Hubble finds strong contender for galaxy distance record

Detailed images from Hubble’s Near Infrared Camera and Multi-Object Spectrometer (NICMOS) reveal an infant galaxy, dubbed A1689-zD1, undergoing a firestorm of star birth as it comes out of the dark ages, a time shortly after the Big Bang, but before the first stars completed the reheating of the cold, dark Universe. Images from NASA’s Spitzer Space Telescope’s Infrared Array Camera provided strong additional evidence that it was a young star-forming galaxy in the dark ages.

“We certainly were surprised to find such a bright young galaxy 13 billion years in the past”, said astronomer Garth Illingworth of the University of California, Santa Cruz, USA and a member of the research team. “This is the most detailed look to date at an object so far back in time.”

According to the authors, the measurements are “highly reliable”. “This object is the strongest candidate for the most distant galaxy so far”, states team member Piero Rosati from ESO, Germany.

“The Hubble images yield insight into the galaxy’s structure that we cannot get with any other telescope,” added astronomer Rychard Bouwens of the University of California, Santa Cruz, one of the co-discoverers of this galaxy.

The new images should offer insights into the formative years of galaxy birth and evolution and yield information on the types of objects that may have contributed to ending the dark ages. During its lifetime the Hubble telescope has peered ever farther back in time, viewing galaxies at successively younger stages of evolution. These snapshots have helped astronomers create a scrapbook of galaxies from infancy to adulthood. The new Hubble and Spitzer images of A1689-zD1 show a time when galaxies were in their infancy.

Current theory holds that the dark ages began about 400,000 years after the Big Bang, as matter in the expanding Universe cooled and formed clouds of cold hydrogen. These cold clouds pervaded the Universe like a thick fog. At some point during this era, stars and galaxies started to form. Their collective light heated and cleared the fog of cold hydrogen, and ended the dark ages about a billion years after the Big Bang.

“This galaxy presumably is one of the many galaxies that helped end the dark ages”, said astronomer Larry Bradley of Johns Hopkins University in Baltimore, USA, and leader of the study. “Astronomers are fairly certain that high-energy objects such as quasars did not provide enough energy to end the dark ages of the Universe. But many young star-forming galaxies may have produced enough energy to end it.”

The galaxy is so far away it did not appear in visible light images taken with Hubble’s Advanced Camera for Surveys, because its light is stretched to infrared wavelengths by the Universe’s expansion. It took Hubble’s NICMOS, Spitzer and a trick of nature called gravitational lensing to see the faraway galaxy.

The astronomers used a relatively nearby massive cluster of galaxies known as Abell 1689, roughly 2.2 billion light-years away, to magnify the light from the more distant galaxy directly behind it. This natural telescope is a gravitational lens. Abell 1689 is one of the most spectacular gravitational telescopes known and its gravitational properties are very well known.

Though the diffuse light of the faraway object is nearly impossible to see, gravitational lensing has increased its brightness by nearly 10 times, making it bright enough for Hubble and Spitzer to detect. A telltale sign of the lensing is the smearing of the images of galaxies behind Abell 1689 into arcs by the gravitational warping of space by the intervening galaxy cluster. Piero Rosati says: “This galaxy lies near the region where the galaxy cluster produces the highest magnification – which was essential to bring this galaxy within reach of Hubble and Spitzer.”

Spitzer’s images show that the galaxy’s mass is typical of galaxies in the early Universe. Its mass is equivalent to several billions of stars like our Sun, or just a tiny fraction of the mass of the Milky Way.

“This observation confirms previous Hubble studies that star birth happens in very tiny regions compared with the size of the final galaxy”, Illingworth said.

