Unusual cosmic lens discovered
By ANISaturday, July 17, 2010
WASHINGTON - Astronomers have discovered the first known case of a distant galaxy being magnified by a quasar acting as a gravitational lens.
The discovery, by researchers at the California Institute of Technology (Caltech) and Ecole Polytechnique Fidirale de Lausanne (EPFL) in Switzerland, appears in the journal Astronomy and Astrophysics.
Quasars - extraordinary luminous objects in the distant universe are thought to be powered by supermassive black holes in the cores of galaxies. A single quasar could be a thousand times brighter than an entire galaxy of a hundred billion stars, which makes studies of their host galaxies exceedingly difficult. The significance of the discovery, the researchers claim, is that it provides a novel way to understand these host galaxies.
“It is a bit like staring into bright car headlights and trying to discern the color of their rims,” said Fridiric Courbin of EPFL, the lead author on the paper. Using gravitational lensing, “we now can measure the masses of these quasar host galaxies and overcome this difficulty,” he said.
To find the cosmic lens, the astronomers searched a large database of quasar spectra obtained by the Sloan Digital Sky Survey (SDSS) to select candidates for “reverse” quasar-galaxy gravitational lensing. Follow-up observations of the best candidate - quasar SDSS J0013+1523, located about 1.6 billion light years away - using the W. M. Keck Observatory’s 10-meter telescope, confirmed that the quasar was indeed magnifying a distant galaxy, located about 7.5 billion light years away.
“We were delighted to see that this idea actually works. This discovery demonstrates the continued utility of gravitational lensing as an astrophysical tool,” said Georges Meylan, a professor of physics and leader of the EPFL team.
“Quasars are valuable probes of galaxy formation and evolution,” said Professor of Astronomy S. George Djorgovski, leader of the Caltech team.
“Discoveries of more such systems will help us understand better the relationship between quasars and the galaxies which contain them, and their coevolution,” he added. (ANI)
