What little do we know dark matter They come from calculations based on the glow of surrounding galaxies. However, the farther away we looked, the fainter the starlight became, making it difficult to see the subtle influence of these more mysterious forces.
A collaboration of astronomers from Japan and the United States has found a different way to illuminate distant darkness, by studying the way mysterious lumps of dark matter distort the background glare of the universe.
Like images dropped from a moving car, the entire history of our universe is smeared across the vastness of space. To see a succession of significant moments, all we need to do is keep looking down the highway.
Unfortunately, the soaring expansion of everything wasn’t kind to those old shots, stretching their panels of starlight until they’re depleted of energy, seeming to us little more than glowing embers.
It’s a shame we can’t see them as they are. If those early galaxies are anything like the ones we see later in the universe’s timeline, their structure must have been influenced by pockets of gravity created by…well, we have no idea.
It is called dark matter only because it does not emit any information that tells us anything about its nature. Probably a particle-like mass with few properties, not unlike a neutrino. There is an external chance that it is a reflection of something we misunderstood about the formation of space and time.
In short, we still do not have a concrete theory as to where this phenomenon fits into current physics. So getting an accurate measure of what very ancient dark matter halos looked like will at least tell us if they have changed over time.
We cannot estimate its total mass – invisible and incandescent – by measuring its faint light. But it is possible to use the way their collective mass distorts starlight passing through the space around them.
This lensing technology works well enough for large groups of galaxies seen 8 to 10 billion years in the past. The more we want to see, the less background stellar radiation we want to analyze for distortions.
According to Nagoya University astrophysicist Hironao Miyatake and colleagues, there is another light source we can use, called cosmic microwave background (CMB).
Think of the CMB as the oldest image of a newborn universe. The light emitted resonates when the universe was about 300,000 years old, and now it penetrates into space in the form of weak radiation.
Scientists use subtle patterns in this background buzz to test all kinds of hypotheses in the early critical stages of the universe’s evolution. His use was first to estimate the average mass of distant galaxies and the distribution of their surrounding dark matter halos.
“It was a crazy idea. Nobody realized we could do that,” Says Masami Oshi, an astrophysicist from the University of Tokyo.
“But after I gave a talk about a large, distant galaxy sample, Hironao came to me and said that it might be possible to look at the dark matter around these galaxies using the CMB.”
Hironao and his colleagues focused on a special group of distant star-forming objects called Lyman Break Galaxies.
Using a sample of nearly 1.5 million of these objects collected by the Hyper Suprime-Cam Subaru strategic reconnaissance, they analyzed microwave radiation patterns as seen by the European Space Agency’s Planck satellite.
The results provided the researchers with a typical halo mass for galaxies closer to 12 billion years in the past, an era somewhat different from the one we see closer to home today.
According to standard cosmological theory, the composition of those early galaxies was largely determined by fluctuations in space that amplify the clump of matter. Interestingly, these new discoveries of early galactic masses reflect less clumping of matter than current preferred models predict.
“Our discovery is still uncertain”, Says Miyatake. “But if true, it suggests that the entire model is flawed as you go back in time.”
Revisiting current models of how fresh elements came together to form the first galaxies could reveal gaps that may also explain the origins of dark matter.
Although the images of the children of the universe have faded, it is clear that they still have a story to tell about how we came to be.
This research was published in physical review messages.