A new ‘super survey’ is producing the largest database of galaxy measurements, spanning the last five billion years of cosmic history. The International Galaxy and Mass Assembly (GAMA) project is combining data from ground-and space-based observatories to measure the ‘haloes’ of dark matter that surround galaxies.
“The Cold Dark Matter (CDM) model of cosmology makes predictions about how galaxies cluster and, in many cases, collide and merge,” says Andrew Hopkins, a GAMA team member. “Our measurements of the speeds of galaxies will reveal the distribution of dark matter, and enable us to test the CDM model.”
The Australian-built AAOmega spectrograph on the Anglo-Australian Telescope (AAT) at Siding Spring Observatory near Coonabarabran in northern New South Wales is a vital part of the project, with its ability to capture light from hundreds of galaxies at once. GAMA is revolutionising galaxy evolution studies by measuring galaxy shapes, sizes, masses, star formation rates, chemical abundances, and more.
“We’re studying almost as many galaxies [150,000] as the previous largest AAT survey [200,000], but over a smaller patch of sky, so our density is about ten times greater,” Andrew explains. “We’re getting about 1,000 galaxy spectra per square degree—previous surveys were only getting about 100.”
This means that GAMA is picking up fainter and smaller galaxies that were skipped in previous surveys. The project is about half complete. When finished, the huge data set “will be the reference point for galaxy evolution studies worldwide for the next decade,” says Andrew.