article image

Thousands of unseen, faraway galaxies in Hubble's first Frontier Field

Jenny Winder, News Writer
Jan 9, 2014, 8:00 UTC

Sen—The Hubble Space Telescope has produced an unprecedented view of the Universe. The longest and deepest exposure obtained to date of a cluster of galaxies shows some of the faintest and youngest galaxies ever detected.

The Hubble exposure comes from an ambitious collaborative project called The Frontier Fields. It will be combined with images from Spitzer and NASA's Chandra X-ray Observatory. Assembly of all this multispectral information is expected to provide new insights into the origin and evolution of galaxies and their accompanying black holes.

The target is the massive cluster Abell 2744, which contains several hundred galaxies as they looked 3.5 billion years ago. The immense gravity in this foreground cluster is being used as a "gravitational lens," which warps space to brighten and magnify images of far-more-distant background galaxies as they looked over 12 billion years ago, not long after the big bang.

Hubble Frontier Field Abell 2744. Image credit NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI)

"The Frontier Fields is an experiment; can we use Hubble's exquisite image quality and Einstein's theory of General Relativity to search for the first galaxies?" said Space Telescope Science Institute Director Matt Mountain. "With the other Great Observatories, we are undertaking an ambitious joint program to use galaxy clusters to explore the first billion years of the universe's history."

The Hubble exposure reveals nearly 3,000 of these background galaxies, interleaved with images of hundreds of foreground galaxies in the cluster. The background galaxies are magnified to appear up to 10 to 20 times larger than they would normally appear. What's more, the faintest of these highly magnified objects have intrinsic brightnesses roughly 10 to 20 times fainter than any galaxies ever previously observed.

Though the foreground cluster Abell 2744 has been intensively studied, the Frontier Fields exposure reveals new details of the cluster population. Hubble sees dwarf galaxies in the cluster as small as 1/1,000th the mass of the Milky Way as well as the extended light from several monster central cluster galaxies that are as much as 100 times more massive than our galaxy.

These new deep images will also help astronomers map out the dark matter, that makes up the bulk of the mass of the cluster, with unprecedented detail, by charting its distorting effects on background light.

As the Abell cluster was being photographed with Hubble's Wide Field Camera 3, the telescope's Advanced Camera for Surveys was trained on a nearby parallel field that is 6 arc minutes away from the cluster. In this field, Hubble resolves roughly 10,000 galaxies seen in visible light, most of which are randomly scattered galaxies. The blue galaxies are distant star-forming galaxies seen from up to 8 billion years ago; the handful of larger, red galaxies are in the outskirts of the Abell 2744 cluster.

Hubble will view these two Frontier Fields in May 2014, but Hubble's visible-light and infrared camera will switch targets. This will allow for both fields to be observed over a full range from ultraviolet light to near-infrared.