Astronomers Spy the Raw Material of Galaxy Formation: Birthing Stars

When galaxies form, they use raw materials to birth the very first of their stars. Now, scientists have discovered this raw material that was used to form galaxies when the Universe was just three billion years old--less than a quarter of its current age.

Young stars are partly formed with cold molecular hydrogen gas, H2. This gas can't be detected directly, but its presence is revealed by a 'tracer' gas, carbon monoxide (CO). This gas emits radio waves which can then be examined with instruments.

In this case, the astronomers employed CSIRO's Australia Telescope Compact Array in order to detect this material. They used the telescope to study a massive, distant conglomerate of star-forming "clumps" or "proto-galaxies" that are in the process of coming together as a single massive galaxy. This structure, called the Spiderweb, lies more than ten thousand million light-years away.

It turns out that the Spiderweb possesses at least sixty thousand million times the mass of the Sun in the form of molecular hydrogen gas. This gas is spread over a distance of almost a quarter of a million light-years, and acts as the fuel for the star-formation seen across the area. It's enough material to keep star formation going for at least another 40 million years.

The scientists weren't done yet, though. In another set of studies, they measured CO in two very distant galaxies. The faint radio waves from these galaxies were amplified with a technique called gravitational lensing, which essentially acts like a magnifying glass to allow researchers to see more distant galaxies. This allowed them to make an estimate of how rapidly the galaxy is forming stars.

The findings could allow researchers to better understand the process of galaxy formation. In addition, it opens the way to studying how early galaxies made their first stars.

The findings are published in the journal Monthly Notices of the Royal Astronomical Society.