Astronomers from the Massachusetts Institute of Technology (MIT) have been able to observe the elusive starlight surrounding some of the first quasars in the universe.
Distant signals, dating back more than 13 billion years to the beginning of the universe, reveal clues about how black holes and the first galaxies evolved.
Quasars are the fiery centers of active galaxies, which contain an insatiable supermassive black hole at their core. Most galaxies have a central black hole that can occasionally feed on gas and stellar debris, generating a brief burst of light in the form of a bright ring as matter spins toward the black hole.
On the other hand, quasars can consume huge amounts of matter over much longer timescales, generating an extremely bright and long-lasting ring; In fact, they are so bright that quasars are among the brightest objects in the universe.
Because they are so bright, quasars outshine the rest of the galaxy in which they reside. But the MIT team was able for the first time to detect fainter light from stars in the host galaxies of three ancient quasars.
Based on this elusive stellar light, the researchers estimated the mass of each host galaxy, compared to the mass of its central supermassive black hole. They found that in the case of these quasars, the central black holes were much larger relative to their host galaxies than their modern counterparts.
The results, published May 6 in The Astrophysical Journal, may shed light on how the first supermassive black holes became so massive despite having a relatively short cosmic time period for growth. In particular, those early massive black holes may have arisen from more massive “seeds” than modern black holes.
“After the universe was born, there were black hole seeds that then consumed matter and grew in a very short time,” study author Minghao Yu, a postdoctoral researcher at MIT’s Kavli Institute for Astrophysics and Space Research, says in a statement. “One of the big questions is understanding how these supermassive black holes can grow so massive and so quickly.”
“These black holes are billions of times more massive than the Sun, at a time when the universe is still in its infancy,” says study author Anna-Kristina Ehlers, an assistant professor of physics at MIT. “Our results indicate that in the early universe, supermassive black holes could have gained mass before their host galaxies, and the initial seeds of black holes could have been larger than today.”
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