April 23, 2013
A Galaxy With Extremely Efficient Star Formation
Brett Smith for redOrbit.com — Your Universe Online
Efficiency experts and green technology proponents can now look to the heavens for inspiration, as astronomers have identified a galaxy that forms stars at almost 100 percent efficiency.
A typical star formation occurs when interstellar gas clouds in a galaxy collapse and ignite. In most galaxies, only a fraction of the total gas supply will become stars. However, in the galaxy known as SDSSJ1506+54, almost all of the gas has been driven to the star-forming core, where stars are being born one after another.
"We are seeing a rare phase of evolution that is the most extreme -- and most efficient -- yet observed," Geach said.
The highly efficient galaxy stuck out as researchers scanned the sky using WISE's infrared survey. SDSSJ1506+54 is generating infrared light at a rate of over a thousand billion times the energy of our sun.
Meanwhile, Hubble's visible-light observations showed the galaxy is highly compact. With most of its light coming from a region a few hundred light-years across, scientists knew that area of space is packed with star-forming power.
"While this galaxy is forming stars at a rate hundreds of times faster than our Milky Way galaxy, the sharp vision of Hubble revealed that the majority of the galaxy's starlight is being emitted by a region with a diameter just a few percent that of the Milky Way," said Geach.
To complete the survey of this small but powerful expanse of space, the team then used the IRAM Plateau de Bure Interferometer to determine the amount of gas contained within the galaxy. The ground-based telescope found an indication of hydrogen gas in the galaxy, which is the ideal fuel for stars. Combining the data collected from the three different instruments allowed the scientists to determine the star-forming efficiency of SDSSJ1506+54.
In some star-forming regions, gas clouds are collapsing due to gravity. When the gas collapses to the point atoms are squeezed together, the resulting nuclear fusion ignites a star´s birth.
However, interstellar turbulence can halt the process, as newly formed stars can disrupt the flow of gas. The point at which gas disruption occurs is known as the theoretical maximum for star formation. SDSSJ1506+54 was found to be exactly at this point — forming stars just before the gas clouds are torn apart.
"We see some gas outflowing from this galaxy at millions of miles per hour, and this gas may have been blown away by the powerful radiation from the newly formed stars," said co-author Ryan Hickox, an astrophysicist at Dartmouth College, Hanover, N.H.
The scientists concluded they might be witnessing the galaxy in a short-lived phase of evolution, possibly caused by the merging of two galaxies.