Large Galaxies Formed Surprisingly Early

Large galaxies formed surprisingly early, a new study finds. You'd expect that a census of the farthest, earliest galaxies would feature a lot of smaller, hotter, younger, bluer galaxies, perhaps in the act of smashing into and coalescing with their neighbors.

But a new survey made using the 8-meter Hawaii telescope of the Gemini Observatory shows rather that at only a comparatively short time after the big bang the universe was already well furnished with large, reddish, mature elliptical galaxies.

The Gemini Deep Deep Survey (GDDS) trawled the poorly patrolled "Redshift Desert" region of cosmic history, the epoch roughly 3 to 6 billion years since the big bang and found instead what team member Roberto Abraham (University of Toronto) calls a "Redshift Dessert"---plenty of massive old galaxies where you'd expect few. Abraham and his colleagues reported the results at this week's meeting of the American Astronomical Society (AAS) in Atlanta.

Patrick McCarthy (Carnegie Institution) said that what the survey shows is that at a point only 4 billion years into the life of the universe there were already galaxies up to 3 billion years old. This leaves very little time for the assembly of something as big as an elliptical galaxy.

Furthermore, the galaxies in the survey possess a plentiful stock of heavier "metal" atoms, the kind that would have to be cooked up in repeated cycles of star birth and supernova. To put the question in term of galaxy demographics: how could there be so many senior citizens so early? According to Roberto Abraham, all of this should make theorists sweat. (Gemini Observatory website)