"Our results also show that massive black holes have been shaping the evolution of galaxies from the very beginning."
Using the James Webb Space Telescope (JWST), astronomers
have found the most distant merger between supermassive black holes ever
detected.
The colliding black holes are at the heart of merging
galaxies that are so distant that the collision is seen as it was happening
just 740 million years after the Big Bang when the 13.8 billion-year-old
universe was a fraction of its current age.
Astronomers have long suspected that supermassive black
holes with masses millions or even billions of times that of the sun, which are
found at the heart of most large galaxies, have been responsible for driving
cosmic evolution. This new JWST finding indicates that supermassive black holes
have been in the driving seat almost since the beginning of time.
The JWST has been regularly uncovering supermassive black
holes in the infant universe, which has been a problem because the merger
process that facilitates their growth should take periods in excess of a
billion years. These results could also help solve the troubling mystery of how
supermassive black holes grew to tremendous masses so early in the history of
the universe.
 |
The galaxy system ZS7 as seen by the James Webb Space
Telescope, revealing the most distant colliding quasars ever seen. (Image
credit: ESA/Webb, NASA, CSA, J. Dunlop, D. Magee, P. G. Pérez-González, H.
Übler, R. Maiolino, et. al) |
"Our findings suggest that merging is an important
route through which black holes can rapidly grow, even at cosmic dawn,"
research leader and University of Cambridge scientist Hannah Übler said in a
statement. "Together with other Webb findings of active, massive black
holes in the distant universe, our results also show that massive black holes
have been shaping the evolution of galaxies from the very beginning."
When quasars collide
Supermassive black holes gobbling up matter sit at the heart
of what astronomers call active galactic nuclei (AGN). From their central
locations, these bright black holes power bright emissions known as quasars
that can often outshine the combined light of every star in the rest of the
galaxy around them.
These electromagnetic emissions feature characteristic
features that allow astronomers to determine they originate from feeding
supermassive black holes. These features can only be determined by telescopes
in orbit around the Earth, and to see them for the most distant quasars takes
the extremely powerful and sensitive infrared eye of the JWST.
To investigate merging quasars in the early universe, Übler
and colleagues zoomed in on a galactic system around 12 billion light-years
away called ZS7 with the JWST's
Near-InfraRed Spectrograph (NIRSpec).
"We found evidence for very dense gas with fast motions
in the vicinity of the black hole, as well as hot and highly ionized gas
illuminated by the energetic radiation typically produced by black holes in
their accretion [feeding] episodes," Übler explained. "Thanks to the
unprecedented sharpness of its imaging capabilities, The JWST also allowed our
team to spatially separate the two black holes."
 |
The JWST zooms in on a collision between quasars in the
distant galactic region ZS7 (Image credit: ESA/Webb, NASA, CSA, J. Dunlop, D.
Magee, P. G. Pérez-González, H. Übler, R. Maiolino, et. al) |
The team determined that one of the supermassive black holes
involved in this merger had a mass equivalent to around 50 million suns. While
they suspect that the second supermassive black hole has a similar mass, the
scientists couldn't conclusively confirm this because of dense gas surrounding
it.
"The stellar mass of the system we studied is similar
to that of our neighbor, the Large Magellanic Cloud," team member Pablo G.
Pérez-González, a scientist from the Centro de Astrobiología (CAB), said.
"We can try to imagine how the evolution of merging galaxies could be
affected if each galaxy had one supermassive black hole as large or larger than
the one we have in the Milky Way."
When the two supermassive black holes eventually merged,
they would have set the very fabric of space ringing with tiny ripples called
gravitational waves. These will radiate outward from the collision at the speed
of light and could possibly be detected by the next generation of gravitational
wave detectors.
This could include the first space-based system, the Laser
Interferometer Space Antenna (LISA), an arrangement of three spacecraft being
developed by NASA and the European Space Agency (ESA) and set to launch in
2035.
"The JWST's results are telling us that lighter systems
detectable by LISA should be far more frequent than previously assumed,"
the ESA's Lead Project Scientist for LISA, Nora Luetzgendorf, said. "It
will most likely make us adjust our models for LISA rates in this mass range.
This is just the tip of the iceberg."
Even before the launch of LISA, the JWST will continue to
investigate early supermassive black holes. Starting this summer, a program in
the $10 billion telescope's Cycle 3 operations will examine the relationship
between massive black holes and their host galaxies in the first billion years
after the Big Bang. This will include searching for and characterizing mergers.
This could tell scientists at what rate supermassive black
holes collide and if this is sufficient to explain their rapid growth in the
early cosmos.
Reference: Research PaperResearch Paper