Researchers have discovered that powerful cosmic winds emerging from supermassive black holes in the center of dwarf galaxies may have a significant impact on the expansion and evolution of these galaxies by suppressing star formation. Small galaxies having stars between 100 million to a few billion are classified as dwarf galaxies and they are the most abundant type the universe. However, the Milky Way has around 200-400 billion stars. The Sloan Digital Sky Survey has mapped more than 35 percent of the sky to find 50 dwarf galaxies and researchers have used its data to find that 29 of them have shown signs of having black holes in their centers. The team of astronomers, including those from the University of California Riverside in the United States, was surprised by the strength of the detected winds.
According to the study – published in The Astrophysical Journal – researchers found that cosmic winds are emerging from the active black hole centres of six of these 29 galaxies. These winds are specifically the high-velocity flow of ionized gas. The scientists managed to measure specific properties of these winds, such as their power source, kinematics, and distribution for the first time. Gabriela Canalizo, a professor of physics and astronomy at the University of California Riverside, said that the winds were stronger than they had anticipated. Gabriela added that supermassive black holes can have a profound influence on the way large galaxies grow and age.
The two other researchers of the team are Laura V Sales, an assistant professor of physics and astronomy and Christina Manzano-King, a doctoral student in Canalizo’s lab. Manzano-King explained that dwarf galaxies are small in size because they avoid merging with others. This is why they serve as fossils which reveals the condition of the early universe. On the other hand merger of dwarf galaxies often form large galaxies. He explained that friction and strong gravitational fields heat up material as they get sucked into a black hole. This results in the release of radiative energy which pushes cosmic winds outward into intergalactic space. Researchers suspect that when the wind is pushed out, it compresses the gas ahead of the wind, increasing the rate of star formation. However, if all the wind gets expelled outwards, the availability of gas reduces and star formation could decrease. The latter phenomenon seems to be occurring in the six dwarf galaxies identified by the researchers.