Science

Radio telescopes see more clearly when you stack up galaxies

By James Maynard , Jun 16, 2013 09:02 PM EDT

Radio telescopes will now see the Universe a little more clearly, thanks to a technique adapted for such observations at the International Centre for Radio Astronomy Research (ICRAR).

Jacinta Delhaize, a PhD candidate at the University of Western Australia, made observations of the amount of hydrogen present in distant galaxies. Using the Parkes radio telescope, the astronomer surveyed large areas of the sky, something that telescope is built to accomplish. To observe these faint signals from up to two billion light years away, Delhaize adopted a technique called "stacking," never before used for such a purpose.

As astronomers look to more distant galaxies, they are also looking backward in time. It also means that the observed galaxies are quite faint. As Delhaize began her measurements, she found that the hydrogen gas within the stellar structures was difficult to observe, due to their great distance. Therefore, she "stacked" the readings from several galaxies together to determine the average amount of hydrogen in the groupings. The readings were taken from 3,277 galaxies, observed over the course of 87 hours.

"What we are trying to achieve with stacking is sort of like detecting a faint whisper in a room full of people shouting. When you combine together thousands of whispers, you get a shout that you can hear above a noisy room, just like combining the radio light from thousands of galaxies to detect them above the background," Delhaize said

Using stacking may allow astronomers to view how the concentration of hydrogen in galaxies changed over billions of years, as well as provide information about the future of the Universe. The 87 hours of observing using the technique provided the same signal-to-noise ratio as a normal observation conducted over 37 days.

"Distant, younger, galaxies look very different to nearby galaxies, which means that they've changed, or evolved, over time. The challenge is to try and figure out what physical properties within the galaxy have changed, and how and why this has happened," Delhaize said.

It is believed that galaxies used to create stars much faster than they do today, possibly due to possessing a greater amount of hydrogen gas. However, the new observations showed no evidence that the amount of gas in galaxies was any greater two billion years ago than today.

This new way of viewing celestial objects in radio waves could be adopted in the next generations of radio telescopes, including the future Square Kilometer Array (SKA).

This new method of radio astronomy was detailed in an article published in the journal Monthly Notices of the Royal Astronomical Society.

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