PRESS-NEWS.org - Press Release Distribution
PRESS RELEASES DISTRIBUTION

USTC researchers revolutionize understanding of supermassive black hole accretion radiation in quasars

2023-10-06
(Press-News.org)

Associate Professor CAI Zhenyi and Professor WANG Junxian from the Department of Astronomy at the University of Science and Technology of China (USTC) of the Chinese Academy of Sciences (CAS), through the study of the optical to extreme ultraviolet radiation generated by the accretion of supermassive black holes at the centers of quasars, have discovered that their spectral energy distribution is independent to the intrinsic brightness of quasars, overturning the traditional understanding in this field. Furthermore, their study unveils a substantial departure of the average extreme ultraviolet spectral energy distribution of quasars from the predictions of the classical accretion disk theory. This discovery challenges the classical model and provides substantial support for models that incorporate widespread accretion disk winds. The results were published online on October 5, 2023 in Nature Astronomy.

Quasars are a class of extremely bright extragalactic objects where massive supermassive black holes at their centers continuously devour the gas in the core regions of their host galaxies. The immense gravitational potential energy is released on the accretion disk formed by the gas, converting into thermal energy and electromagnetic radiation, resulting in an abnormally bright nucleus of the galaxy. Quasars are also referred to as "cosmic behemoths" due to their exceptionally high intrinsic luminosity. According to the standard accretion disk theory, accretion disks produce the well-known "big blue bump" in the spectral energy distribution, with the peak expected in the extreme ultraviolet. The larger the central black hole's mass, the lower the expected temperature of the accretion disk, and the softer the extreme ultraviolet spectrum. Observations have revealed that more luminous quasars (with larger supermassive black hole masses) exhibit relatively weaker emission lines (explained by softer extreme ultraviolet spectra), known as the famous Baldwin Effect, which appears to be consistent with the classical accretion disk model.

Associate Professor CAI Zhenyi and Professor WANG Junxian's research focuses directly on the optical-to-ultraviolet spectral energy distribution of large sample quasars. This study utilizes observational data from the ground-based SDSS and space-based GALEX, controlling for the incompleteness of the ultraviolet detection. They found that the average ultraviolet spectral energy distribution of quasars do not depend on their intrinsic brightness, which not only suggests that differences in intrinsic brightness cannot explain the Baldwin effect but also challenges the predictions of standard accretion disk theory. At the same time, the researchers propose a possible new physical origin for the Baldwin effect: more luminous quasars have weaker accretion disk temperature fluctuations, thus unable to launch more emission line clouds. 

In addition, the study corrects for the effects of intergalactic medium absorption and finds that the average extreme ultraviolet spectrum of quasars is softer than all previous research results. This discrepancy poses a significant challenge to the standard accretion disk model but aligns well with predictions from the model involving an accretion disk wind, suggesting the prevalence of disk winds in quasars.

The results of this study have broad implications for a deeper understanding of various aspects of supermassive black hole accretion physics, black hole mass growth, cosmic reionization, the origin of broad-line regions, extreme ultraviolet dust extinction, and more. In the future, satellite projects with ultraviolet detection capabilities, such as the Chinese Space Station Telescope (CSST, http://nao.cas.cn/csst/), will greatly enhance our understanding of the physical properties of quasars and similar celestial objects.

Paper link:https://www.nature.com/articles/s41550-023-02088-5

 

Contact:

Jane FAN Qiong

Tel: +86-551-63607280

E-mail:englishnews@ustc.edu.cn

END



ELSE PRESS RELEASES FROM THIS DATE:

Climate change brings earlier arrival of intense hurricanes

Climate change brings earlier arrival of intense hurricanes
2023-10-06
Intense tropical cyclones are one of the most devastating natural disasters in the world due to torrential rains, flooding, destructive winds, and coastal storm surges. New research co-authored by a University of Hawai‘i at Mānoa atmospheric scientist revealed that since the 1980s, Category 4 and 5 hurricanes (maximum wind speed greater than 131 miles per hour) have been arriving three to four days earlier with each passing decade of climate change. Their findings were published recently in Nature.  “When intense tropical cyclones occur earlier than usual, they cause unexpected problems for communities,” said Pao-Shin Chu, atmospheric ...

