member of the observing team. “We have seen individual galaxies this old and far away, but we have not seen groups of them in the construction process before.”
Last year, a group of astronomers uncovered one distant developing cluster. Led by Peter L. Capak of NASA’s Spitzer Science Center at the California Institute of Technology in Pasadena, the astronomers discovered a galactic grouping 12.6 billion light-years away with a variety of telescopes, including Hubble. Spectroscopic observations were made with the W.M. Keck Observatory in Hawaii to confirm the cluster’s distance by measuring how much its light has been stretched by the expansion of space.
Trenti’s team used the sharp-eyed Wide Field Camera 3 to hunt for the elusive catch. “We need to look in many different areas because the odds of finding something this rare are very small,” Trenti said. “It’s like playing a game of Battleship: The search is hit and miss. Typically a region has nothing, but if we hit the right spot we can find multiple galaxies.”
Because these distant, fledgling clusters are so dim, the team hunted for the systems’ brightest galaxies. These bright lights act as billboards, advertising cluster construction zones, according to the team. Galaxies at early epochs don’t live alone. From simulations, the astronomers expect galaxies to be clustered together.
Because brightness correlates with mass, the most luminous galaxies pinpoint the location of developing clusters. These powerful light beacons live in deep wells of dark matter, which form the underlying structure in which galaxy clusters form, Trenti said. The team expects many fainter galaxies that were not seen in these observations to inhabit the same neighborhood.
The five bright galaxies spotted by Hubble are about one-half to one-tenth the size of our Milky Way, yet are comparable in brightness. The galaxies are bright and massive because they are being fed lots of gas through mergers with other galaxies, Trenti said. The team’s simulations show that the galaxies will eventually merge and form the brightest central galaxy in the cluster, a giant elliptical similar to the Virgo Cluster’s M87.
The observations demonstrate the progressive buildup of galaxies and provide further support for the hierarchical model of galaxy assembly, in which small objects accrete mass, or merge, to form bigger objects over a smooth and steady but dramatic process of collision and agglomeration. Astronomers have likened the process to streams merging into tributaries, then into rivers and to a bay.
Hubble looked in near-infrared light because ultraviolet and visible light from distant objects have been stretched into near-infrared wavelengths by the expansion of space in these extremely distant galaxies. The observations are part of the Brightest of Reionizing Galaxies or BoRG survey, which is using Hubble’s Wide Field Camera 3 to search for the brightest galaxies around 13 billion years ago, when light from the first stars burned off a fog of cold hydrogen in a process called reionization.
The team estimated the distance to the newly spied galaxies based on their colors, but the astronomers plan to follow up with spectroscopic observations to confirm their distance.
Without spectroscopic observations, it’s not clear whether the observed galaxies are gravitationally bound yet. The average distance between them is likely comparable to that of the galaxies in the Local Group, consisting of two large spiral galaxies, the Milky Way and Andromeda, and a few dozen small dwarf galaxies.
These observations are pushing Hubble to the limit of its ability. This region, however, will be prime country for future telescopes such as NASA’s James Webb Space Telescope, an infrared observatory scheduled to launch later this decade. Webb will see farther into the infrared, allowing it to hunt for even earlier stages of galaxy assembly within 300 million years of the Big Bang.
Shull, also a faculty member at CU-Boulder’s Center for Astrophysics and Space Astronomy, said the research team will receive an additional 260 orbits of observation time on Hubble to continue the search for more of the fledgling galaxy clusters as part of the BoRG survey. “There is high interest right now in learning if Earth is unique in the universe in its ability to host life,” he said. “Similarly, we are interested to see if these ancient, forming galaxy clusters we have identified are unique, or if there are others out there. I expect that we may find a few more.”
The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute, or STScI, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy Inc., in Washington, D.C.
For more information on the galaxies visit the news center at http://hubblesite.org/. For more information on CU-Boulder’s CASA visit http://casa.colorado.edu/.
For more information on CU-Boulder’s CASA visit http://casa.colorado.edu/.
CU-BOULDER PART OF INTERNATIONAL TEAM TO DISCOVER NEUTRINOS CAN CHANGE ‘FLAVORS’
Jun 15th
An international research team led by Japan and including the University of Colorado Boulder may have taken a significant step in discovering why matter trumped antimatter at the time of the Big Bang, helping to create virtually all of the galaxies and stars in the universe.
The experiment, known as the Tokai to Kamioka experiment, or T2K, included shooting a beam of neutrinos underground from the Japan Proton Accelerator Research Complex, or J-PARC, on the country’s east coast to a detector near Japan’s west coast, a distance of about 185 miles. Elementary particles that are fundamental building blocks of nature, neutrinos generally travel at the speed of light and can pass through ordinary matter, like Earth’s crust, with ease. Neutrinos come in three types: muon, electron and tau.
The T2K team discovered that muon neutrinos can spontaneously change their “flavor” to electron neutrinos, a finding that may help explain why the universe is made up mostly of matter rather than antimatter, said CU-Boulder Assistant Professor Alysia Marino of the physics department, who is part of a university contingent that participated in the experiment. Scientists had previously measured the change of muon neutrinos to tau neutrinos and electron neutrinos to muon neutrinos or tau neutrinos, she said.
The shift of muon neutrinos to electron neutrinos detected in the new experiment is a new type of neutron oscillation that opens the way for new studies of a matter-antimatter symmetry called charge-parity, or CP violation, said Marino. “This CP violation phenomenon has not yet been observed in a neutrino, but may be the reason that our universe today is made up mostly of matter and not antimatter,” she said.
Scientists believe matter and antimatter were present in nearly equal proportions at the onset of the Big Bang. Since matter and antimatter particles cancel each other out, it has been proposed that there must have been CP violation in the early universe that produced slightly more matter than antimatter, which accounts for all the stars, galaxies, planets and life present today.
The T2K project is a collaboration of roughly 500 scientists from 12 nations. Other participating U.S. institutions include Boston University, Brookhaven National Laboratory, the University of California-Irvine, Colorado State University, Duke University, Louisiana State University, Stony Brook University, the University of Pittsburgh, the University of Rochester and the University of Washington. The United States contingent is funded by the U.S. Department of Energy.
The CU-Boulder group includes Marino, physics Associate Professor Eric D. Zimmerman, postdoctoral researchers Stephen Coleman and Robert Johnson, graduate students Andrew Missert and Tianlu Yuan, and former undergraduates Christopher Vanek, Bryan Kaufman, Eric Hansen, Zhon Butcher and Joshua Spitz.
The CU-Boulder team designed and built one of three magnetic horns used to generate neutrino beams. The horns are large aluminum conductors that use very high electrical currents to produce a magnetic field. The magnetic field focuses on short-lived neutrino-producing particles called pions and kaons, enhancing the intensity of the neutrino beam, said Zimmerman.
The CU-Boulder researchers also developed a device to monitor the position of the proton beam that creates the neutrinos. In addition, they contributed to the installation and operation of a T2K detector at the J-PARC site 60 miles northeast of Tokyo that measures the neutrinos right after they are produced, Marino said.
Zimmerman said more data will be required to confirm the new results. The J-PARC accelerator is being repaired following damage from the earthquake that hit Japan on March 11. The accelerator and experiment are expected to be operational again by the end of the year, said Zimmerman.