Nearby bright galaxies have been distorting the view of the earliest galaxies, which are important in understanding what happened to the universe just after the Big Bang, researchers report. Nearby bright galaxies have been distorting the view of the earliest galaxies, which are important in understanding what happened to the universe just after the Big Bang, researchers report.
"Our finding shows images from the earliest galaxies reach us more often via a gravitationally bent path. What you see is not exactly what is really there," astrophysicist Stuart Wyithe from the University of Melbourne
"Our finding shows images from the earliest galaxies reach us more often via a gravitationally bent path. What you see is not exactly what is really there," astrophysicist Stuart Wyithe from the University of Melbourne
Using images from the Hubble Space Telescope, Wyithe and colleagues measured the separation between older, more distant galaxies and brighter foreground galaxies. They compared what they saw to a mathematical model that takes in account gravitational lensing, and concluded that the ancient galaxies were seen to be larger, brighter and more distorted than they actually are.
This effect has likely resulted in inaccurate counts for number density of ancient galaxies as seen by the recent near-IR surveys with the Hubble Space Telescope Wide Field Camera 3, according to the researchers.
But, in a twist, this effect may help astronomers find these distant, hard-to-see galaxies. "The lensing acts as a natural telescope too, so it can also help us find these distant galaxies,” said Wyithe.
Astronomers such as Wyithe study the earliest galaxies - called 'high redshift galaxies' because the light they emit gets shifted to longer wavelengths over time - to understand the source of energy that re-ionised the universe a mere 100, 000 years after the Big Bang.
Most scientists believe that the energy needed to heat the universe's early hydrogen gases to their ionised form came from high-energy photons from stars. However, the numbers of observed early galaxies do not provide enough starlight to account for the injected energy, so scientists continue to search for other fainter, unobservable galaxies.
Astrophysicist Andrew Hopkins from the Australian Astronomical Observatory in New South Wales, who was not involved in the research, said this study is "very exciting" because it ensures astronomers have the most accurate data possible for their search.
"It identifies a clear bias that future surveys of high redshift galaxies will be subject to, and shows what the effect of that bias is. We will actually have a very clear understanding of the true numbers of the highest redshift systems that are out there," he said.
No comments:
Post a Comment