- 4521
- EARLY UNIVERSE -
Blackholes appear too early?
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.
Why do they feed more like “normal” recent supermassive black holes
(SMBH).
-
------------------------ 4521
- EARLY UNIVERSE
- Blackholes appear too early?
-
- Today we see blackholes in galaxies that
can have upwards of millions or billions of solar masses. 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 quasar is the most distant yet found
and is seen as it was just 770 million years after the Big Bang.
-
- 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. 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, at least, 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, which is 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.
-
- 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. Early quasars were
shockingly normal. No matter in which wavelengths we observe them, quasars are
nearly identical at all epochs of the Universe.
-
- 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. Stay
tuned there is still more to learn?
-
-
July 7, 2024 EARLY
UNIVERSE - Blackholes appear too early? 4521
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--------------------- --- Sunday, July 7, 2024
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