Ex-football players with medical and mental health conditions at higher odds of receiving premature CTE diagnosis

Ex-football players with medical and mental health conditions at higher odds of receiving premature CTE diagnosis
2023-10-06
PITTSBURGH, Oct. 4, 2023 – Former professional American football players who have medical and mental health conditions including depression, anxiety or sleep apnea are more likely to receive an unverified diagnosis of chronic traumatic encephalopathy, or CTE, compared to those without those conditions, report researchers from the University of Pittsburgh School of Medicine, Harvard University and Vanderbilt University Medical Center in Sports Medicine today. Receiving a CTE diagnosis that cannot be verified until after death could further exacerbate mental health conditions in former players due to the current lack of ...

Natural GM crops: grasses take evolutionary shortcut by borrowing genes from their neighbours

2023-10-06
New study shows grasses are taking an evolutionary shortcut by continually borrowing genes from their neighbours to grow bigger, stronger and taller The research, led by the University of Sheffield, is the first to show how frequently grasses exchange genes in the wild The naturally occurring process observed in grasses, including in some of the crops we eat, may mirror methods used to make genetically modified crops Understanding the rate is important to know the potential impact it can have on a plant’s ...

Cambridge University receives $72 million gift for habitat restoration projects across Europe’s land and seas

Cambridge University receives $72 million gift for habitat restoration projects across Europe’s land and seas
2023-10-06
Arcadia has made a major new philanthropic donation to the University of Cambridge, taking its total support for the Endangered Landscapes & Seascapes Programme to over $138 million. The Endangered Landscapes & Seascapes Programme supports the large-scale restoration of Europe’s most treasured but endangered ecosystems, enriching biodiversity while revitalising local economies.  The work recognises humanity’s dependence on healthy, functioning ecosystems - for example in preventing urban flooding, and reducing the impacts ...

New UC Davis study looks at attitudes towards political violence

2023-10-06
(SACRAMENTO, Calif.) — A small segment of the U.S. population considers violence, including lethal violence, to be usually or always justified to advance political objectives. This is according to newly published research from the UC Davis Violence Prevention Research Program (VPRP). The study provides a complex portrait of the attitudes and concerns about the state of democracy in the U.S. It also highlights the underlying beliefs that may inform the potential for violence. The study was published Sept. 29, 2023, in Injury Epidemiology. A preprint, or version that had not yet been peer reviewed, was shared online ...

Mays Cancer Center: Targeting certain molecular interactions could yield new strategies for treating prostate cancer

2023-10-06
SAN ANTONIO, Oct. 6, 2023 – Research led by Mays Cancer Center at The University of Texas Health Science Center at San Antonio (UT Health San Antonio) has discovered that altering certain molecular interactions could yield new strategies for treating prostate cancer and related diseases. The study focuses on androgen receptors (AR), which are protein molecules that help direct the development of male sexual characteristics, essentially by turning genes on or off as necessary. The researchers determined that an optimum level of ...

Low muscle mass is associated with a two-fold risk of death from heart disease in people with diabetes

2023-10-06
New research being presented at the Annual Meeting of the European Association for the Study of Diabetes (EASD) in Hamburg, Germany (2-6 Oct) shows that low muscle mass is associated with a two-fold risk of death from cardiovascular disease in individuals with diabetes. This association is independent of frailty, glycaemic control and the microvascular complications retinopathy (damage to the blood vessels of the retina) and nephropathy (kidney disease), the analysis of data on US adults found. Sarcopenia – age-related loss of muscle mass and strength – was known to be associated with cardiovascular disease (CVD) and mortality ...

