Nav: Home

New for three types of extreme-energy space particles: Theory shows unified origin

January 22, 2018

New model connects the origins of very high-energy neutrinos, ultrahigh-energy cosmic rays, and high-energy gamma rays with black-hole jets embedded in their environments.

One of the biggest mysteries in astroparticle physics has been the origins of ultrahigh-energy cosmic rays, very high-energy neutrinos, and high-energy gamma rays. Now, a new theoretical model reveals that they all could be shot out into space after cosmic rays are accelerated by powerful jets from supermassive black holes.

The model explains the natural origins of all three types of "cosmic messenger" particles simultaneously, and is the first astrophysical model of its kind based on detailed numerical computations. A scientific paper that describes this model, produced by Penn State and University of Maryland scientists, will be published as an Advance Online Publication on the website of the journal Nature Physics on January 22, 2018.

"Our model shows a way to understand why these three types of cosmic messenger particles have a surprisingly similar amount of power input into the universe, despite the fact that they are observed by space-based and ground-based detectors over ten orders of magnitude in individual particle energy," said Kohta Murase, assistant professor of physics and astronomy and astrophysics at Penn State. "The fact that the measured intensities of very high-energy neutrinos, ultrahigh-energy cosmic rays, and high-energy gamma rays are roughly comparable tempted us to wonder if these extremely energetic particles have some physical connections. The new model suggests that very high-energy neutrinos and high-energy gamma rays are naturally produced via particle collisions as daughter particles of cosmic rays, and thus can inherit the comparable energy budget of their parent particles. It demonstrates that the similar energetics of the three cosmic messengers may not be a mere coincidence."

Ultrahigh-energy cosmic rays are the most energetic particles in the universe -- each of them carries an energy that is too high to be produced even by the Large Hadron Collider, the most powerful particle accelerator in the world. Neutrinos are mysterious and ghostly particles that hardly ever interact with matter. Very high-energy neutrinos, with energy more than one million mega-electronvolts, have been detected in the IceCube neutrino observatory in Antarctica. Gamma rays have the highest-known electromagnetic energy -- those with energies more than a billion times higher than a photon of visible light have been observed by the Fermi Gamma-ray Space Telescope and other ground-based observatories. "Combining all information on these three types of cosmic messengers is complementary and relevant, and such a multi-messenger approach has become extremely powerful in the recent years," Murase said.

Murase and the first author of this new paper, Ke Fang, a postdoctoral associate at the University of Maryland, attempt to explain the latest multi-messenger data from very high-energy neutrinos, ultrahigh-energy cosmic rays, and high-energy gamma rays, based on a single but realistic astrophysical setup. They found that the multi-messenger data can be explained well by using numerical simulations to analyze the fate of these charged particles.

"In our model, cosmic rays accelerated by powerful jets of active galactic nuclei escape through the radio lobes that are often found at the end of the jets," Fang said. "Then we compute the cosmic-ray propagation and interaction inside galaxy clusters and groups in the presence of their environmental magnetic field. We further simulate the cosmic-ray propagation and interaction in the intergalactic magnetic fields between the source and the Earth. Finally we integrate the contributions from all sources in the universe."

The leading suspects in the half-century old mystery of the origin of the highest-energy cosmic particles in the universe were in galaxies called "active galactic nuclei," which have a super-radiating core region around the central supermassive black hole. Some active galactic nuclei are accompanied by powerful relativistic jets. High-energy cosmic particles that are generated by the jets or their environments are shot out into space almost as fast as the speed of light.

"Our work demonstrates that the ultrahigh-energy cosmic rays escaping from active galactic nuclei and their environments such as galaxy clusters and groups can explain the ultrahigh-energy cosmic-ray spectrum and composition. It also can account for some of the unexplained phenomena discovered by ground-based experiments," Fang said. "Simultaneously, the very high-energy neutrino spectrum above one hundred million mega-electronvolts can be explained by particle collisions between cosmic rays and the gas in galaxy clusters and groups. Also, the associated gamma-ray emission coming from the galaxy clusters and intergalactic space matches the unexplained part of the diffuse high-energy gamma-ray background that is not associated with one particular type of active galactic nucleus."

"This model paves a way to further attempts to establish a grand-unified model of how all three of these cosmic messengers are physically connected to each other by the same class of astrophysical sources and the common mechanisms of high-energy neutrino and gamma-ray production," Murase said. "However, there also are other possibilities, and several new mysteries need to be explained, including the neutrino data in the ten-million mega-electronvolt range recorded by the IceCube neutrino observatory in Antarctica. Therefore, further investigations based on multi-messenger approaches -- combining theory with all three messenger data -- are crucial to test our model."

