UCI, other scientists find new galaxies through cosmic alignment

UC Irvine astronomers, along with scientists across the globe, are discovering hundreds of new galaxies through brighter galaxies in front of them that deflect their faint light back to the massive Herschel telescope. This effect, identified by Albert Einstein a century ago, is known as cosmic gravitational lensing.

'I was surprised to learn that Herschel is so good at finding these cosmic lenses,' said UCI professor of physics and astronomy Asantha Cooray, lead U.S. author of a paper about the discovery in the Nov. 5 issue of the journal Science. 'We took a map of the sky out there, and it turned out the brightest spots are all gravitationally magnified galaxies. It's a whole new class of galaxies from when the universe was very young.'

The Herschel Space Observatory, a European Space Agency mission with significant NASA contributions, is the largest telescope in space and - to the surprise of astronomers worldwide - has proven adept at locating galactic lenses that reveal magnified galaxies. It's capable of detecting longer-wavelength light than the human eye can - light in the far-infrared portion of the electromagnetic spectrum, which is exactly the type emitted by galaxies lined up behind the ones in the foreground.

'It's just this cosmic alignment,' said UCI associate professor of physics and astronomy Betsy Barton. 'These two galaxies have nothing to do with each other. They're very far apart, and we're very far from both of them. The telescope just happened to be in a place where these two things are aligned.'

When such a lineup occurs, it creates a cosmic magnifying lens, with a massive galaxy or cluster of galaxies bending light from the more distant galaxy into a warped and enlarged image. Sometimes, light from the farther galaxy is so distorted that it appears as a ring - called an Einstein ring because he first predicted the phenomenon. The effect is similar to what happens when you look through the bottom of a glass bottle or into a funhouse mirror.

The new galaxies are in the far reaches of outer space and are being viewed at a time when the universe was only 2 billion to 4 billion years old, less than a third of its current age. Young and bursting with new stars, the galaxies have dust so thick they cannot be seen at all with visible-light telescopes. Herschel can detect the faint warmth of the dust, however, because it glows at far-infrared and submillimetre wavelengths. With these galaxies magnified, astronomers can dig deep into their dusty reaches to learn more about how the universe was created.

'It's a hugely important component in our understanding of when stars formed and what size galaxies were when that happened,' said Barton.

The Science paper - whose lead author is Mattia Negrello of Britain's Open University - reports that five new galaxies were found, but astronomers suspect they've just scratched the surface. 'We can probably pick out hundreds of new lensed galaxies in the Herschel data,' said Paul Goldsmith, the U.S. project scientist for Herschel at NASA's Jet Propulsion Laboratory in Pasadena. Cooray, in fact, estimates that 200 more have been discovered since the article went to press, all awaiting confirmation by ground-based telescopes.

Numerous telescopes around the world helped verify the initial findings, including the National Radio Astronomy Observatory's Green Bank Telescope in West Virginia and three telescopes in Hawaii at the W.M. Keck Observatory, the California Institute of Technology's Submillimetre Observatory and the Smithsonian Astrophysical Observatory's Submillimetre Array.