BLACK HOLES CAN BOOST STAR FORMATION IN SATELLITE GALAXIES
Astronomers have long observed that supermassive black holes lurking at the centers of galaxies can halt star formation. These behemoths blast their surroundings with high-energy radiation, disrupting clouds of potential star-forming material and heating them so they can’t condense into new suns. But new research published June 9 in Nature paints a different picture. In some cases, supermassive black holes can instead facilitate star formation — not in the host galaxy, but in the small satellite galaxies that orbit their host galaxy.
The study looked at galaxies that are just joining a cluster. In such groups, the space between galaxies is filled with hot gas, called the intracluster medium. As a galaxy and its satellites move through the cluster, this gas acts like a headwind, stripping away star-forming material and slowing the birth rate of new stars. This is called quenching.
Researchers expected
BLOWING BUBBLES.
that when entering a cluster, satellite galaxies of a host galaxy with an active supermassive black hole should experience more quenching, as the black hole bombards the satellites with radiation and the intracluster medium strips away any remaining star-forming fuel. But observations of 30,000 galaxy groups and clusters showed that satellite galaxies orbiting above or below the plane of their host galaxy were actually 5 percent less likely to experience quenching. Simulations corroborated the find with similar outcomes.
The team believes the counterintuitive result occurs because the black hole’s jets clear away some of the intracluster gas in a bubble around the galaxy and its satellites. Satellite galaxies in the right location within this bubble thus don’t experience hot-gas headwinds, which in turn reduces quenching. The result demonstrates the profound influence of supermassive black holes on their environment.