Elliptical Galaxies Don’t Act Their Age…

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Thanks to images taken with the MegaCam camera mounted on the Canada-France-Hawaii Telescope (CFHT, CNRC/CNRS/University of Hawaii), researchers are beginning to see that elliptical galaxies just aren’t acting their age. Their initial studies are showing signs of recent merging – meaning that many could be as much as five times younger than previously thought.

We’ve been studying massive elliptical galaxies for a long time and their stripped down stellar population has always led astronomers to assume most were in the 7 to 10 billion year old age bracket. However, astronomers from CNRS, CEA, CFHT, and the Observatoire de Lyon – all members of the Atlas3D international collaboration – have been sneaking a peak at the galactic fountain of youth. According to observations done on two elliptical galaxies (NGC 680 & NGC 5557), it would appear they’ve undergone a spiral galaxy merger… one that’s happened as recently as 1 to 3 billion 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.” says the CFH team. “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.”

A sample of elliptical galaxies from the Atlas3D survey current collection, all showing clear signs of a recent collision. Image by P.-A. Duc 2011 (c) CEA/CFHT

The Atlas3D team isn’t stopping with these results and they’re looking at a survey of more than one hundred elliptical galaxies close to the Milky Way. When the samples are gathered and compared, they’ll look for more faint extended features that could spell a recent merger. It could mean we need to rethink our standard model for elliptical galaxies formation!

Maybe even ask ’em for ID…

Original News Source: CFH News.

6 Replies to “Elliptical Galaxies Don’t Act Their Age…”

  1. Yo Tammy, at the second paragraph, in the second line: “… stellar population has always lead astronomers to…”; that should be past tense led, not “lead”.

  2. I don’t like “five times younger”, Multiplying things makes them bigger not smaller. “As little as a fifth of the age previously thought” would be better

  3. I don’t like “five times younger”, Multiplying things makes them bigger not smaller. “As little as a fifth of the age previously thought” would be better

      1. This nitpicking thing seems to be catching! Looks like I’m multiplying by two myself, don’t know how that happened. I wish there was a “preview post” facility.

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