Summary of the Hubble Frontier Fields Initiative

2/4/2014

Summary of the Hubble Frontier Fields Initiative

"The history of astronomy is the history of receding horizons." - Edwin Hubble

The Hubble Frontier Field initiative is a project that primarily uses the Hubble Space Telescope. The telescope observes distant galaxies, magnified through gravitational lensing from galaxy clusters. This Initiative is currently being done to help astronomers look deeper into the universe, to learn more about learn more about dark matter, and to learn about the first galaxies after the Big Bang. Galaxy clusters are large groups of galaxies, held together through non-baryonic (matter not made up of neutrons, protons and electrons, and thus not likely any of the known chemical elements) matter; another name for this mysterious matter is “dark matter.” In Einstein’s theory of relativity states that light passing near a mass of object is bent by the curvature of space. A cluster of Galaxies can act as a lens and bend the light in our direction so Hubble can view it.

 (Top)
A representation of how light bends due to the gravity in Abell 2744, or Pandora's cluster
(Bottom)
A quick video simulating gravitational lensing 

The light is also magnified which allows us to see more distant galaxies making the Frontier Field initiative a step towards understanding the early universe. The HFF initiative allows us to see galaxies that appeared in the first few hundred million years of the universe.The Frontier Fields are selected to be among the strongest lensing clusters on the sky. There are currently a handful of Frontier Field candidates shown here below.

Cluster	z	RA	DEC
Abell 370	0.37	02:39:52.8	-01:34:36
MACSJ0329.6-0211	0.45	03:29:40.3	-02:11:42
MACSJ0416.1-2403	0.42	04:16:08.4	-24:04:21
MACSJ0451.0+0006	0.429	04:51:54.6	+00:06:17
MACSJ0717.5+3745	0.545	07:17:35.6	+37:44:44
MACSJ0744.9+3927	0.686	07:44:52.8	+39:27:24
MACSJ1149.5+2223	0.543	11:49:35.7	+22:23:55
MACSJ1423.8+2404	0.54	14:23:48.3	+24:04:47
Abell 2744	0.308	00:14:23.4	-30:23:26
MACSJ0257-2325	0.505	02:57:08.8	-23:26:03
MACSJ0520.7-1328	0.340	05:20:42.0	-13:28:48

These candidates were selected primarily based upon their lensing properties. Such properties are as of the following.

•         The clusters are known to be massive and highly efficient lenses
•          The clusters have several sets of known multiple image systems confirmed with spectroscopic red shifts
•          Most of the clusters have high-quality magnification maps based on data in hand.

       

Frontier Field Abell 2744 (Pandora's Cluster)

       A perfect example of gravitational lensing is the long-exposure image of massive galaxy cluster Abell 2744 (Pandora's Cluster). This cluster warps space to brighten and magnify images of far-more-distant background galaxies as they looked over 12 billion years ago. The Hubble Image above reveals nearly 3,000 of these background galaxies interleaved with images of hundreds of foreground galaxies in the cluster. Though the Pandora Cluster 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. On the other side, there has been galaxies discovered that are 100 times massive as the Milky Way. Images like the one above can help astronomers map out the dark matter in the cluster with detail, by charting its distorting effects on background light. Dark matter makes up the bulk of the mass of the cluster. 

      

The Frontier Field initiative has many goals. The Frontier Field is undertaking a revolutionary deep field observing program to peer deeper into the Universe than ever before, combined with the natural lensing of the galaxy clusters. The Hubble Space Telescope will produce the deepest observations of clusters and their lensed galaxies ever obtained. The initiative will help astronomers learn more of the distant galaxies that are magnified through the natural lens of clusters. Images taken by the telescope will reveal distant galaxy populations ~10-100 times fainter than any previously observed and improve the statistical understanding of galaxies during the epoch of reionization, and provide new measurements of dark matter within the galaxy clusters.

The Frontier Field Initiative challenges and answers many scientific questions about the early universe. Such questions were as the following.

• How far back into the universe can we look?
• What is the faintest- and possibly most distant- galaxy we can see not with the Hubble Space Telescope?
• What is the distribution of Dark Matter in the known universe?
• What did the first galaxies look like?       

As I read through and took notes from many websites containing vast data and information regarding the Frontier Fields, I had a few questions. What is reionization? What is its importance to the Frontier Fields? Another question was that why does the Hubble Space Telescope have to stare at a blank spot for hours? Do all galaxy clusters have gravitational lensing? If not, what makes them different from the galaxies that do have gravitational lensing? I believe these questions will help me continue on with research and help me understand the "hot topic" in Astronomy known as gravitational lensing.

- Ben Schiher

Resources:

• http://hubblesite.org/newscenter/archive/releases/2014/01/
• http://www.stsci.edu/~postman/CLASH/For_Astronomers.html
• http://www.stsci.edu/hst/campaigns/frontier-fields/
• http://hubblesite.org/newscenter/archive/releases/2012/36/
• frontierfields.org

Thanks to,

Dr. John Moustakas, Siena College