For many years, astronomers have been trying to explain how it is that dwarf galaxies, the small companions around more massive systems, tend to have less mass and less stars at their cores. Traditionally, it's the other way around, with massive galaxies such as the Milky Way featuring a core that is both more massive, and more magnetically active than any other region. But now, using the cold dark matter model and advanced knowledge of how stars form, experts have managed to determine the cause behind the mystery, Space
One thing that astrophysicists believe all galaxies – regardless of size – have in common is the fact that they form inside cradles of dark matter, which is the invisible stuff believed to be making up about a quarter of everything in the Universe. This type of matter cannot be viewed directly yet, but its existence has been inferred from the gravitational tug it exerts on normal matter.
Still, even with this knowledge, previous computer models have determined that the lack of matter in dwarf galaxies' cores cannot be explained. The group behind the new study reveals that one possible explanation for why all other researches failed is the fact that the models failed to account for the way stars were formed.
Until now, all computer models seeking to relate dark matter to the peculiarities of dwarf galaxies have featured only a basic description of how stars form inside these space structures, and where. “Most previous work included only a simple description of how and where stars formed within galaxies, or neglected star formation altogether. Instead we performed new computer simulations, run over several national supercomputing facilities, and included a better description of where and how star formation happens in galaxies,” University of Washington astronomer Fabio Governato revealed.
“The cold dark matter theory works amazingly well at telling where, when and how many galaxies should form. What we did was find a better description of processes that we know happen in the real Universe, resulting in more accurate simulations,” the expert added. Governato said that one of the factors that made an enormous difference in the models was the introduction of stellar winds, which were almost never considered in similar studies. These winds occur when a star explodes into a supernova, and they are known to swipe throughout the cocoons of dust and gas around, preventing stellar formation inside the nursery.
Yale University astronomer Marla Geha, who was not directly involved in the new investigation, wrote in an essay accompanying the finds that the UW team still had a long way to go before it could claim it found everything it needed to know about dwarf galaxies. However, she added that the headway made until that point in time was substantial. “A strong hint that this team is heading in the right direction is visually evident – images of their simulated galaxies are nearly indistinguishable from the real thing,” she explained.