Paris, Feb 19 : Astronomers using the NASA/ESA Hubble Space Telescope have discovered 67 gravitationally lensed galaxies in the distant Universe.
A team of European astronomers led by Jean-Paul Kneib and Cecile Faure analysed the results from Hubble's Advanced Camera for Surveys (ACS).
What the astronomers have done is that they have compiled a large catalogue of 67 new gravitationally lensed galaxy images found around massive elliptical and lenticular-shaped galaxies.
Gravitational lensing occurs when light travelling towards us from a distant galaxy is magnified and distorted as it encounters a massive object between the galaxy and us. These gravitational lenses often allow astronomers to peer much further back into the early Universe than they would normally be able to.
The massive objects that create the lenses are usually huge clusters of massive galaxies.
"We typically see the gravitational lens create a series of bright arcs or spots around a galaxy cluster. What we are observing here is a similar effect but on much smaller scale - happening only around a single but very massive galaxy," said Jean-Paul Kneib.
The lenses come from a recently completed, large set of observations as part of a huge project to survey a single 1.6 square degree field of sky (nine times the area of the full Moon) with several space-based and Earth-based observatories.
From ACS high-resolution images, complemented by the extensive ground-based follow-up observations, astronomers identified these 67 strong gravitationally lensed galaxies.
These were found around very massive galaxies that are usually elliptical or lenticular in shape and often exhibit a paucity of gas and dust without spiral arms or discs.
The strong lensing produced by massive galaxies is much more common than the usual giant "arc" gravitationally lensed galaxies that Hubble has previously observed; but they are generally more difficult to find as they extend over a smaller area and have a wide variety of shapes.
"With this sample of gravitational systems identified by the human eye, we now plan use the sample of lenses to train robot software to find more of these lenses across the entire Hubble image archive, and we may find even more strong lensing systems in the COSMOS field," said Jean-Paul Kneib.
The study of these gravitational lenses will give astronomers a first-rate opportunity to probe the dark matter distribution around galactic lenses.
Once astronomers find even larger numbers of these smaller, stronger lenses they can be used to create a census of galaxy masses in the Universe to test the predictions of cosmological models.