From The Pennsylvania State University (US): “Quasars black holes and a cosmological conundrum”

Penn State Bloc

From The Pennsylvania State University (US)

January 17, 2022
Seth Palmer

A quest for the origin of the most-distant quasars in the early universe.

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Yuexing Li, associate professor of astronomy and astrophysics at Penn State. Credit: Yuexing Li. All Rights Reserved.

Astrophysicist Yuexing Li’s quest began with quasars, luminous galaxies powered by supermassive black holes actively devouring matter and releasing enormous amounts of electromagnetic radiation so hot and bright we can see it more than 13 billion light years away.

These colossal objects, formed less than a billion years after the Big Bang during a period called the Cosmic Dawn, have fascinated Li since she was a postdoc at Harvard University (US), where she was on the team that first modeled the formation of what was then the most distant known quasar.

“The most puzzling thing about these distant quasars” she said “is how did the supermassive black holes at their hearts form? Because they’re thought to weigh more than a billion suns, these black holes’ existence so early in the universe is difficult for us to explain with our theoretical models.”

The best-understood way black holes form is by the gravitational collapse of massive dying stars, which produces so-called stellar-mass black holes, with masses less than 100 times that of our sun.

These black holes may grow more massive by merging with other black holes and through a process called accretion, where surrounding matter is drawn into the black hole by its intense gravitational pull.

So could stellar-mass black holes formed by the deaths of the first stars have grown into the supermassive black holes powering those distant quasars?

Not according to recent cosmological simulations by Li and others, which point to black-hole seeds tens of thousands of times more massive.

“The consensus,” she said, “was that it’s extremely difficult, if not impossible, for those small seeds from the first stars to grow that big in that time — ten-millionfold within just a few hundred million years. But if such massive seeds were required, how could they possibly have formed?”

Critical conditions

In cosmological simulations, there’s an inherent trade-off between resolution (fineness of detail) and scale (relative size), and Li — now an associate professor of astronomy and astrophysics at Penn State — believes that trade-off may be the crux of the problem.

“A major problem with previous studies is that macroscale cosmological simulations do not have sufficient resolution to resolve the critical microscale physics of black hole growth,” she explained.

So Li developed a novel solution — combining large-scale simulations with small-scale simulations of ultrahigh resolution that would allow her to better model the formation and growth of small black holes in the early universe.

“With the unprecedented resolution of these new simulations,” she said, “I realized that some conclusions from previous papers may be only part of the story.”

Li had found the critical conditions under which those small black holes’ rate of accretion could exceed the standard limit, accelerating to what’s called super-Eddington accretion.

After inputting those conditions in her large-scale simulation, she knew she had found a solution.

“Indeed,” she said, “some of the small black holes were able to grow to a billion solar masses within a few hundred million years.”

A new frontier

Using her model — and another piece of cutting-edge code she developed, called ART2 — Li recently began a new study to discover the origin of the supermassive black holes powering the most-distant quasars.

With ART2 running on Penn State’s ROAR supercomputer, she can use her simulations to determine the likely observational properties of those first quasars, which she can then compare with existing data to make predictions for next-generation instruments like the James Webb Space Telescope (JWST).

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The Pennsylvania State University (US) ROAR Supercomputer.

National Aeronautics Space Agency(US)/European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU)/ Canadian Space Agency [Agence Spatiale Canadienne](CA) James Webb Infrared Space Telescope(US) annotated. Scheduled for launch in 2011 delayed to October 2021 finally launched December 25, 2021.

“This is a very important step to bridge the gap between simulation and observation,” she explained.

Using ART2, Li predicts that JWST, launched in December 2021, will be able to detect galaxies less than 300 million years after the Big Bang — pushing the cosmic frontier to an earlier epoch than ever before.

But even JWST, NASA’s most ambitious telescope, won’t be able to see electromagnetic radiation from small black holes at the Cosmic Dawn.

So Li is collaborating with Penn State’s LIGO group, studying gravitational waves — ripples in space-time — produced when black holes collide and merge.

“When those small black holes merge,” she explained, “the resulting gravitational waves, whose frequencies fall outside of the detection range of current ground-based observatories like LIGO, will be detectable by future observatories like LISA, the space-based gravitational-wave detector.”

Caltech /MIT Advanced aLigo

Gravity is talking. Lisa will listen. Dialogos of Eide.

European Space Agency(EU)/National Aeronautics and Space Administration (US) eLISA space based, the future of gravitational wave research.

That could enable follow-up observations in the electromagnetic spectrum and reveal an unprecedented level of detail about these mysterious objects.

“It’s like a window opening to a new world — a better understanding of how these structures formed — which will help us to understand how the universe has evolved,” Li said. “That is one of the unsolved puzzles of the early universe and, to me, one of the most exciting.”

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Penn State Campus

The Pennsylvania State University (US) 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(US), Oregon State University(US), and University of Hawaiʻi at Mānoa(US)). 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.

Annual enrollment at the University Park campus totals more than 46,800 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 km2) 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. For fiscal year 2013, according to institutional rankings of total research expenditures for science and engineering released by the National Science Foundation (US), Penn State stood second in the nation, behind only Johns Hopkins University (US) and tied with the Massachusetts Institute of Technology (US), in the number of fields in which it is ranked in the top ten. Overall, Penn State ranked 17th 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 (1st), psychology (2nd), mechanical engineering (3rd), sociology (3rd), electrical engineering (4th), total engineering (5th), aerospace engineering (8th), computer science (8th), agricultural sciences (8th), civil engineering (9th), atmospheric sciences (9th), and earth sciences (9th). Moreover, in eleven of these fields, the university has repeated top-ten status every year since at least 2008. For fiscal year 2011, the National Science Foundation reported that Penn State had spent $794.846 million on R&D and ranked 15th among U.S. universities and colleges in R&D spending.

For the 2008–2009 fiscal year, Penn State was ranked ninth among U.S. universities by the National Science Foundation, with $753 million in research and development spending for science and engineering. During the 2015–2016 fiscal year, Penn State received $836 million in research expenditures.

The Applied Research Lab (ARL), located near the University Park campus, has been a research partner with the Department of Defense (US) 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 Pennsylvania State University Libraries were ranked 14th among research libraries in North America in the 2003–2004 survey released by The Chronicle of Higher Education. The university’s library system began with a 1,500-book library in Old Main. In 2009, its holdings had grown to 5.2 million volumes, in addition to 500,000 maps, five million microforms, and 180,000 films and videos.

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.