6/21/23, 9:09 PM
NEWS
In a first, JWST detected starlight from distant galaxies with quasars
ASTRONOMY
In a first, JWST detected starlight from distant galaxies with quasars
Sizing up these galaxies could help reveal how some black holes got so big so fast
Some distant galaxies host quasars (one illustrated), supermassive black holes that eat so fast they create a bright glow that
outshines all of their galaxies’ stars.
NASA, ESA AND J. OLMSTED/STSCI
By Lisa Grossman
JUNE 20, 2023 AT 9:00 AM
CAMBRIDGE, MASS. — For the first time, astronomers have detected
starlight from distant galaxies that host extremely bright supermassive black
holes called quasars.
Data from the James Webb Space Telescope reveal that four of these
galaxies are massive, compact and possibly disk-shaped, astronomers report
June 12 at the JWST First Light meeting. Studying the galaxies could help
https://www.sciencenews.org/article/jwst-starlight-galaxy-quasar-black-hole
1/5
6/21/23, 9:09 PM
In a first, JWST detected starlight from distant galaxies with quasars
solve the mystery of how black holes in the early universe grew so big so fast
(SN: 1/18/21).
The best of Science News - direct to your inbox.
Headlines and summaries of the latest Science News articles, delivered
to your email inbox every Thursday.
Your e-mail address
Sign Up
“Ever since the discovery of [distant] quasars, there have been studies trying
to detect their host galaxies,” said MIT astrophysicist Minghao Yue. But until
JWST’s sharp infrared eyes came along, it wasn’t possible. “This opens up
brand new windows towards finally understanding luminous quasars and
their host galaxies.”
Quasars are black holes that are feeding so furiously, the material they
gobble heats to white-hot temperatures, shining brighter than the stars in
the galaxy around them. They’re so bright and distant that each appears as a
single, starlike point of light.
Two independent groups used that starlike quality to erase the black hole
glow from images of their galaxies, like a sculptor coaxing a figure out of
marble.
Yue and colleagues used JWST to observe six quasar-hosting galaxies.
Around the same time, astrophysicist Xuheng Ding of the Kavli Institute for
the Physics and Mathematics of the Universe in Tokyo and colleagues used
JWST to look at another pair of quasars. The light from all the quasars was
https://www.sciencenews.org/article/jwst-starlight-galaxy-quasar-black-hole
2/5
6/21/23, 9:09 PM
In a first, JWST detected starlight from distant galaxies with quasars
emitted more than 12.8 billion years ago, or less than a billion years after the
Big Bang.
The teams used actual stars in the images to simulate the starlike shapes of
the quasars. Then they subtracted the simulated quasar from the image of
each whole galaxy, and voilà: Only starlight remained.
Ding’s team got a direct peek at both of their galaxies, while Yue’s team
glimpsed two of their six. All the measured galaxies appear to be less than a
tenth as wide as the Milky Way, measuring between 2,600 and 8,000 lightyears 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 team
reported at the meeting and in a study to appear in Nature.
Those masses are comparable to that of all the stars in the Milky Way, which
in total add up to roughly 60 billion times the mass of the sun. That’s
surprisingly massive for so early in the universe’s history.
What’s more, the galaxies seem to break a rule set by observations of
galaxies in the nearby universe. Locally, galaxies tend to split their mass
between stars and black holes in a predictable way: The more massive its
central supermassive black hole, the more stars a galaxy has. These galaxies
appear to pack more mass into their black hole than their amount of stars
should allow.
“At least for these luminous quasars, they really are over-massive,” Yue said.
The mass calculations might prove to be overestimates, says 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. Modern
galaxies have a lot more dim, lightweight stars than bright, hefty ones, so
astronomers typically assume that the brightest stars they see are just the tip
https://www.sciencenews.org/article/jwst-starlight-galaxy-quasar-black-hole
3/5
6/21/23, 9:09 PM
In a first, JWST detected starlight from distant galaxies with quasars
of the iceberg. But that might not have been the case 800 million years after
the Big Bang, Shapiro says.
Subscribe to Science News
Get great science journalism, from the most trusted source,
delivered to your doorstep.
SUBSCRIBE
“You’re observing the tail and inferring the dog,” he says. “If there were a
mass distribution that favors high-mass stars, you could be significantly
overestimating the mass associated with the light.”
But “the fact that we can see it 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.
“Pre-JWST, we could not detect host galaxies of [distant] quasars,” she said
at the meeting. “Now, with only the first year of observations … we can
actually detect some of these hosts for the first time.”
These first few quasar hosts are just the beginning, Ding says. JWST is
scheduled to observe at least 10 more, some of which are even farther away.
A larger sample will help astronomers figure out enduring cosmic riddles
about how black holes and galaxies influence each other 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.”
https://www.sciencenews.org/article/jwst-starlight-galaxy-quasar-black-hole
4/5
6/21/23, 9:09 PM
In a first, JWST detected starlight from distant galaxies with quasars
CITATIONS
M. Onoue. Characterization of starlight and black hole activity in z>6 low-luminosity quasars. First Light meeting,
Cambridge, Mass., June 12, 2023.
M. Yue. Detecting the host galaxies of luminous quasars at z~6. First Light meeting, Cambridge, Mass., June 12,
2023.
X. Ding et al. First detections of stellar light from quasar host galaxies at z > 6. arXiv:2211.14329. Submitted
November 25, 2022.
This article was supported by
readers like you.
Our mission is to provide accurate, engaging news of science to the
public. That mission has never been more important than it is today.
As a nonprofit news organization, we cannot do it without you.
Your support enables us to keep our content free and accessible to the
next generation of scientists and engineers. Invest in quality science
journalism by donating today.
DONATE NOW
https://www.sciencenews.org/article/jwst-starlight-galaxy-quasar-black-hole
5/5