From Clemson University: “New research hints at the presence of unconventional galaxies containing two black holes”

From Clemson University

June 19, 2020

Marco Ajello
majello@g.clemson.edu
650-804-9042

Jim Melvin
jsmelvi@clemson.edu
864-784-1707

1
New research indicates that some galaxies might have two massive black holes at their centers that can emit ultra-powerful jets of energy. Credit: European Space Agency

A Clemson University scientist has joined forces with an international team of astronomers to identify periodic gamma-ray emissions from 11 active galaxies, paving the way for future studies of unconventional galaxies that might harbor two supermassive black holes at their centers.

Among astronomers, it has long been well-established that most galaxies host a black hole at their center. But galaxies hosting a pair of black holes has remained theoretical.

The results of the team’s research appeared in The Astrophysical Journal on June 19, 2020.

“In general, supermassive black holes are characterized by masses of more than a million masses of that of our sun,” said Pablo Peñil, lead author of the study and a Ph.D. student at Universidad Complutense de Madrid in Spain. “Some of these supermassive black holes, known as active galactic nuclei (AGN) have been found to accelerate particles to near the speed of light in collimated beams called jets. The emission from these jets is detected throughout the entire electromagnetic spectrum, but most of their energy is released in the form of gamma rays.”

Gamma rays, which are the most extreme form of light, are detected by the Large Area Telescope onboard NASA’s Fermi Gamma-ray Space Telescope. AGN are characterized by abrupt and unpredictable variations in brightness.

NASA/Fermi LAT


NASA/Fermi Gamma Ray Space Telescope

“Identifying regular patterns in their gamma-ray emission is like looking at the stormy sea and searching for the tiny regular set of waves caused by, say, the passage of a small boat,” Peñil said. “It becomes very challenging very quickly.”

The team accomplished the first difficult step of identifying a large number of galaxies that emits periodically over years and is trying to address the question of what is producing that periodic behavior in these AGN. Several of the potential explanations are fascinating.

“The next step will be the preparation of observational campaigns with other telescopes to closely follow up on these galaxies and hopefully unravel the reasons behind these compelling observations,” said co-author Marco Ajello, an associate professor in the College of Science’s department of physics and astronomy at Clemson University. “We have a few possibilities in mind – from lighthouse effects produced by the jets to modulations in the flow of matter to the black hole – but one very interesting solution would be that periodicity is produced by a pair of supermassive black holes rotating around each other. Understanding the relation of these black holes with their environment will be essential for a complete picture of galaxy formation.”

Thanks to a decade of Fermi-LAT observations, the team was able to identify the repetition of gamma-ray signals over cycles of a few years. On average, these emissions repeated about every two years.

“Our study represents the most complete work to date on the search for periodicity in gamma rays, a study that will be instrumental in deriving insights about the origin of this peculiar behavior,” said co-author Alberto Domínguez, Peñil’s Ph.D. supervisor in Madrid and also a former postdoctoral researcher in Ajello’s group at Clemson. “We have used nine years of continuous LAT all-sky observations. Among the more than two thousand AGN analyzed, only about a dozen stand out for this intriguing cyclical emission.”

Enlarging the limited sample of periodic emitters constitutes an important leap forward for understanding the underlying physical processes in these galaxies.

“Previously only two blazars were known to show periodic changes in their gamma-ray brightness. Thanks to our study, we can confidently say that this behavior is present in 11 other sources,” said co-author Sara Buson, a professor at University of Würzburg in Germany. “In addition, our study found 13 other galaxies with hints of cyclical emission. But to confidently confirm this, we need to wait for Fermi-LAT to collect even more data.”

See the full article here.

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

Ranked as the 27th best national public university by U.S. News & World Report, Clemson is dedicated to teaching, research and service. Founded in 1889, we remain committed both to world-class research and a high quality of life. In fact, 92 percent of our seniors say they’d pick Clemson again if they had it to do over.

Clemson’s retention and graduation rates rank among the highest in the country for public universities. We’ve been named among the “Best Public College Values” by Kiplinger magazine in 2019, and The Princeton Review named us among the “Best Value Colleges” for 2020.

Our beautiful college campus sits on 20,000 acres in the foothills of the Blue Ridge Mountains, along the shores of Lake Hartwell. And we also have research facilities and economic development hubs throughout the state of South Carolina — in Anderson, Blackville, Charleston, Columbia, Darlington, Georgetown, Greenville, Greenwood, and Pendleton.

The research, outreach and entrepreneurial projects led by our faculty and students are driving economic development and improving quality of life in South Carolina and beyond. In fact, a recent study determined that Clemson has an annual $1.9 billion economic impact on the state.

Just as founder Thomas Green Clemson intertwined his life with the state’s economic and educational development, the Clemson Family impacts lives daily with their teaching, research and service.
How Clemson got its start

University founders Thomas Green and Anna Calhoun Clemson had a lifelong interest in education, agricultural affairs and science.

In the post-Civil War days of 1865, Thomas Clemson looked upon a South that lay in economic ruin, once remarking, “This country is in wretched condition, no money and nothing to sell. Everyone is ruined, and those that can are leaving.”

Thomas Clemson’s death on April 6, 1888, set in motion a series of events that marked the start of a new era in higher education in South Carolina. In his will, he bequeathed the Fort Hill plantation and a considerable sum from his personal assets for the establishment of an educational institution that would teach scientific agriculture and the mechanical arts to South Carolina’s young people.

Clemson Agricultural College formally opened as an all-male military school in July 1893 with an enrollment of 446. It remained this way until 1955 when the change was made to “civilian” status for students, and Clemson became a coeducational institution. In 1964, the college was renamed Clemson University as the state legislature formally recognized the school’s expanded academic offerings and research pursuits.

More than a century after its opening, the University provides diverse learning, research facilities and educational opportunities not only for the people of the state — as Thomas Clemson dreamed — but for thousands of young men and women throughout the country and the world.