Beacon from the early universe
The discovery of the second-most distant quasar shakes up scientists' understanding of black hole growth

Date:
July 1, 2020
Source:
University of California - Santa Barbara
Summary:
Often described as cosmic lighthouses, quasars are luminous beacons
that can be observed at the outskirts of the Universe, providing a
rich topic of study for astronomers and cosmologists. Now scientists
have announced the discovery of the second-most distant quasar
ever found, at more than 13 billion lightyears from Earth.



FULL STORY ========================================================================== Often described as cosmic lighthouses, quasars are luminous beacons
that can be observed at the outskirts of the Universe, providing a rich
topic of study for astronomers and cosmologists. Now scientists have
announced the discovery of the second-most distant quasar ever found,
at more than 13 billion lightyears from Earth.


==========================================================================
UC Santa Barbara's Joe Hennawi, a professor in the Department of Physics,
and former UCSB postdoctoral scholars Frederick Davies and Feige Wang,
provided crucial modeling and data analysis tools that enabled this
discovery. The results are currently in preprint on ArXiv and will appear
in The Astrophysical Journal Letters.

The researchers have named the object Pōniuā'ena, which means
"unseen spinning source of creation, surrounded with brilliance" in
the Hawaiian language. It is the first quasar to receive an indigenous
Hawaiian name.

Quasars are incredibly bright sources of radiation that lie at the centers
of distant massive galaxies. Matter spiraling onto a supermassive black
hole generates tremendous amounts of heat making it glow at ultraviolet
and optical wavelengths. "They are the most luminous objects in the
Universe," Hennawi said, "outshining their host galaxies by factors
of more than a hundred." Since the discovery of the first quasar,
astronomers have been keen to determine when they first appeared in
our cosmic history. By systematically searching for these rare objects
in wide-area sky surveys, astronomers discovered the most distant
quasar (named J1342+0928) in 2018 and now the second-most distant, Pōniuā'ena (or J1007+2115).

The team first detected Pōniuā'ena as a possible quasar after
combing through large area surveys. In 2019, the researchers observed
the object using the W. M. Keck Observatory and Gemini Observatory on
Mauna Kea, in Hawaii, confirming its existence and identity.



========================================================================== Pōniuā'ena is only the second quasar yet detected at a distance calculated at a cosmological redshift greater than 7.5, or 13 billion
light years from Earth. It hosts a black hole twice as large as the
other quasar known from the same era. The existence of these massive
black holes at such early times challenges current theories of how
supermassive black holes formed and grew in the young universe.

A cosmological puzzle Spectroscopic observations from Gemini and Keck
show the black hole powering Pōniuā'ena is 1.5 billion times
more massive than our Sun.

"Pōniuā'ena is the most distant object known in the universe
hosting a black hole exceeding one billion solar masses," said lead
author Jinyi Yang, a postdoctoral research associate at the University
of Arizona.

Black holes grow by accreting matter. In the standard picture,
supermassive black holes grow from a much smaller "seed" black hole,
which could have been the remnant of a massive star that died. "So it
is puzzling how such a massive black hole can exist so early in the
universe's history because there does not appear to be enough time for
them to grow given our current understanding," Davies explained.

For a black hole of this size to form this early in the universe, it
would need to start as a 10,000-solar-mass seed black hole only 100
million years after the Big Bang -- as opposed to growing from a much
smaller black hole formed by the collapse of a single star.



==========================================================================
"How can the universe produce such a massive black hole so early in
its history?" said Xiaohui Fan, at the University of Arizona. "This
discovery presents the biggest challenge yet for the theory of black
hole formation and growth in the early universe." The discovery of a
more exotic mechanism to form the seed black hole may be required to
explain the mere existence of Pōniuā'ena.

The Epoch of Reionization Current theory holds that the birth
of stars and galaxies as we know them started during the Epoch of
Reionization. Beginning about 400 million years after the Big Bang, the
diffuse matter in between galaxies went from being neutral hydrogen to
ionized hydrogen. The growth of the first giant black holes is thought
to have occurred during this time.

The discovery of quasars like Pōniuā'ena, deep in the
reionization epoch, is a big step towards understanding this process
of reionization and the formation of early supermassive black holes and
massive galaxies.

Pōniuā'ena has placed new and important constraints on the
evolution of the intergalactic medium in the reionization epoch.

"Pōniuā'ena acts like a cosmic lighthouse. As its light travels
the long journey towards Earth, its spectrum is altered by diffuse gas
in the intergalactic medium which allowed us to pinpoint when the Epoch
of Reionization occurred," said Hennawi. The modeling and data analysis
method used to infer information about the Epoch of Reionization from
these distant quasar spectra was developed in his research group at UC
Santa Barbara with Davies and Wang.

"Through University of California Observatories, we have privileged access
to the Keck telescopes on the summit of Mauna Kea, which allowed us to
obtain high quality data on this object shortly after it was discovered
using the Gemini telescope," Hennawi said.

Finding these distant quasars is a needle in a haystack
problem. Astronomers must mine digital images of billions of celestial
objects in order to find quasar candidates. "Even after you identify
the candidates, the current success rate of finding them is about 1%,
and this involves spending lots of expensive telescope time observing contaminants," Wang explained.

Fortunately, Hennawi and his group are developing machine learning tools
to analyze this big data and make the process of finding distant quasars
more efficient. "In the coming years the European Space Agency's Euclid satellite and NASA's James Webb Space Telescope will enable us to find
perhaps a hundred quasars at this distance, or farther," he said. "With
a large statistical sample of these objects we will be able to construct
a precise timeline of the reionization epoch as well as shed more light
on the black hole growth puzzle."

========================================================================== Story Source: Materials provided by
University_of_California_-_Santa_Barbara. Original written by Harrison
Tasoff. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Jinyi Yang, Feige Wang, Xiaohui Fan, Joseph F. Hennawi, Frederick B.

Davies, Minghao Yue, Eduardo Banados, Xue-Bing Wu, Bram Venemans,
Aaron J. Barth, Fuyan Bian, Konstantina Boutsia, Roberto Decarli,
Emanuele Paolo Farina, Richard Green, Linhua Jiang, Jiang-Tao
Li, Chiara Mazzucchelli, Fabian Walter. Pōniuā`ena:
A Luminous z = 7.5 Quasar Hosting a 1.5 Billion Solar Mass
Black Hole. The Astrophysical Journal, 2020; 897 (1): L14 DOI:
10.3847/2041-8213/ab9c26 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200701160132.htm

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