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From The Eberly College of Science
At
The Pennsylvania State University
6.11.24
Media Contacts
Niel Brandt
Eberly Family Chair Professor of Astronomy and Astrophysics, Professor of Physics
wnbrandt@gmail.com
(814) 865-3509
Sam Sholtis
Science Writer
samsholtis@psu.edu
(814) 865-1390
Megan Watzke
Chandra X-ray Center, Cambridge, Massachusetts
617-496-7998
mwatzke@cfa.harvard.edu
[ https://chandra.harvard.edu/press/24_releases/press_061124.html/ ]
Combined X-ray surveys and supercomputer simulations track 12 billion years of cosmic black-hole growth.
Researchers have provided the best modeling to date of the growth of the supermassive black holes found in the centers of galaxies by combining X-ray observations from the most powerful X-ray facilities ever launched into space with supercomputer simulations of the buildup of galaxies over cosmic history. On the left is an image combining X-ray (blue) and optical (red, green, and blue) observations and on the right is simulated gas column density from cosmological simulations using IllustrisTNG. The observed X-ray emission is mainly from accreting supermassive black holes, as depicted in the artist’s illustration (inset). The length of the short-side of the figure covers the same apparent size as the full Moon in the sky. Credit: F. Zou (Penn State) et al.; Observations: The XMM-SERVS Collaboration; Simulations: The TNG Collaboration; Illustration: Nahks TrEhnl (Penn State).
By combining forefront X-ray observations with state-of-the-art supercomputer simulations of the buildup of galaxies over cosmic history, researchers have provided the best modeling to date of the growth of the supermassive black holes found in the centers of galaxies. Using this hybrid approach, a research team led by Penn State astronomers derived a complete picture of black-hole growth over 12 billion years, from the Universe’s infancy at around 1.8 billion years old to now at 13.8 billion years old.
The research comprises two papers, one published in The Astrophysical Journal in April 2024, and one as yet unpublished that will be submitted to the same journal. The results will be presented at the 244th meeting of the American Astronomical Society, held June 9 through June 13 at the Monona Terrace Convention Center in Madison, Wisconsin. The results were featured during a press conference that was livestreamed and is available to view at the AAS Press Office YouTube page.
“Supermassive black holes in galaxy centers have millions-to-billions of times the mass of the Sun,” said Fan Zou, a graduate student at Penn State and first author of the papers. “How do they become such monsters? This is a question that astronomers have been studying for decades, but it has been difficult to track all the ways black holes can grow reliably.”
Supermassive black holes grow through a combination of two main channels. They consume cold gas from their host galaxy — a process called accretion — and they can merge with other supermassive black holes when galaxies collide.
“During the process of consuming gas from their hosting galaxies, black holes radiate strong X-rays, and this is the key to tracking their growth by accretion,” said W. Niel Brandt, Eberly Family Chair Professor of Astronomy and Astrophysics and professor of physics at Penn State and a leader of the research team. “We measured the accretion-driven growth using X-ray sky survey data accumulated over more than 20 years from three of the most powerful X-ray facilities ever launched into space.”
The research team used complementary data from NASA’s Chandra X-ray Observatory, the European Space Agency’s X-ray Multi-Mirror Mission-Newton (XMM-Newton), and the Max Planck Institute for Extraterrestrial Physics’ eROSITA telescope.
In total, they measured the accretion-driven growth in a sample of 1.3 million galaxies that contained over 8,000 rapidly growing black holes.
“All of the galaxies and black holes in our sample are very well characterized at multiple wavelengths, with superb measurements in the infrared, optical, ultraviolet, and X-ray bands,” Zou said. “This allows for robust conclusions, and the data show that, at all cosmic epochs, more massive galaxies grew their black holes by accretion faster. With the quality of the data, we were able to quantify this important phenomenon much better than in past works.”
The second way that supermassive black holes grow is through mergers, where two supermassive black holes collide and merge together to form a single, even more massive, black hole. To track growth by mergers, the team used IllustrisTNG, a set of supercomputer simulations that model galaxy formation, evolution, and merging from shortly after the Big Bang until the present.
“In our hybrid approach, we combine the observed growth by accretion with the simulated growth through mergers to reproduce the growth history of supermassive black holes,” Brandt said. “With this new approach, we believe we have produced the most realistic picture of the growth of supermassive black holes up to the present day.”
The researchers found that, in most cases, accretion dominated black-hole growth. Mergers made notable secondary contributions, especially over the past 5 billion years of cosmic time for the most-massive black holes. Overall, supermassive black holes of all masses grew much more rapidly when the Universe was younger. Because of this, the total number of supermassive black holes was almost settled by 7 billion years ago, while earlier in the Universe many new ones kept emerging.
“With our approach, we can track how central black holes in the local universe most likely grew over cosmic time,” Zou said. “As an example, we considered the growth of the supermassive black hole in the center of our Milky Way Galaxy, which has a mass of 4 million solar masses. Our results indicate that our Galaxy’s black hole most likely grew relatively late in cosmic time.”
