Detection of starlight from far-away galaxies with quasars achieved by JWST for the first time.

CAMBRIDGE, MASS. — Astronomers have detected starlight from distant galaxies hosting extremely bright supermassive black holes called quasars for the first time, according to data from the James Webb Space Telescope. Astronomers reported at the JWST First Light meeting on June 12 that four of the galaxies are large, compact, and possibly disk-shaped. Studying the galaxies could help solve the mystery of how black holes in the early universe grew so quickly. Quasars are black holes that heat swallowed material to white-hot temperatures, causing them to shine more brightly than the stars in their galaxies. They are so bright and far away that they present themselves as single starlike points of light.

Two independent groups used that starlike quality to erase the glow from the images of their galaxies, quite like a sculptor coaxing a figure out of marble. The teams used the stars in the images to simulate the shapes of the quasars and then subtracted the simulated quasar from the image of each whole galaxy, resulting in only starlight remaining.

Yue and colleagues observed six quasar-hosting galaxies and Ding and colleagues at the Kavli Institute for the Physics and Mathematics of the Universe in Tokyo used JWST to look at a pair of quasars. The light from all the quasars was emitted more than 12.8 billion years ago, or less than a billion years after the Big Bang.

All the measured galaxies appear to be less than a tenth as wide as the Milky Way, measuring between 2,600 and 8,000 light-years across. The two galaxies that Yue and colleagues observed contain enough stars to make up between 10 billion and 100 billion times the mass of the sun, the researchers estimate. The pair that Ding and colleagues looked at weigh in at about 25 billion and 63 billion solar masses.

The mass calculations might prove to be overestimates, according to astrophysicist Paul Shapiro of the University of Texas at Austin, who was not involved in either study. Converting the light that JWST can see into stars rests on assumptions about how many stars of various masses a galaxy has.

“The fact that we can see [the host galaxies] at all is very exciting,” says astronomer Madeline Marshall of the National Research Council Canada in Victoria. The fact that two groups are reporting starlight from quasar hosts independently is very convincing, she says.

JWST is scheduled to observe at least 10 more quasars, some of which are even farther away, providing a larger sample that could help astronomers to understand enduring cosmic riddles about how black holes and galaxies interact as they grow.

“We don’t know how black holes can be so big in the early universe,” Ding says. “You need to understand the environment of this monster, how it can collect so much matter to it. So knowing the conditions — the mass of the host galaxies, for example — at least then you can say how their local environment is.”

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