The finding is the first age-confirmation of a so-called dropout galaxy at that distant time and pinpoints when an era called the reionization epoch likely began. The research will be published in a December issue of the Astrophysical Journal.
With recent technological advancements, such as the Wide-Field Camera 3 on the Hubble Space Telescope, there has been an explosion of research of the reionization period, the farthest back in time that astronomers can observe. The Big Bang, 13.7 billion years ago, created a hot, murky universe. Some 400,000 years later, temperatures cooled, electrons and protons joined to form neutral hydrogen, and the murk cleared.
Some time before 1 billion years after the Big Bang, neutral hydrogen began to form stars in the first galaxies, which radiated energy and changed the hydrogen back to being ionized. Although not the thick plasma soup of the earlier period just after the Big Bang, this star formation started the reionization epoch. Astronomers know that this era ended about 1 billion years after the Big Bang, but when it began has eluded them and intrigued researchers like lead author Masami Ouchi of the Carnegie Observatories.
The U.S. and Japanese team led by Ouchi used a technique for finding these extremely distant galaxies. "We look for 'dropout' galaxies," explained Ouchi. "We use progressively redder filters that reveal increasing wavelengths of light and watch which galaxies disappear from or 'dropout' of images made using those filters. Older, more distant galaxies 'dropout' of progressively redder filters and the specific wavelengths can tell us the galaxies' distance and age. What makes this study different is that we surveyed an area that is over 100 times larger than previous ones and, as a result, had a larger sample of early galaxies (22) than past surveys. Plus, we were able to confirm one galaxy's age," he continued. "Since all the galaxies were found using the same dropout technique, they are likely to be the same age."
Ouchi's team was able to conduct such a large survey because they used a custom-made, super-red filter and other unique technological advancements in red sensitivity on the wide-field camera of the 8.3-meter Subaru Telescope. They made their observations from 2006 to 2009 in the Subaru Deep Field and Great Observatories Origins Deep Survey North field. They then compared their observations with data gathered in other studies.
Astronomers have wondered whether the universe underwent reionization instantaneously or gradually over time, but more importantly, they have tried to isolate when the universe began reionization. Galaxy density and brightness measurements are key to calculating star-formation rates, which tell a lot about what happened when. The astronomers looked at star-formation rates and the rate at which hydrogen was ionized.
Using data from their study and others, they determined that the star-formation rates were dramatically lower from 800 millions years to about one billion years after the Big Bang, then thereafter. Accordingly, they calculated that the rate of ionization would be very slow during this early time, because of this low star-formation rate.
"We were really surprised that the rate of ionization seems so low, which would constitute a contradiction with the claim of NASA's WMAP satellite. It concluded that reionization started no later than 600 million years after the Big Bang," remarked Ouchi. "We think this riddle might be explained by more efficient ionizing photon production rates in early galaxies. The formation of massive stars may have been much more vigorous then than in today's galaxies. Fewer, massive stars produce more ionizing photons than many smaller stars," he explained.
The work was funded by the Carnegie Institution. The research is based on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan; the Hubble Space Telescope, operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS5-26555; the Spitzer Telescope, managed by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA.
The Carnegie Institution for Science (www.CIW.edu) has been a pioneering force in basic scientific research since 1902. It is a private, nonprofit organization with six research departments throughout the U.S. Carnegie scientists are leaders in plant biology, developmental biology, astronomy, materials science, global ecology, and Earth and planetary science.
Masami Ouchi | EurekAlert!
X-ray photoelectron spectroscopy under real ambient pressure conditions
28.06.2017 | National Institutes of Natural Sciences
New photoacoustic technique detects gases at parts-per-quadrillion level
28.06.2017 | Brown University
An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.
Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...
Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.
Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...
Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.
As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...
Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.
With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...
Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine
Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...
19.06.2017 | Event News
13.06.2017 | Event News
13.06.2017 | Event News
28.06.2017 | Physics and Astronomy
28.06.2017 | Physics and Astronomy
28.06.2017 | Health and Medicine