The Universe’s Baby Boom
A new telescope will tell us how the first stars and galaxies were born.
- By Bruce Lieberman
- Air & Space magazine, August 2013
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How far back in time ALMA will be able to look will be limited by when dusty galaxies existed in cosmic history. It’s the dust emissions that ALMA detects, and Hubble observations suggest that as we look closer to the beginning of the universe—going from when re-ionization was complete back to the ignition of those first stars—the universe gets progressively freer of dust.
“Now, ALMA may tell us a different story, and that would be very interesting,” says Caltech astronomer Richard Ellis. “I think there’s a lot of hype about ALMA that is unproven yet, but it’s realistic to be optimistic. We know so little about early galaxies that the basic argument is ‘Let’s go and have a look and see what we see.’ ”
One of the next tests for ALMA will be to see if it can detect smaller, dimmer galaxies, which are predicted to be far more common within the first billion years of the Big Bang, rather than the monster starburst galaxies discovered by Vieira and others last year. “Much of the re-ionization is done by feeble little things, and so we would dearly like to get details of their properties,” Ellis says.
Ellis is on a team led by University of Edinburgh astronomer James Dunlop that will use ALMA to image 100 galaxies within the Hubble Ultra Deep Field. Last January at the annual meeting of the American Astronomical Society in Long Beach, California, Ellis’ team announced that, within Hubble’s infrared data, they had tentatively found a handful of galaxies that existed when the universe was just 570 million years old, and one that existed at just 370 million years, making it the most distant and earliest object ever discovered.
Using ALMA, Ellis’ team will study these galaxies for dust, an indicator of how early heavy elements began appearing. “This will capture most of the stuff that Hubble cannot see,” says Dunlop. “If you want to make a complete census of cosmic star formation history, you’ve got to measure the un-obscured stuff that you see with Hubble, and the obscured stuff.”
For seeing the obscured stuff, nothing beats ALMA.
Bruce Lieberman is a freelance science writer in Carlsbad, California.