The first of a set of unprecedented, super-deep views of the universe
from an ambitious collaborative program called The Frontier Fields is
being released today (Jan 7, 2014) at the 223rd meeting of the American Astronomical
Society in Washington, D.C.
The long-exposure image taken with NASA's Hubble Space Telescope is
the deepest-ever picture taken of a cluster of galaxies, and also
contains images of some of the intrinsically faintest and youngest
galaxies ever detected.
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.
"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."
Simultaneous observations of this field are being done with NASA's
two other Great Observatories, the Spitzer Space Telescope and the
Chandra X-ray Observatory. The 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 Hubble exposure reveals nearly 3,000 of these background galaxies
interleaved with images of hundreds of foreground galaxies in the
cluster. The many background galaxies would otherwise be invisible
without the boost from gravitational lensing. Their images not only
appear brighter, but also smeared, stretched, and duplicated across the
field.
Thanks to the gravitational lensing phenomenon, 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.
The Hubble data are immediately being made available to the worldwide
astronomy community where teams of researchers will do a detailed
study of the visual crazy quilt of intermingled background and cluster
galaxies to better understand the stages of galaxy development.
Though the foreground cluster Abell 2744 has been intensively studied
as one of the most massive clusters in the universe, 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. At the other end of the size spectrum, Hubble detects
the extended light from several monster central cluster galaxies that
are as much as 100 times more massive than our Milky Way. Also visible
is faint intra-cluster light from stars inside the cluster that have
been stripped out of galaxies by gravitational interactions. These new
deep images will also help astronomers map out the dark matter in the
cluster with unprecedented detail, by charting its distorting effects
on background light. An unseen form of matter, dark matter makes up the
bulk of the mass of the cluster.
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 again 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 of colors,
from ultraviolet light to near-infrared.
With each new camera installed on Hubble, the space telescope has
been used to make successively deeper, groundbreaking views of the
universe. To get a better assessment of whether doing more deep field
observations was scientifically compelling or urgent, the Space
Telescope Science Institute or STScI in Baltimore, Md., chartered a
"Hubble Deep Field Initiative" working group. The Hubble Frontier Fields
initiative grew out of the working group's high-level discussions at
STScI concerning what important, forward-looking science Hubble should
be doing in upcoming years. Despite several deep field surveys,
astronomers realized that a lot was still to be learned about the far
universe. Such knowledge would help in planning the observing strategy
for the upcoming James Webb Space Telescope.
The astronomers also considered synergies with other observatories,
such as Spitzer, Chandra, and the new Atacama Large
Millimeter/submillimeter Array or ALMA. Over the coming years five more
pairs of fields will be imaged. The next scheduled target is the
massive cluster MACS J0416.1-2403, for which observations are starting
this week.
CONTACT
Ray VillardSpace Telescope Science Institute, Baltimore, Md.
410-338-4514
villard@stsci.edu
