Stars affect dark matter: study

MARION LOPEZ, SCIENCENETWORK WA

"...when we look at galaxies alone, the gas and stars become relatively more important and begin to influence dark matter..." Image: Akirastock/iStockphoto The interaction of dark matter with stars and gas in individual galaxies is more complicated than previously thought, according to International Centre for Radio Astronomy Research (ICRAR). After discovering a correlation between the concentration and mass of dark matter around clusters of galaxies, Dr Alan Duffy from ICRAR found this relationship breaks down around single galaxies, like our own Milky Way. “A basic assumption that astronomers often make is that the dark matter is so dominant that we can ignore the effects of gas and stars on its dynamics. “For massive clusters of galaxies this is a good approximation and there's a nice relation that drops out of the simulations between the mass of the cluster and the dark matter concentration, in full agreement with observations. “The problem is that when we look at galaxies alone, the gas and stars become relatively more important and begin to influence the dark matter, which causes the galaxies to lie off this concentration–mass relation.” Dr Duffy says that simulating the Milky Way is extremely computationally demanding and will require the use of the EPIC supercomputer housed at Murdoch University.   Dr Duffy hopes to find the answers as to why the dark matter around galaxies like our Milky Way is different, by creating some of the most detailed galactic simulations in the world. To verify these predictions as to the nature of Dark Matter, as well as its role in the formation of galaxies, Dr Duffy says the Australian Square Kilometre Array Pathfinder (ASKAP)—prototype of the Square Kilometre Array (SKA)—is a key project. ASKAP will enable astronomers at ICRAR to survey over half a million galaxies and help to determine what dark matter is, although it will find only a fraction of the billion galaxies that the SKA will study. In fact, Dr Duffy says the SKA will take astronomers to the edge of the Universe and will therefore be crucial in unveiling the processes by which galaxies form, by looking at the very first objects that were ever fashioned in the Universe. “The hope is that through better observations of dark matter we can begin to understand the type of particle that’s making it up. “When ASKAP comes online, we’ll be able to answer a lot of questions, while probably creating more questions that we know the SKA will have the potential to answer. “By creating mock observations from the simulations I can bridge the gap between the theory of how galaxies form and the processes which make the Milky Way look like it does, and what telescopes such as ASKAP, and ultimately the SKA, will see.” interaction of dark matter with stars and gas in individual galaxies is more complicated than previously thought, according to International Centre for Radio Astronomy Research (ICRAR).