Supermassive Black Holes Hidden at the Heart of Star-Birthing Galaxies
Scientists have discovered that greedy supermassive black holes may be concealed within star-birthing galaxies, shedding light on the growth of galaxies. These black holes, powered by supermassive quasars, emit incredibly bright and powerful light, often surpassing the combined light of all the stars in their surrounding galaxy. This emission occurs as the black holes consume and tear apart surrounding matter, with some of it being channeled into near-light-speed jets launched from their poles.
However, these quasars can be challenging to detect from Earth due to the obscuration caused by the gas and dust of the surrounding galaxies. Previously, it was believed that the only way galaxies could hide quasars was through a thick ring of dust, or a torus, near the feeding supermassive black hole. This new research reveals that some galaxies can “bury” quasars using more distant material.
“The light emitted from quasars also interacts with material further out in the host galaxy, contrary to previous assumptions that most of this interaction occurred with material feeding the central super black hole,” explained research leader Carolina Andonie from Durham University’s Center for Extragalactic Astronomy in the U.K. “The discovery of this quasar-blocking dust was unexpected.”
To investigate the presence of these shrouded quasars, the team observed a sample of “dusty quasars” using the Atacama Large Millimeter Array (ALMA) in northern Chile. ALMA consists of 66 telescopes capable of peering through dust using long wavelengths of light, such as infrared or heat-emitting wavelengths.
The team found that these dusty quasars tend to be located in galaxies undergoing extreme bursts of star formation, known as “starburst galaxies.” These galaxies form a significant number of stars, sometimes more than 100 or 200 times the size of our sun each year. The high density of gas and dust within these galaxies prevents the light emitted by the quasars from escaping.
This thick material acts as a barrier, blocking visible light emissions. The only way to observe these quasars is through infrared light or X-ray emissions, although there are instances when even highly energetic X-rays cannot escape.
The study suggests that the connection between starburst galaxies and buried quasars is strongest when the central quasar is feeding rapidly and experiencing a significant growth spurt. Therefore, these buried quasars and their galaxies may represent an early stage in galactic evolution, during which young galaxies are rich in cold, dense gas and dust, enabling high rates of star formation and black hole growth.
The team’s findings indicate that there may be more quasars in the universe than previously thought, with many star-forming galaxies potentially harboring active supermassive black holes that remain hidden. The team plans to conduct further research by observing up to 60,000 quasars to confirm these results and establish a stronger connection between dusty quasars and starburst galaxies.
A paper detailing the team’s research was published on October 6 in the Monthly Notices of The Royal Astronomical Society.
