Mystery of High-Speed Turbo-Charged Galaxies 11-Billion Light Years Distant


Looking almost 11 billion years into the past, astronomers measured the motions of stars in a very distant galaxy whirling at a speed of one million miles per hour — about twice the speed of our Sun through the Milky Way. The galaxies are a fraction the size of our Milky Way, and so may have evolved over billions of years into the full-grown galaxies seen around us today. They've spotted super-squeezed, massive, high speed galaxies — and they don't know why.

"One possibility is that we are looking at what will eventually be the dense central region of a very large galaxy," explained Marijn Franx of Leiden University in the Netherlands. "The centers of big galaxies may have formed first, presumably together with the giant black holes that we know exist in today's large galaxies that we see nearby."

"This galaxy is very small, but the stars are whizzing around as if they were in a giant galaxy that we would find closer to us and not so far back in time," says Pieter van Dokkum, professor of astronomy and physics at Yale University. It is still not understood how galaxies like these, with so much mass in such a small volume, can form in the early Universe and then evolve into the galaxies we see in the more contemporary, nearby Universe, which is about 13.7 billion years old.

"The ancestors of these extreme galaxies should have quite spectacular properties as they probably formed a huge amount of stars, in addition to a massive black hole, in a relatively short amount of time," said van Dokkum.

The first factor is that eleven billion light-years away means eleven billion years ago, which is nearly as much ago as there is.  The Universe is only about fourteen billion years old meaning that these early observations tell us about early Universal conditions.  The intense galaxies observed so far cram the mass of a "modern" galaxy into one fifth of the size, and are spinning four times faster than the Milky Way (accounting for differing radii).

What happened to these turbo-galaxies?  The leading theory is that if those existed then, and these big slow ones exist now, then they must have simply expanded until they became what we see today.  Except you don't get to use "simply" saying things about cosmological evolution, and nobody can explain exactly how things turned from one to the other — or how they formed in the first place.

The work by the international team combined data collected using NASA's Hubble Space Telescope with observations taken by the 8-meter Gemini South telescope in Chile.

According to van Dokkum, "The Hubble data, taken in 2007, confirmed that this galaxy was a fraction the size of most galaxies we see today in the more evolved, older Universe. The giant, 8-meter mirror of the Gemini telescope then allowed us to collect enough light to determine the overall motions of the stars using a technique not very different from the way police use laser light to catch speeding cars."

The Gemini near-infrared spectroscopic observations required an extensive 29 hours on the sky to collect the extremely faint light from the distant galaxy, which goes by the designation 1255-0.

"By looking at this galaxy we are able to look back in time and see what galaxies looked like in the distant past when the Universe was very young," said team member Mariska Kriek of Princeton University. 1255-0 is so far away that the Universe was only about 3 billion years old when its light was emitted.

The Daily Galaxy via NASA, ESA, and A. Feild (STScI)

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