The faraway galaxy also is an ideal target for Hubble’s successor, the James Webb Space Telescope (JWST), scheduled to launch in 2013. Even with the increased magnification from the gravitational lens, Hubble’s sharp “eye” can only see knots of the brightest, heftiest stars in the galaxy. The telescope cannot pinpoint fainter, lower-mass stars, individual stars, or the material surrounding the star-birth region. To see those things, astronomers will need the infrared capabilities of JWST currently being developed by NASA, ESA and CSA in a major international collaboration. The planned infrared observatory will have a mirror about seven times the area of Hubble’s primary mirror and will collect more light from faint galaxies. JWST also will be able to view even more remote galaxies whose light has been stretched deep into infrared wavelengths that are out of the reach of NICMOS.

“This galaxy will certainly be one of the first objects that will be observed by JWST”, said team member Holland Ford of Johns Hopkins University. “This galaxy is so bright that JWST will see its detailed structure. This object is a pathfinder for JWST for deciphering what is happening in young galaxies.”

The astronomers noted that the faraway galaxy also would be an ideal target for the ESO/NRAO/NAOJ Atacama Large Millimeter Array (ALMA), which, when completed in 2012, will be the most powerful radio telescope in the world. “ALMA and JWST working together would be an ideal combination to really understand this galaxy”, Illingworth said, noting that: “JWST’s images and ALMA’s measurement of the gas motions will provide revolutionary insights into the very youngest galaxies.”

The astronomers will conduct follow-up observations with infrared spectroscopy to confirm the galaxy’s distance using ESO’s VLT and the Keck telescope atop Mauna Kea in Hawaii.

The results will be published in the Astrophysical Journal.

Source: ESA/Hubble Information Centre

Related stories:

Stars stop forming when big galaxies collide
Astronomers studying new images of a nearby galaxy cluster have found evidence that high-speed collisions between large elliptical galaxies may prevent new stars from forming, according to a paper to be published in a November 2008 issue of The Astrophysical Journal Letters.
When It Comes to Galaxies, Diversity Is Everywhere
(PhysOrg.com) -- There's an old saying in astronomy: "Galaxies are like people. They're only normal until you get to know them." That view is supported by a group of astronomers after using NASA's Hubble Space Telescope to study a large number of galaxies in our cosmic backyard.
Galaxy Zoo -- an Internet superstar
Since Galaxy Zoo's launch in July 2007, some 150,000 members of the public, inspired by the opportunity to be the first to see and classify a galaxy, have helped professional astronomers via this on-line mass-participation project to carry out real scientific research.
How Do Galaxies Grow?
How do galaxies form? The most widely accepted answer to this fundamental question is the model of 'hierarchical formation', a step-wise process in which small galaxies merge to build larger ones. One can think of the galaxies forming in a similar way to how streams merge to form rivers, and how these rivers, in turn, merge to form an even larger river. This theoretical model predicts that massive galaxies grow through many merging events in their lifetime. But when did their cosmological growth spurts finish? When did the most massive galaxies get most of their mass?
XMM-Newton's massive discovery
(PhysOrg.com) -- ESA's orbiting X-ray observatory XMM-Newton has discovered the most massive cluster of galaxies seen in the distant Universe until now. The galaxy cluster is so big that there can only be a handful of them at that distance, making this a rare catch indeed. The discovery confirms the existence of dark energy.
'Cosmic ghost' discovered by volunteer astronomer
When Yale astrophysicist Kevin Schawinski and his colleagues at Oxford University enlisted public support in cataloguing galaxies, they never envisioned the strange object Hanny van Arkel found in archived images of the night sky.
Caltech astronomers describe the bar scene at the beginning of the universe
Bars abound in spiral galaxies today, but this was not always the case. A group of 16 astronomers, led by Kartik Sheth of NASA's Spitzer Science Center at the California Institute of Technology, has found that bars tripled in number over the past seven billion years, indicating that spiral galaxies evolve in shape.
Rare 'Star-Making Machine' Found in Distant Universe
Astronomers have uncovered an extreme stellar machine -- a galaxy in the very remote universe pumping out stars at a surprising rate of up to 4,000 per year. In comparison, our own Milky Way galaxy turns out an average of just 10 stars per year.

News discussion:

Space & Earth science news