In addition to Zou and Brandt, the research team includes Zhibo Yu, graduate student at Penn State; Hyungsuk Tak, assistant professor of statistics and of astronomy and astrophysics at Penn State; Elena Gallo at the University of Michigan; Bin Luo at Nanjing University in China; Qingling Ni at the Max Planck Institute for Extraterrestrial Physics in Germany; Yongquan Xue at the University of Science and Technology of China; and Guang Yang at the University of Groningen in the Netherlands.
Funding from the U.S. National Science Foundation, the Chandra X-ray Center, and Penn State supported this work. The work was also made possible by the sharing of the IllustrisTNG simulation results with the scientific community.
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Please help promote STEM in your local schools.
The Eberly College of Science is the science college of The Pennsylvania State University, University Park, Pennsylvania. It was founded in 1859 by Jacob S. Whitman, professor of natural science. The College offers baccalaureate, master’s, and doctoral degree programs in the basic sciences. It was named after Robert E. Eberly.
Academics The Eberly College of Science offers sixteen majors in four disciplines: Life Sciences, Physical Sciences, Mathematical Sciences and Interdisciplinary Studies.
• The Life Sciences: Biology, Biochemistry & Molecular Biology, Biotechnology, Microbiology
• The Physical Sciences: Astronomy & Astrophysics, Chemistry, Physics, Planetary Science and Astronomy
• The Mathematical Sciences: Mathematics, Statistics, Data Sciences
• Interdisciplinary Programs: General Science, Forensic Science, Premedicine, Integrated Premedical-Medical, Science BS/MBA
The Pennsylvania State University is a public state-related land-grant research university with campuses and facilities throughout Pennsylvania. Founded in 1855 as the Farmers’ High School of Pennsylvania, Penn State became the state’s only land-grant university in 1863. Today, Penn State is a major research university which conducts teaching, research, and public service. Its instructional mission includes undergraduate, graduate, professional and continuing education offered through resident instruction and online delivery. In addition to its land-grant designation, it also participates in the sea-grant, space-grant, and sun-grant research consortia; it is one of only four such universities (along with Cornell University, Oregon State University, and University of Hawaiʻi at Mānoa). Its University Park campus, which is the largest and serves as the administrative hub, lies within the Borough of State College and College Township. It has two law schools: Penn State Law, on the school’s University Park campus, and Dickinson Law, in Carlisle. The College of Medicine is in Hershey. Penn State is one university that is geographically distributed throughout Pennsylvania. There are 19 commonwealth campuses and 5 special mission campuses located across the state. The University Park campus has been labeled one of the “Public Ivies,” a publicly funded university considered as providing a quality of education comparable to those of the Ivy League.
The Pennsylvania State University is a member of The Association of American Universities an organization of American and Canadian research universities devoted to maintaining a strong system of academic research and education.
Annual enrollment at the University Park campus totals more than 47,000 graduate and undergraduate students, making it one of the largest universities in the United States. It has the world’s largest dues-paying alumni association. The university offers more than 160 majors among all its campuses.
Annually, the university hosts the Penn State IFC/Panhellenic Dance Marathon (THON), which is the world’s largest student-run philanthropy. This event is held at the Bryce Jordan Center on the University Park campus. The university’s athletics teams compete in Division I of the NCAA and are collectively known as the Penn State Nittany Lions, competing in the Big Ten Conference for most sports. Penn State students, alumni, faculty and coaches have received a total of 54 Olympic medals.
Early years
The school was sponsored by the Pennsylvania State Agricultural Society and founded as a degree-granting institution on February 22, 1855, by Pennsylvania’s state legislature as the Farmers’ High School of Pennsylvania. The use of “college” or “university” was avoided because of local prejudice against such institutions as being impractical in their courses of study. Centre County, Pennsylvania, became the home of the new school when James Irvin of Bellefonte, Pennsylvania, donated 200 acres (0.8 km^2) of land – the first of 10,101 acres (41 km^2) the school would eventually acquire. In 1862, the school’s name was changed to the Agricultural College of Pennsylvania, and with the passage of the Morrill Land-Grant Acts, Pennsylvania selected the school in 1863 to be the state’s sole land-grant college. The school’s name changed to the Pennsylvania State College in 1874; enrollment fell to 64 undergraduates the following year as the school tried to balance purely agricultural studies with a more classic education.
George W. Atherton became president of the school in 1882, and broadened the curriculum. Shortly after he introduced engineering studies, Penn State became one of the ten largest engineering schools in the nation. Atherton also expanded the liberal arts and agriculture programs, for which the school began receiving regular appropriations from the state in 1887. A major road in State College has been named in Atherton’s honor. Additionally, Penn State’s Atherton Hall, a well-furnished and centrally located residence hall, is named not after George Atherton himself, but after his wife, Frances Washburn Atherton. His grave is in front of Schwab Auditorium near Old Main, marked by an engraved marble block in front of his statue.
