Sample Size Solves Problems

Science and technology benefit one another.  New scientific theories afford new opportunities to create technology that can harness the laws of nature.  Conversely, new technologies allow for better instrumentation and unprecedented efficiency in scientific progress.  It’s a continual feedback loop, and some of the greatest challenges in science are solved simply by throwing more resources at them, or in other words, gathering more data.

Galaxies in the SAMI survey. Credit: Credit: D. Taranu (University of Western Australia), C. Foster (University of Sydney), NAOJ (the National Astronomical Observatory of Japan)

A good example of this is a relatively old problem for astronomers – determining how the spin of a galaxy affects it’s shape.  We certainly don’t want for analogies on Earth, spinning pizza, driving on a curve, frisbees.  Most people can easily understand that if you spin something it is pushed outward radially, but what of galaxies? How do the laws of physics change when working with incredibly massive structures with unseen dark matter and an incomprehensible size?

Until recently this was a difficult problem.  It’s very hard to measure the precise spin of a galaxy, and if you do, it’s hard to do it for enough galaxies to get a viable sample.  This changed with the Sydney-AAO Multi-object Integral field unit (SAMI), which measures the movement of stars and gas inside a galaxy to determine it’s spin properties.  The real benefit is that it can do this for 13 galaxies at once, giving astronomers the tool they needed to create a sample size of  845 galaxies, thrice the number of the previous study.

“This is the first time we’ve been able to reliably measure how a galaxy’s shape depends on any of its other properties — in this case, its rotation speed,” said research team leader Dr Caroline Foster of the University of Sydney, who completed this research while working at the Australian Astronomical Observatory.  Foster’s team found that faster spinning disks are flatter, and for spiral galaxies they are also more circular.  Connecting spin to shape, we can learn about a galaxy’s history as well, since their shape is dependent on their history of mergers and collisions with smaller galaxies.

The extra data gave astronomers a conclusive result, and was dependent on the advanced technology to make the data collection process more efficient.

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