New way to peer at hidden distant galaxies

WASHINGTON - Using the world’s largest space telescope, ESA’s Herschel Space Observatory, a UK-led team has discovered a new way of locating a natural phenomenon that acts like a zoom lens, allowing astronomers to peer at galaxies in the distant and early Universe.

The magnification created by this phenomenon allows astronomers to see galaxies otherwise hidden from us, providing key insights into how galaxies have changed over the history of the cosmos.

Herschel-in operation for over a year in its special orbit 1.5 million km (0.9 million miles) from Earth-looks at far-infrared light, which is emitted not by stars, but by the cool gas and dust from which they form.

David Parker, of the Space Science and Exploration at the UK Space Agency, said, “Once again, the Herschel team have pushed the boundaries and brought us another step closer to understanding the complex birth of stars and galaxies in the early Universe.”

When light from a very distant object passes a galaxy much closer to us, its path can be bent in such a way that the image of the distant galaxy is magnified and distorted. These alignment events are called “gravitational lenses” and many have been discovered over recent decades, mainly at visible and radio wavelengths.

Herschel’s panoramic imaging cameras have allowed astronomers to find examples of these lenses by scanning large areas of the sky in far-infrared and submillimeter light. These results are from the very first data taken as part of the “Herschel-ATLAS” project, the largest imaging survey conducted so far with Herschel, and are published in the prestigious scientific journal Science.

Mattia Negrello, of the Open University and lead researcher of the study, explained, “Our survey of the sky looks for sources of submillimeter light. The big breakthrough is that we have discovered that many of the brightest sources are being magnified by lenses, which means that we no longer have to rely on the rather inefficient methods of finding lenses used at visible and radio wavelengths.”

Negrello and his team investigated five surprisingly bright objects in this small patch of sky. Looking at the positions of these bright objects with optical telescopes on the Earth, they found galaxies that would not normally be bright at the far-infrared wavelengths observed by Herschel.

This led them to suspect that the galaxies seen in visible light might be gravitational lenses magnifying much more distant galaxies seen by Herschel.

To find the true distances to the Herschel sources, Negrello and his team looked for a tell-tale signature of molecular gas. Using radio and submillimeter telescopes on the ground, they showed that this signature implies the galaxies are being seen as they were when the Universe was just 2-4 billion years old — less than a third of its current age.

The galaxies seen by the optical telescopes are much closer, each ideally positioned to create a gravitational lens. Negrello commented that “previous searches for magnified galaxies have targeted clusters of galaxies where the huge mass of the cluster makes gravitational lensing effect unavoidable. Our results show that gravitational lensing is at work in not just a few, but in all of the distant and bright galaxies seen by Herschel.”

The magnification provided by these cosmic zoom lenses allows astronomers to study much fainter galaxies, and in more detail than would otherwise be possible. (ANI)