A new map reveals radio waves from tens of thousands of galaxies

The picture lifts a veil on the history of star formation in the universe

Southern Hemisphere

In this image from a small patch of sky in the Southern Hemisphere, nearly every point of light is radio emission from a galaxy that’s churning out stars. The handful of hourglass-shaped blobs are fountains of gas spewing away from supermassive black holes in the centers of some galaxies.


Never-before-seen radio waves from tens of thousands of galaxies have a secret to share: The height of star formation in the cosmos may have been more prolific than previously imagined.

Radio telescopes are good probes of star formation. But until now, they haven’t been sensitive enough to see radio waves coming from the vast majority of galaxies that produced stars during the peak of star production, an epoch roughly 10 billion years ago known as cosmic noon (SN: 6/20/14).

Now, a new image from the MeerKAT observatory in South Africa has lifted the radio veil on those unsung galaxies. In that image, more than 17,000 pinpoints of radio energy — nearly every one a star-forming galaxy — fill a patch of sky that, as seen from Earth, could be covered by about five full moons.

Using about 10,000 well-studied nearby galaxies as a template, James Condon and his colleagues calculated how luminous and how far away all those points of light must be. To match the observations, the radio waves must come from star-forming galaxies at cosmic noon churning out stars at about 10 times the rate of modern galaxies, says Condon, an astrophysicist at the National Radio Astronomy Observatory in Charlottesville, Va.

What’s more, he says, there are a little less than twice as many of these sources as expected, suggesting that star formation was much higher around cosmic noon than predicted by calculations based on infrared, optical and ultraviolet data. These preliminary results appear December 15 at arXiv.org. 

Christopher Crockett is an Associate News Editor. He was formerly the astronomy writer from 2014 to 2017, and he has a Ph.D. in astronomy from the University of California, Los Angeles.

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