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The Mystery of the Missing Galaxies May Be Solved, Scientists Say

Jul 25, 2013 10:39 AM EDT
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Sculptor Galaxy
Three-dimensional view of ALMA observations of the outflows from the Sculptor Galaxy.
(Photo : European Southern Observatory)

Through the help of the newly-installed Atacama Large Milimeter/submilimeter Array (ALMA) in Chile, astronomers have been zeroed in on the spiral galaxy located in the southern constellation of Sculptor and, in doing so, gain a far more detailed picture of the fierce winds associated with star birth that blow out from a galaxy's core.

"With ALMA's superb resolution and sensitivity, we can clearly see for the first time massive concentrations of cold gas being jettisoned by expanding shells of intense pressure created by young stars," Alberto Bolatto of the University of Maryland and lead author of the paper, said in a press release.

As a result, the scientists were able to detect something that had not always been clear: some developing galaxies lose more gas than they take in -- a phenomenon that may have been a common occurrence in the early days of the universe.

Knowing this, the researches explain, may help explain why astronomers have detected fewer galaxies in their scan of the cosmos than simulations of the evolution of the universe suggest there should be.

Computer models, for example, show that older, redder galaxies should have considerably more mass and a larger number of stars than currently observed, according to the researchers.

The reason for this, the finding suggests, is that the galactic winds or outflow of gas are so strong they starve the galaxy of the nutrients needed to form the next generation of stars.

"These features trace an arc that is almost perfectly aligned with the edges of the previously observed hot, ionized gas outflow," noted Fabian Walter, a lead investigator at the Max Planck Institute for Astronomy in Heidelberg, Germany, and a co-author of the paper. "We can now see the step-by-step progression of starburst to outflow."

The researchers determined that molecular gas equivalent to nearly 10 times the mass of our Sun and possibly much more are ejected each year from the Sculptor Galaxy at velocities between 150,000 and almost 1,000,000 kilometers per hour -- more than actually goes into forming the galaxy's stars during the same stretch of time.

At this rate, the galaxy could run out of gas in as few as 60 million years. the scientists estimate.

"For me, this is a prime example of how new instruments shape the future of astronomy," Walter said. "We have been studying the starburst region of NGC 253 and other nearby starburst galaxies for almost ten years. But before ALMA, we had no chance to see such details.

Going forward, researchers plan on using ALMA to determine the ultimate fate of the gas carried away by the wind and, in doing so, reveal whether the starburst-driven winds are being recycled or truly removing star forming material.

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