J043947.08+163415.7
Astronomers have discovered the brightest object ever seen at a time
when the universe was less than one billion years old, with the help of
NASA's Hubble Space Telescope. The brilliant beacon is a quasar, the
core of a galaxy with a black hole ravenously eating material
surrounding it.
Though the quasar is very far away — 12.8 billion light-years —
astronomers can detect it because a galaxy closer to Earth acts as a
lens and makes the quasar look extra bright. The gravitational field of
the closer galaxy warps space itself, bending and amplifying the distant
quasar’s light. This effect is called gravitational lensing.
Though researchers have searched for these very remote quasars for
over 20 years, a rare and fortuitous celestial alignment made this one
visible to them. "We don't expect to find many quasars brighter than
that in the whole observable universe," said lead investigator Xiaohui
Fan of the University of Arizona, in Tucson
.
The super-bright quasar, cataloged as J043947.08+163415.7, could hold
the record of being the brightest in the early universe for some time,
making it a unique object for follow-up studies.
Shining with light equivalent to 600 trillion Suns, the quasar is fueled by a supermassive black hole at the heart of a young galaxy in the process of forming. An immense amount of energy is emitted as the black hole consumes material around it. The detection provides a rare opportunity to study a zoomed-in image of how such black holes accompanied star formation in the very early universe and influenced the assembly of galaxies.
Besides being bright in visible and infrared wavelengths, the lensed
quasar is also bright in submillimeter wavelengths, where it was
observed with the James Clerk Maxwell Telescope on Mauna Kea, Hawaii.
This is due to hot dust heated by intense star formation in the galaxy
hosting the lensed quasar. The formation rate is estimated to be up to
10,000 stars per year (by comparison, our Milky Way galaxy makes one
star per year).
"Clearly, this black hole is not only accreting gas, but has a lot of
star formation around it," said team member Jinyi Yang at the
University of Arizona. "However, because of the boosting effect of
gravitational lensing, the actual rate of star formation could be much
lower than the observed brightness suggests," she added.
The quasar existed at a transitional period in the universe's
evolution, called reionization, where light from young galaxies and
quasars reheated the obscuring hydrogen that cooled off not long after
the big bang.
The quasar would have gone undetected if not for the power of
gravitational lensing, which boosted its brightness by a factor of 50.
However, because very distant quasars are identified by their red
color (due to absorption by diffuse gas in intergalactic space),
sometimes their light is "contaminated," and looks bluer because of the
starlight of an intervening galaxy. As a result, they may be overlooked
in quasar searches because their color is diluted to resemble that of a
normal galaxy. Fan proposes that many other remote quasars have been
missed due to this light contamination.
His team got lucky with finding J043947.08+163415.7, because the
quasar is so bright it drowns out the starlight from the especially
faint foreground lensing galaxy. "Without this high level of
magnification, it would make it impossible for us to see the galaxy,"
said team member Feige Wang of the University of California, Santa
Barbara. "We can even look for gas around the black hole and what the
black hole may be influencing in the galaxy."
The object was selected by its color by combining photometric data
from the United Kingdom Infrared Telescope Hemisphere Survey, the
Panoramic Survey Telescope and Rapid Response System (Pan-STARRS1) at
optical wavelengths, and NASA's Wide-field Infrared Survey Explorer
archive in the mid-infrared.
Follow-up spectroscopic observations were conducted by the University
of Arizona's Multi-Mirror Telescope, the Gemini Observatory and the
Keck Observatory. These observations revealed the signature of a very
faint foreground galaxy directly between the quasar and Earth that is
magnifying the quasar image. However, because the source looks fuzzy in
the ground-based observations (and so could be mistaken for only a
galaxy), the researchers used Hubble's exquisite imaging capabilities to
confirm it is a lensed quasar.
"It's a hard system to photograph because it turns out to be so
compact, which requires the sharpest view from Hubble," Fan said.
The quasar is ripe for future scrutiny. Fan's team is analyzing a
detailed 20-hour spectrum from the European Southern Observatory's Very
Large Telescope, which would show gas absorption features to identify
chemical composition and temperatures of intergalactic gas in the early
universe.
Astronomers also will use the Atacama Large
Millimeter/submillimeter Array, and eventually NASA's James Webb Space
Telescope, to look within 150 light-years of the black hole to directly
detect the influence of the black hole's gravity on gas motion and star
formation in its vicinity.
Fan will present the team's results at a press conference Jan. 9,
2019, at the 233rd meeting of the American Astronomical Society in
Seattle, Washington. The team's science paper is available online in The Astrophysical Journal Letters.
The Hubble Space Telescope is a project of international cooperation
between NASA and ESA (European Space Agency). NASA's Goddard Space
Flight Center in Greenbelt, Maryland, manages the telescope. The Space
Telescope Science Institute (STScI) in Baltimore, Maryland, conducts
Hubble science operations. STScI is operated for NASA by the Association
of Universities for Research in Astronomy in Washington, D.C.
Related Links
- The science paper by X. Fan et al.
- NASA's Hubble Portal
- Keck Observatory's Release
- Hubble-Europe's Release
- Gemini Observatory's Release
Contact
Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
410-338-4514
villard@stsci.edu
Xiaohui Fan
University of Arizona, Tucson, Arizona
520-360-0956 (cell)
520-626-7558 (office)
fan@as.arizona.edu
Source: HubbleSite/News
