In an artist’s conception, heated galactic wind shown in the hazy portion of the picture emanates from the bright quasar at the edge of a black hole, scattering dust and gas. If allowed to cool and condense, that dust and gas would instead begin to form stars. Credit: Johns Hopkins University
Quasars slowed star formation new research shows. It appears 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.
They looked at information on 17,468 galaxies and found a tracer of energy called 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. 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.
“For feedback to turn off star formation, it must be occurring broadly,” said Crichton, a Johns Hopkins scientists who led the work conducted by a total of 23 investigators from 18 institutions. 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.
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 3 years ago estimated that the pace of star formation is 1/30 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.
“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,” Assitant/Prof. Nadia L. Zakamska said. http://releases.jhu.edu/2016/03/22/new-research-shows-quasars-slowed-star-formation/
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