- 4567 -
SUPERMASSIVE BLACKHOLES -
formed in the early universe?
- The early Universe is a
puzzling and still-unknown place. The first billion years of cosmic history saw
the explosive creation of stars and the growth of the first galaxies. It’s also
a time when the earliest known black holes appeared to grow very massive
quickly. Astronomers want to know how they grew and why they feed more like
“normal” recent supermassive black holes (SMBH).
-
-------------------- 4567 - SUPERMASSIVE BLACKHOLES - formed in the early universe?
-
- Today we see SMBH in galaxies that can have
upwards of millions or billions of solar masses sequestered away. Astronomers
naturally assumed that it took a long time for such monsters to build up. Like
billions of years. So, when JWST observed the most distant :”quasar
J1120+0641”, they expected to see an active galactic nucleus as it looked some
770 million years after the Big Bang. They expected a still-growing central
supermassive black hole. They were intrigued to find that it had a mass of at
least a billion suns.
-
- This ULAS J1120+0641 is a very distant
“quasar” powered by a black hole. The
quasar appears as a faint red dot close to the center. This quasar is the most
distant yet found and is seen as it was just 770 million years after the Big
Bang.
-
- That raised a question: how could such an
early SMBH get so big so fast? For something that young, having that much mass
says something about its feeding mechanism. Astronomers already know that SMBH
existed early in cosmic time. These structures at the hearts of those distant
quasars apparently already existed when the Universe was very young, about 5%
of its current age.
-
- The growth of SMBH in the early Universe is
a hot topic these days. The standard idea for a long time was that they grew
slowly through mergers and acquisitions during galaxy formation. Since those
mergers take a long time, millions of years.
It seemed that the black holes would go along for the long, slow ride.
-
- And, you can’t speed up black hole growth
too much once one forms. As matter swirls into the black hole, it does so
through the accretion disk that feeds it. The disk—the active galactic
nucleus—is very bright due to the radiation emitted as the matter heats up
through friction and magnetic field interactions. The light pressure pushes
stuff away. That limits how quickly the black hole can eat.
-
- Still, astronomers found these early SMBH
sporting 10 billion solar masses when, by conventional wisdom, they should have
been less massive. For J1120+0641,
astronomers considered different scenarios for its growth, including a
so-called “ultra-effective feeding mode”.
-
- That implies early SMBH had some very
efficient way of accreting gas and dust and other material. So, astronomers
looked at these active galactic nuclei at the hearts of distant quasars in more
detail using JWST. It has the MIRI spectrograph that looks at the light from
those quasars in great detail.
-
- The MIRI spectra of “J1120+0641” revealed
the presence of a large dust torus (a donut-shaped ring) surrounding the
accretion disk of the SMBH. That disk is feeding the SMBH at a very “normal”
rate similar to SMBH in the “modern” Universe. The quasar’s broad-line region,
where clumps of gas orbit the black hole at speeds near the speed of light look
normal, too.
-
- By almost all the properties that can be
deduced from the spectrum, J1120+0641 turns out to be feeding no differently
than quasars at later times. So, what does that mean for theories of SMBH
formation in the early Universe? The
observations rule out fast feeding and other explanations for why the SMBH is
so massive.
-
- Overall, the new observations only add to
the mystery: early quasars were shockingly normal. No matter in which
wavelengths we observe them, quasars are nearly identical at all epochs of the
Universe.
-
- If you extrapolate these observations to
other ideas about early SMBH, it means the process of black hole growth was
pretty much set early in cosmic history. They didn’t start as stellar-mass
black holes that got big. Instead, they formed from the collapse of very
massive early clouds of gas to become massive primordial seeds.
-
- From there, not only did they feed from
their accretion disks, but probably did grow even more massive through those
mergers and acquisitions. Thanks to JWST, however, astronomers now know that
the early feeding mechanisms were already in place very early in cosmic time.
Now they just need to figure out when the primordial seeds of SMBH first
appeared in the infant Universe.
-
-
September 28, 2024 SUPERMASSIVE BLACKHOLES
- in the early universe? 4567
------------------------------------------------------------------------------------------
-------- Comments appreciated and Pass it on to
whomever is interested. ---
--- Some reviews are at: -------------- http://jdetrick.blogspot.com -----
-- email feedback, corrections, request for
copies or Index of all reviews
--- to:
------
jamesdetrick@comcast.net
------ “Jim Detrick” -----------
--------------------- --- Saturday, September 28,
2024
---------------------------------
No comments:
Post a Comment