Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

In Deep Galaxy Surveys, Astronomers Get a Boost from Gravity

14.01.2011
Astronomers who survey galaxies in the distant universe are getting some unexpected help from gravity, according to a new study.

In a presentation at the American Astronomical Society meeting this week and a related paper in the current issue of the journal Nature, researchers say that as many as 20 percent of the most distant galaxies currently detected appear brighter than they actually are, because of an effect called "strong gravitational lensing."

The discovery could change astronomers' notions of how galaxies formed in the early universe. It will also be important in the planning for how to effectively use NASA's planned James Webb Space Telescope (JWST) for hunting very distant galaxies.

Principal investigator Stuart Wyithe of the University of Melbourne calculated the lensing effect at various distances. Wyithe and Haojing Yan, postdoctoral fellow at the Center for Cosmology and Astro-Particle Physics at Ohio State University, collaborated with Rogier Windhorst at Arizona State University and Shude Mao of the University of Manchester and the Chinese Academy of Sciences.

Yan reports that astronomers have long known about strong gravitational lensing, but thought it only happens rarely, and wouldn't have any real impact on galaxy surveys.

"On one hand, lensing is good for us in that it enables us to detect galaxies that would otherwise be invisible, but on the other hand we will need to correct our surveys to obtain accurate tallies," Yan says.

From our view on Earth, if a faraway galaxy and a nearby galaxy line up on the sky, the gravity of the nearby galaxy bends the light from the faraway galaxy, as if the nearer galaxy were a magnifying glass, or lens.

Einstein predicted decades ago that gravity could bend light, and astronomers have since proven him right. In fact, modern astronomers exploit the effect to find distant objects that would otherwise be invisible, such as planets orbiting other stars.

And in this case, a statistical analysis revealed that gravitational lensing is brightening faraway galaxies that would otherwise be too faint to see.

Now that astronomers are aware of the effect, they can use it to their advantage.

"We just need to be aware that we are looking through 'lenses,'" Yan said. "Take a real magnifying glass as an example: through the lens we can see more details of an object - which is a good thing - but you should be aware that all those details are not actually the sizes that you see, because you're looking through a magnifying lens. The same is true when we're looking at galaxies."

"We predict that many galaxies in the most remote universe will only ever be visible to us because they are magnified in this way," he adds.

Clues From Hubble

Yan is part of an international team of astronomers who are using NASA's Hubble Space Telescope to probe the distant universe. They analyze images from the Hubble Ultra Deep Field (HUDF) survey, a collection of the furthest images of the universe ever taken.

The survey looks back in time 13 billion years, to when the universe was less than one billion years old. Astronomers want to know how many galaxies were

bright or faint when the universe was still in that infant stage. So any magnification of those galaxies will interfere with astronomers' ability to judge.

Even through the eyes of Hubble, these faraway galaxies look very small, so it's hard to tell which ones have been magnified. Yet tallies from the HUDF survey are critical to scientists' understanding of how galaxies formed and evolved.

"Although we do not yet have an instrument to directly detect a lensing 'signature' to unambiguously support our prediction, we now have some indirect, tentative evidence that the number of lensed galaxies could be high as we look into the early universe," Yan says. "The apparent association of very distant galaxies to galaxies in the foreground is the key."

Sometimes, the gravitational lensing distorts a galaxy's appearance, or alters its brightness. Other times, the lens splits the light from the faraway galaxy so that two or more galaxies will form around the lens, when there is really only one.

In fact, Yan and his colleagues began this work in order to understand why so many of the faraway galaxies they observed in HUDF survey images appear to be located near the line of sight to galaxies in the foreground.

Through a statistical analysis, they determined that strong gravitational lensing is the most likely explanation.

Yan stressed that the 20-percent estimate is an initial one, and could change in the future.

"We want to make it clear that the size of the effect depends on a number of uncertain factors. If, for example, very distant galaxies are much fainter than their nearby counterparts but much more numerous, the majority of such distant galaxies that we will detect in the foreseeable future could be lensed ones," he says.

According to Yan and his colleagues, the impact of gravitational lensing on galaxy surveys will be even higher in future studies.

Exactly how much is an open question, and Yan says that only the James Webb Space Telescope, set for launch later this decade, could provide a decisive answer.

Yan's discovery suggests that when astronomers use JWST to hunt for faraway galaxies, they should search close to foreground galaxies.

"At Hubble's resolution one literally can no longer see the whole 'forest for the trees' at these extreme distances. Only the James Webb Space Telescope will have the exquisite resolution and sensitivity to disentangle these very distant objects from the foreground lensing galaxies,'' adds Windhorst.

"This also means that JWST needs to have a very good resolution, so that the galaxies won't just blend together," says Mao.

Funding for this work came from the Australian Research Council, the Space Telescope Science Institute, a NASA-JWST Interdisciplinary Scientist grant, and Yan's fellowship at the Center for Cosmology and Astro-Particle Physics at Ohio State.

A graphic created by the Space Telescope Science Institute is available to members of the news media; contact Pam Frost Gorder. The graphic is also available at:

http://hubblesite.org/news/2011/04
http://www.nasa.gov/aas
http://www.asu.edu/clas/hst/www/jwst/HUDFjavatool/index.html
http://researchnews.osu.edu/archive/deeplens.htm
http://www.asu.edu/clas/hst/www/nature11/
The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI) conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington, D.C.

Ray Villard | Newswise Science News
Further information:
http://www.stsci.edu

More articles from Physics and Astronomy:

nachricht What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin

nachricht Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Pollen taxi for bacteria

18.07.2018 | Life Sciences

Biological signalling processes in intelligent materials

18.07.2018 | Life Sciences

Study suggests buried Internet infrastructure at risk as sea levels rise

18.07.2018 | Information Technology

VideoLinks
Science & Research
Overview of more VideoLinks >>>