One longstanding mystery in astrophysics is the reason behind that slowed pace of star formation that took place in the universe 11 billon years ago. Now, research by John Hopkins University scientists might have solved this mystery in their new study, which suggests that the answer is energy feedback from quasars within the galaxy in which the stars are born. Although the results are not conclusive, the evidence thus far is very promising.
"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, who participated in the study. "It's like finding a smoking gun with fingerprints near the body, but not finding the bullet to match the gun."
The team examined information on 17,468 galaxies and found signs of energy known as the Sunyaev-Zel'dovich Effect, which occurs when high-energy electrons disturb the Cosmic Microwave Background (CMB), the sea of microwave radiation leftover from the birth of the universe. These thermal energy levels were subsequently measured to determine if they exceeded predictions for the amount it would take to halt star formation.
"For feedback to turn off star formation, it must be occurring broadly," said Devin Crichton, the paper's lead author.
Using information gathered by two ground-based telescopes and one received mounted on a space observatory, the team took faint temperature measurements in order to isolate the Sunyaev-Zel'dovich Effect. They then used information from the Sloan Digital Sky Survey to find quasars and data from the Spectral and Photometric Imaging Receiver (SPIRE) to analyze the dust.
The results showed that in the intense radiation and galactic winds emitted by quasars leads to the heating of dust and gas clouds, which prevents the material from cooling and thus halts the formation of stars. This process might have been what slowed down star formation 11 billion years ago.
Only in the last few years has this phenomenon been observed, and the method of using the Sunyaev-Zeldovich Effect is a novel approach that will likely continue to shed light on the nature of galactic wind and its effects on galaxies.
"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," said Nadia Zakamska, co-author of the study.
The findings were published in the Monthly Notices of the Royal Astronomical Society.
