- 4568 - SUPERNOVAE EXPLOSIONS - how early in the Universe? The first billion years of early Universe 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.
------------------------ 4568
- SUPERNOVAE EXPLOSIONS
- how early in the Universe?
-
- Today we see supermassive black holes
(SMBH) 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.
-
- 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. That is, 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.
-
- “ Infrared Deep Sky Survey” has the quasar
appearing as a faint red dot close to the center. It’s the most distant yet
found, seen as it was 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.
-
- How do these Supermassive Black Holes
form? 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, 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—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.
-
- 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.
- 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.
-
-
September 29, 2024 SUPERNOVAE
- how early in the Universe? 4568
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--------------------- --- Sunday, September 29,
2024
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