Evidence on increased rates of diabetes unclear in trans people, but evidence on higher rates of cardiovascular disease clear

2023-10-06
The latest data on the metabolic problems faced by trans people are presented at a session at this year’s Annual Meeting of the European Association for the Study of Diabetes (Hamburg 2-6 October). While evidence on increased or decreased rates of diabetes among trans men and women remains unclear, the evidence that they face higher rates of cardiovascular disease continues to mount. The talk is by Dr Dorte Glintborg, Department of Endocrinology, Odense University Hospital, Denmark. “While increased rates of cardiovascular disease might normally go hand-in-hand with increased rates of diabetes, for trans men (assigned female at birth AFAB), use of testosterone ...

New study at the Alzheimer’s Center at Temple casts light on protein that could help defeat Alzheimer’s disease and increase productive lifespan

2023-10-05
Alzheimer’s disease is the most common type of dementia, a disorder of progressively worsening memory and other thinking abilities. It rose up in the ranks of leading causes of death over the past several decades. It can also limit the duration of a working career, create uncertainty in the financial planning for retirement and rob patients of enjoyment and happiness in the final years. An effective treatment against this disease could give back to the patient the decision when to retire and improve quality of life in advanced age.   Now, scientists at the Alzheimer’s Center at Temple at the Lewis Katz School of Medicine at Temple University are on the trail ...

Up-and-coming researchers vie in a 'Shark Tank'-inspired competition during the Ramona Jones Friends of BrainHealth Scientist Selection Luncheon

Up-and-coming researchers vie in a Shark Tank-inspired competition during the Ramona Jones Friends of BrainHealth Scientist Selection Luncheon
2023-10-05
On October 2, 2023, Center for BrainHealth, part of The University of Texas at Dallas, held its annual Friends of BrainHealth Scientist Selection Luncheon at the Dallas Country Club. This year was a special one, with Ramona Jones, founding BrainHealth Advisory Board member, kicking off a five-year sponsorship of the luncheon. Her five children made this sponsorship gift in her honor and surprised her with the naming for her 95th birthday in August 2023. The Friends of BrainHealth donor circle is dedicated to supporting ...

LAST 30 PRESS RELEASES:

Time alone heightens ‘threat alert’ in teenagers – even when connecting on social media

Study challenges long-held theories on how migratory birds navigate 

Unlocking the secrets of ketosis

AI analysis of PET/CT images can predict side effects of immunotherapy in lung cancer

Making an impact. Research studies a new side of helmet safety: faceguard failures

Specific long term condition combinations have major role in NHS ‘winter pressures’

Men often struggle with transition to fatherhood amid lack of targeted information and support

More green space linked to fewer preventable deaths in most deprived areas of UK

Immunotherapy drug pembrolizumab improves outcomes for patients with soft tissue sarcoma

A formula for life? New model calculates chances of intelligent beings in our Universe and beyond

Could a genetic flaw be the key to stopping people craving sugary treats?

Experts urge complex systems approach to assess A.I. risks

Fossil fuel CO2 emissions increase again in 2024

Winners of Applied Microbiology International Horizon Awards 2024 announced

A toolkit for unraveling the links between intimate partner violence, trauma and substance misuse

Can everyday physical activity improve cognitive health in middle age?

Updated guidance reaffirms CPR with breaths essential for cardiac arrest following drowning

Study reveals medical boards rarely discipline physician misinformation

New treatment helps children with rare spinal condition regain ability to walk

'Grow Your Own' teacher prep pipeline at the University of Louisiana at Lafayette funded by US Department of Education

Lab-grown human immune system uncovers weakened response in cancer patients

More than 5 million Americans would be eligible for psychedelic therapy, study finds

Children’s Hospital of Philadelphia researchers find community health workers play critical role in coordinating asthma care across home, school and community

Comprehensive Genomic Profiling leads to better patient outcomes, new joint study says  

Animated movie characters with strabismus are more likely to be villains, study finds

How retailers change ordering strategy when a supplier starts its own direct channel

Young coral use metabolic tricks to resist bleaching

Protecting tax whistleblowers pays off

Bioluminescent proteins made from scratch enable non-invasive, multi-functional biological imaging

New study links air pollution with higher rates of head and neck cancer

[Press-News.org] USTC researchers revolutionize understanding of supermassive black hole accretion radiation in quasars