CFHT News: Elliptical galaxies much younger than previously thought

The standard model for elliptical galaxies formation is challenged by a new result uncovered by an international team of astronomers from the Atlas3D collaboration.

Team members from CNRS, CEA, CFHT (Canada-France-Hawaii-Telescope), and the Observatoire de Lyon published in the scientific journal Monthly Notices of the Royal Astronomical Society the first results from their study on two elliptical galaxies exhibiting features characteristic of a fairly recent merging, suggesting they are five times younger than commonly thought.

The common belief on the mass assembly history of massive elliptical galaxies based on their stellar population leads to an age between 7 and 10 billion years old. A different story is shaping up based on ultra-deep images of two galaxies observed with the MegaCam camera mounted on the Canada-France-Hawaii Telescope (CFHT, CNRC/CNRS/University of Hawaii).

Astronomers from CNRS, CEA, CFHT, and the Observatoire de Lyon, all members of the Atlas3D international collaboration, established that the formation of the two studied elliptical galaxies (NGC 680 & NGC 5557) originated from a merger of two giant spiral galaxies that took place only 1 to 3 billions years ago.

Such age estimate is based on the presence of ultra faint filaments in the distant outskirts of the galaxies. These features called tidal streams in the astronomers parlance are typical residuals from a galaxy merger.

(Click here for a description from the Atlas of Peculiar Galaxies)

They are known not to survive in this shape and brightness for more than a few billion years, hence the new age estimate of the resulting elliptical galaxies. These structures were detected for the first time thanks to a very-deep imaging technique boosting the capabilities of CFHT's wide-field optical imager MegaCam.

The Atlas3D team conducts a systematic survey of more than one hundred nearby elliptical galaxies. If the current result based on the first two galaxies is confirmed on the larger sample, i.e. faint extended features are frequently detected, the standard model for elliptical galaxies formation should be revisited.

SOFIA Airborne telescope: Makes its first observations - New Scientist

Airborne telescope makes its first observations - space - 28 May 2010 - New Scientist

SOFIA snapped this composite infrared image of Jupiter (right) during its first flight as a working observatory. The white stripe shows a region of relatively transparent clouds that reveal the planet's warm interior (Image: NASA)

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A jet with a large telescope built into its side has snapped its first in-flight images of the night sky. The flight begins a new phase for the infrared observatory, called SOFIA, which was once in danger of cancellation due to cost overruns.

The Stratospheric Observatory for Infrared Astronomy (SOFIA) is a Boeing 747 jet that has been modified to carry a 2.5-metre telescope provided by the German Space Agency. The observatory is designed to fly at an altitude of about 12 kilometres.

That altitude is above more than 99 per cent of the atmosphere's water vapour, which obscures the sky at infrared wavelengths. That means SOFIA will receive roughly 80 per cent of the infrared light that hits orbiting space telescopes. It can be used to study phenomena such as star and planet formation in the Milky Way.

The telescope took off on Wednesday from NASA's Dryden Flight Research Center in Palmdale, California, for its first in-flight night observations. Images taken during the six-hour flight are sharp enough for the telescope to perform "front-line astronomical research", SOFIA project scientist Pam Marcum said in a statement.

SOFIA, which cost more than $1 billion to develop, was nearly cancelled due to delays and cost overruns. NASA decided to restore funding to the project in 2006, after criticism from astronomers and a technical review that said the project faced no insurmountable challenges.

NASA aims to fly SOFIA several times a week for about 20 years.