The fastest wind from near a supermassive black hole ever measured at ultraviolet wavelengths has been discovered inside the constellation Pegasus using data from the Sloan Digital Sky Survey (SDSS), a large-scale astronomical project designed to map a fraction of the sky in unprecedented detail.
A paper describing the research, led by astronomers at York University in Toronto, Canada, and including three Penn State astronomers, published today (June 4) in the Astrophysical Journal.
"These investigations of the environments of black holes - some that have masses of a billion times that of the sun or more - are providing exciting clues about the formation and evolution of galaxies through virtually all of cosmic time," said Yasaman Homayouni, a postdoctoral scholar in astronomy and astrophysics in the Penn State Eberly College of Science and a co-author of the study.
Astronomers have known for nearly three decades that every large galaxy has a supermassive black hole at its center, with a mass that is millions to billions of times that of the sun. Matter spiraling into these black holes forms a spinning disk of gas and dust far larger than Earth's orbit around the sun and hotter than the solar surface. The most luminous of these disks of hot gas - called quasars - produce enormous amounts of radiation that can drive winds from their surfaces and can be seen across the observable universe.
"Just as a rainbow spreads the sun's light into different wavelengths - or colors - the SDSS spreads out the light from certain stars, galaxies and quasars into what we call their 'spectra,'" said Patrick Hall, professor of physics and astronomy at York University and leader of the research team. "From those spectra, with practice, students learn to spot unusual quasars. In November 2023, my student Marianna Veltri pointed out just such a quasar. The next day I looked at the quasar using software my student Zezhou Zhu had set up. Only then did I realize just how unusual this quasar was - it has gas moving towards us at 30% of the speed of light!"
The research team immediately proposed follow-up observations with the Gemini North telescope - an 8.1 meter optical/infrared telescope located at the top of a dormant volcano in Hawaii - which succeeded in confirming its record-breaking wind velocity.
"The quasar, known as J2318, can be found in the Great Square in the constellation of Pegasus," said Lucas Seaton, a graduate student at York University and first author of the paper. "In quasars, we often see winds of gas pushed away from the black hole by the light of the quasar. The wind in J2318 can be seen at ultraviolet wavelengths at velocities up to 30% the speed of light."
Even faster winds have been detected at X-ray wavelengths, but J2318 is the fastest ever discovered at ultraviolet wavelengths.
"While X-ray studies, many originally conducted at Penn State, have discovered even faster outflows, ultraviolet studies like this one have some unique advantages," said W. Niel Brandt, Evan Pugh University Professor, Eberly Family Chair Professor of Astronomy and Astrophysics and professor of physics at Penn State, a co-author of the paper. "Ultraviolet investigations generally provide higher resolution spectra allowing more detailed outflow characterization, and they can be conducted efficiently for vast samples of quasars - sometimes providing new targets for X-ray follow-up studies."
Unlike the differences in gas pressure that drive atmospheric winds on Earth, winds from quasars are pushed at least in part by light itself.
"In terms of wind speeds, the wind in J2318 could be called a category 77 hurricane," Seaton said. "Every category of hurricane is about 20% faster than the category below it. Calling it category 77 gives an idea of just how fast it is, but of course this wind is unlike anything on Earth."
Atoms in the quasar disk are accelerated when individual particles of light - called photons - bounce off or are absorbed by the atoms.
"Quasars put out so many photons that those tiny pushes add up to extreme velocities," Hall said.
This new record ultraviolet wind can be built into simulations to help refine models of galaxy formation dating as far back as the early universe, the researchers explained.
"This discovery is very exciting!" said Paola Rodríguez Hidalgo, associate professor at the University of Washington at Bothell and an author of the paper. "These extreme outflows carry incredible amounts of energy that can affect the galaxies around them. They serve as a sort of missing link: the elusive feedback between the active central regions and their host galaxies. While this process has been included in simulations of galaxy formation for decades, a lot more work needs to be done to understand it from observations and make sure the simulations handle it correctly."
The research team at Penn State also included Donald Schneider, distinguished professor of astronomy and astrophysics.
