Johns Hopkins leads study finding first observed evidence of galactic-wind phenomenon
Research led by Johns Hopkins University scientists has found new persuasive evidence that could help solve a longstanding mystery in astrophysics: Why did the pace of star formation in the universe slow down some 11 billion years ago?
A paper published in the Monthly Notices of the Royal Astronomical Society finds evidence supporting the argument that the answer was energy feedback from quasars within the galaxies where stars are born. That is, intense radiation and galaxy-scale winds emitted by the quasars - the most luminous objects in the universe - heats up clouds of dust and gas. The heat prevents that material from cooling and forming more dense clouds, and eventually stars.
"I would argue that this is the first convincing observational evidence of the presence of quasar feedback when the universe was only a quarter of its present age, when the cosmic star formation was most vigorous," said Tobias Marriage, an assistant professor in the university's Henry A. Rowland Department of Physics and Astronomy. While the findings appearing in the journal published by the Oxford University Press are not conclusive, Marriage said, the evidence is very compelling and has scientists excited.
"It's like finding a smoking gun with fingerprints near the body, but not finding the bullet to match the gun," Marriage said.
Specifically, investigators looked at information on 17,468 galaxies and found a tracer of energy known as the Sunyaev-Zel'dovich Effect. The phenomenon, named for two Russian physicists who predicted it nearly 50 years ago, appears when high-energy electrons disturb the Cosmic Microwave Background. The CMB is a pervasive sea of microwave radiation, a remnant from the superheated birth of the universe some 13.7 billion years ago.
Devin Crichton, a Johns Hopkins graduate student and the paper's lead author, said the thermal energy levels were analyzed to see if they rise above predictions for what it would take to stop star formation. A large number of galaxies were studied to give the study statistical heft, he said.
"For feedback to turn off star formation, it must be occurring broadly," said Crichton, one of five Johns Hopkins scientists who led the work conducted by a total of 23 investigators from 18 institutions. Most of the scientists are members of the Atacama Cosmology Telescope collaboration, named for one of the three instruments used in the study.
To take the faint temperature measurements that would show the Sunyaev-Zel'dovich Effect, the scientists used information gathered by two ground-based telescopes and one receiver mounted on a space observatory. Using several instruments with different strengths in search of the SZ Effect is relatively new, Marriage said.
"It's a pretty wild sort of thermometer," he said.
Information gathered in the Sloan Digital Sky Survey by an optical telescope at the Apache Point Observatory in New Mexico was used to find the quasars. Thermal energy and evidence of the SZ Effect were found using information from the Atacama Cosmology Telescope, an instrument designed to study the CMB that stands in the Atacama Desert in northern Chile. To focus on the dust, investigators used data from the SPIRE, or Spectral and Photometric Imaging Receiver, on the Herschel Space Observatory.
Galaxies reached their busiest star-making pace about 11 billion years ago, then slowed down. A team of astronomers more than three years ago estimated that the pace of star formation is one-thirtieth as fast as when it peaked. Scientists have puzzled for years over the question of what happened. The chief suspect has been the feedback process, Marriage said.
Nadia L. Zakamska, an assistant professor in the Department of Physics and Astronomy at Johns Hopkins and one of the report's co-authors, said it is only in the last few years that evidence of this phenomenon from direct observation has been compiled. The SZ Effect, she said, is a novel approach to the subject, making clearer the full effect of galactic wind on the surrounding galaxy.
"Unlike all other methods that are probing small clumps within the wind, the Sunyaev-Zeldovich Effect is sensitive to the bulk of the wind, the extremely hot plasma that's filling the volume of the wind and is completely undetectable using any other technique," she said.
The research was supported by the National Science Foundation, awards AST-0408698 and AST-0965625, PHY-0855887 and PHY-1214379. Funding also provided by Princeton University, the University of Pennsylvania and a Canada Foundation for Innovation award.
Arthur Hirsch | EurekAlert!
Prediction: More gas-giants will be found orbiting Sun-like stars
22.02.2017 | Carnegie Institution for Science
NASA's fermi finds possible dark matter ties in andromeda galaxy
22.02.2017 | NASA/Goddard Space Flight Center
Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...
The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.
The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...
Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...
Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".
Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...
13.02.2017 | Event News
10.02.2017 | Event News
09.02.2017 | Event News
22.02.2017 | Power and Electrical Engineering
22.02.2017 | Life Sciences
22.02.2017 | Physics and Astronomy