Early 20th century
In the years that followed, Penn State grew significantly, becoming the state’s largest grantor of baccalaureate degrees and reaching an enrollment of 5,000 in 1936. Around that time, a system of commonwealth campuses was started by President Ralph Dorn Hetzel to provide an alternative for Depression-era students who were economically unable to leave home to attend college.
In 1953, President Milton S. Eisenhower, brother of then-U.S. President Dwight D. Eisenhower, sought and won permission to elevate the school to university status as The Pennsylvania State University. Under his successor Eric A. Walker (1956–1970), the university acquired hundreds of acres of surrounding land, and enrollment nearly tripled. In addition, in 1967, the Penn State Milton S. Hershey Medical Center, a college of medicine and hospital, was established in Hershey with a $50 million gift from the Hershey Trust Company.
Modern era
In the 1970s, the university became a state-related institution. As such, it now belongs to the Commonwealth System of Higher Education. In 1975, the lyrics in Penn State’s alma mater song were revised to be gender-neutral in honor of International Women’s Year; the revised lyrics were taken from the posthumously-published autobiography of the writer of the original lyrics, Fred Lewis Pattee, and Professor Patricia Farrell acted as a spokesperson for those who wanted the change.
In 1989, the Pennsylvania College of Technology in Williamsport joined ranks with the university, and in 2000, so did the Dickinson School of Law. The university is now the largest in Pennsylvania. To offset the lack of funding due to the limited growth in state appropriations to Penn State, the university has concentrated its efforts on philanthropy.
Research
Penn State is classified among “R1: Doctoral Universities – Very high research activity”. Over 10,000 students are enrolled in the university’s graduate school (including the law and medical schools), and over 70,000 degrees have been awarded since the school was founded in 1922.
Penn State’s research and development expenditure has been on the rise in recent years. According to institutional rankings of total research expenditures for science and engineering released by the National Science Foundation , Penn State stood second in the nation, behind only Johns Hopkins University and tied with the Massachusetts Institute of Technology , in the number of fields in which it is ranked in the top ten. Overall, Penn State ranked very highly nationally in total research expenditures across the board. In 12 individual fields, however, the university achieved rankings in the top ten nationally. The fields and sub-fields in which Penn State ranked in the top ten are materials, psychology, mechanical engineering, sociology, electrical engineering, total engineering, aerospace engineering, computer science, agricultural sciences, civil engineering, atmospheric sciences, and earth sciences. Moreover, in eleven of these fields, the university has repeated top-ten status every year.
The Applied Research Lab (ARL), located near the University Park campus, has been a research partner with the Department of Defense since 1945 and conducts research primarily in support of the United States Navy. It is the largest component of Penn State’s research efforts statewide, with over 1,000 researchers and other staff members.
The Materials Research Institute was created to coordinate the highly diverse and growing materials activities across Penn State’s University Park campus. With more than 200 faculty in 15 departments, 4 colleges, and 2 Department of Defense research laboratories, MRI was designed to break down the academic walls that traditionally divide disciplines and enable faculty to collaborate across departmental and even college boundaries. MRI has become a model for this interdisciplinary approach to research, both within and outside the university. Dr. Richard E. Tressler was an international leader in the development of high-temperature materials. He pioneered high-temperature fiber testing and use, advanced instrumentation and test methodologies for thermostructural materials, and design and performance verification of ceramics and composites in high-temperature aerospace, industrial, and energy applications. He was founding director of the Center for Advanced Materials (CAM), which supported many faculty and students from the College of Earth and Mineral Science, the Eberly College of Science, the College of Engineering, the Materials Research Laboratory and the Applied Research Laboratories at Penn State on high-temperature materials. His vision for Interdisciplinary research played a key role in creating the Materials Research Institute, and the establishment of Penn State as an acknowledged leader among major universities in materials education and research.
The university was one of the founding members of the Worldwide Universities Network (WUN), a partnership that includes 17 research-led universities in the United States, Asia, and Europe. The network provides funding, facilitates collaboration between universities, and coordinates exchanges of faculty members and graduate students among institutions. Former Penn State president Graham Spanier is a former vice-chair of the WUN.
The university’s library system began with a 1,500-book library in Old Main.
The university’s College of Information Sciences and Technology is the home of CiteSeerX, an open-access repository and search engine for scholarly publications. The university is also the host to the Radiation Science & Engineering Center, which houses the oldest operating university research reactor. Additionally, University Park houses the Graduate Program in Acoustics, the only freestanding acoustics program in the United States. The university also houses the Center for Medieval Studies, a program that was founded to research and study the European Middle Ages, and the Center for the Study of Higher Education (CSHE), one of the first centers established to research postsecondary education.
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