The Universe May Be Less Crowded Than Scientists Thought

The estimated number of the most distant galaxies has been cut down by new research by 10 to 100 times, says Brian O’Shea, associate professor of physics and astronomy at Michigan State University:

“Our work suggests that there are far fewer faint galaxies than we once previously thought. Earlier estimates placed the number of faint galaxies in the early universe to be hundreds or thousands of times larger than the few bright galaxies that we can actually see with the Hubble Space Telescope. We now think that number could be closer to ten times larger.”

The National Science Foundation’s Blue Waters supercomputer was used to run simulations examining the formation of galaxies in the early universe. O’Shea and his team simulated thousands of galaxies at a time, including the galaxies’ interactions through gravity or radiation.

The simulated galaxies were consistent with those that have been discovered and confirmed.

But the simulations did not show an exponentially growing number of faint galaxies, as has been predicted. The number of those at the lower end of the brightness distribution was flat rather than increasing sharply, O’Shea adds.

When the James Webb Space Telescope finally comes online in late 2018, these simulations will be further tested. The improved technology will enable astronomers to get even finer detailed views of space than the amazing images that the Hubble has produced in recent years.

While the James Webb telescope will improve views of distant galaxies, the telescope has a relatively small field of view. So the observations need to take into account cosmic variance, the statistical variation in the number of galaxies from place to place.

That is what makes these simulations relevant even as improved technology becomes available, O’Shea says.

Brian W. O’Shea, John H. Wise, Hao Xu, and Michael L. Norman
Probing the Ultraviolet Luminosity Function of the Earliest Galaxies with the Renaissance Simulations
ApJ 807 L12. doi:10.1088/2041-8205/807/1/L12

Photo: The much-anticipated James Webb Space Telescope will come online in late 2018. Above, its Engineering Design Unit (EDU) primary mirror segment, coated with gold. (Credit: Drew Noel/NASA via Wikimedia Commons)