Supermassive Black Holes Stop Galaxies From Making New Stars
Source: The Atlantic
Supermassive Black Holes Stop Galaxies From Making New Stars
The bigger the black hole, the faster their host galaxies get “quenched,” according to new research.
MARINA KOREN 10:11 AM ET
The galaxies of the universe grow up kind of like we do. When they’re young, they’re very active, producing new stars out of clouds of dust at a rapid rate. As they age, the churning slows down and eventually stops. No more new stars. The galaxies settle into some relative peace and quiet.
Astronomers have long sought to figure out what exactly leads to this halt in star formation, a phenomenon known as “quenching.” Most simulations show that supermassive black holes, the mysterious objects at the center of most galaxies, must play a major part. The only way the simulations work—the only way astronomers can explain what they see in galaxies through their telescopes—is if black holes somehow contribute to the quenching.
Black holes are not picky eaters. They gobble up any material—cosmic dust or even stars—that wades into their gravitational grasp. When they feed, the material they devour heats up and glows brightly. Scientists give this stage in the life cycle of a black hole the very Star Trek–y name of active galactic nucleus, or AGN. The AGN, scientists believe, releases a bunch of energy, heating up gas in the galaxy and preventing it from cooling enough to condense into individual, brand-new stars. Eventually, this process extinguishes any new star formation.
But scientists haven’t yet nailed down observational evidence for this effect. “There’s a long battle within the community to try to understand the connection between black holes and star formation,” said Ignacio Martín-Navarro, a postdoctoral researcher at the University of California at Santa Cruz.
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Read more: https://www.theatlantic.com/science/archive/2018/01/black-holes-galaxy-formation/549476/
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Source: Nature
Black-hole-regulated star formation in massive galaxies
Ignacio Martín-Navarro, Jean P. Brodie, Aaron J. Romanowsky, Tomás Ruiz-Lara & Glenn van de Ven
Nature doi:10.1038/nature24999
Received: 23 May 2017
Accepted: 28 October 2017
Published online: 01 January 2018
Abstract
Supermassive black holes, with masses more than a million times that of the Sun, seem to inhabit the centres of all massive galaxies1,2. Cosmologically motivated theories of galaxy formation require feedback from these supermassive black holes to regulate star formation3. In the absence of such feedback, state-of-the-art numerical simulations fail to reproduce the number density and properties of massive galaxies in the local Universe4,5,6. There is, however, no observational evidence of this strongly coupled coevolution between supermassive black holes and star formation, impeding our understanding of baryonic processes within galaxies. Here we report that the star formation histories of nearby massive galaxies, as measured from their integrated optical spectra, depend on the mass of the central supermassive black hole. Our results indicate that the black-hole mass scales with the gas cooling rate in the early Universe. The subsequent quenching of star formation takes place earlier and more efficiently in galaxies that host higher-mass central black holes. The observed relation between black-hole mass and star formation efficiency applies to all generations of stars formed throughout the life of a galaxy, revealing a continuous interplay between black-hole activity and baryon cooling.
https://www.nature.com/articles/nature24999
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