The new model is expected to motivate studies of galaxy clusters and groups, as well as the development of other unified models of high-energy cosmic particles. It is expected to be tested rigorously when observations begin to be made with next-generation neutrino detectors such as IceCube-Gen2 and KM3Net, and the next-generation gamma-ray telescope, Cherenkov Telescope Array.

"The golden era of multi-messenger particle astrophysics started very recently," Murase said. "Now, all information we can learn from all different types of cosmic messengers is important for revealing new knowledge about the physics of extreme-energy cosmic particles and a deeper understanding about our universe."
-end-
The research was partially supported by the National Science Foundation (grant No. PHY-1620777) and the Alfred P. Sloan Foundation.

CONTACTS

Kohta Murase: murase@psu.edu, (+1) 814-863-9594

Barbara Kennedy (PIO): bkk1@psu.edu, (+1) 814-863-4682

ILLUSTRATIONS

A downloadable high-resolution illustration is at https://psu.box.com/s/b1shxv1vtmtvu2eg99c2mjeai9adsy0l

CAPTION FOR ILLUSTRATION: This image illustrates the "multi-messenger'' emission from a gigantic reservoir of cosmic rays that are accelerated by powerful jets from a supermassive black hole. The high-energy cosmic rays escaping from the black hole's active galactic nucleus are trapped in the magnetized environment that serves as a reservoir of cosmic rays. The high-energy neutrinos and gamma rays are produced in the magnetized environment during their confinement and in the intergalactic space during their propagation. The ultrahigh-energy cosmic rays, high-energy neutrinos, and gamma rays eventually reach the Earth, where they can give us a unified picture of all three cumulative fluxes of the cosmic particles.

CREDIT FOR ILLUSTRATION: Kanoko Horio

ARCHIVE

After the journal's news embargo lifts, this press release will be posted online at http://science.psu.edu/news-and-events/2018-news/Murase1-2018

Penn State

Related Neutrinos Articles:

Borexino sheds light on solar neutrinos
For more than ten years, the Borexino Detector located 1,400 meters below surface of the Italian Gran Sasso massif has been exploring the interior of our Sun.
A first 'snapshot' of the complete spectrum of neutrinos emitted by the sun
About 99 percent of the sun's energy emitted as neutrinos is produced through nuclear reaction sequences initiated by proton-proton (pp) fusion in which hydrogen is converted into helium, say scientists including physicist Andrea Pocar at the University of Massachusetts Amherst.
Study of high-energy neutrinos again proves Einstein right
A new study by MIT and others proves Einstein is right again.
A blazar is a source of high-energy neutrinos
A celestial object known as a blazar is a source of high-energy neutrinos, report two new studies.
Blazar accelerates cosmic neutrinos to highest energies
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos.
Origin of neutrinos proved by Drexel University astrophysicist, IceCube colleagues
With nine-and-a-half years of data and a South Pole observatory, a Drexel University professor and her colleagues has shown the origin of at least some of the high-energy particles known as 'neutrinos.'
IceCube neutrinos point to long-sought cosmic ray accelerator
An international team of scientists, with key contributions from researchers at the University of Maryland, has found the first evidence of a source of high-energy cosmic neutrinos, ghostly subatomic particles that travel to Earth unhindered for billions of light years from the most extreme environments in the universe.
University of Alabama professors help in discovery of potential cosmic ray source
Three professors at The University of Alabama are part of an international team of scientists who found evidence of the source of tiny cosmic particles, known as neutrinos, a discovery that opens the door to using these particles to observe the universe.
NOvA experiment sees strong evidence for antineutrino oscillation
The NOvA collaboration has announced its first results using antineutrinos, and has seen strong evidence of muon antineutrinos oscillating into electron antineutrinos over long distances, a phenomenon that has never been unambiguously observed.
Matter-antimatter asymmetry may interfere with the detection of neutrinos
From the data collected by the LHCb detector at the Large Hadron Collider, it appears that the particles known as charm mesons and their antimatter counterparts are not produced in perfectly equal proportions.
More Neutrinos News and Neutrinos Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

Risk
Why do we revere risk-takers, even when their actions terrify us? Why are some better at taking risks than others? This hour, TED speakers explore the alluring, dangerous, and calculated sides of risk. Guests include professional rock climber Alex Honnold, economist Mariana Mazzucato, psychology researcher Kashfia Rahman, structural engineer and bridge designer Ian Firth, and risk intelligence expert Dylan Evans.
Now Playing: Science for the People

#541 Wayfinding
These days when we want to know where we are or how to get where we want to go, most of us will pull out a smart phone with a built-in GPS and map app. Some of us old timers might still use an old school paper map from time to time. But we didn't always used to lean so heavily on maps and technology, and in some remote places of the world some people still navigate and wayfind their way without the aid of these tools... and in some cases do better without them. This week, host Rachelle Saunders...
Now Playing: Radiolab

Dolly Parton's America: Neon Moss
Today on Radiolab, we're bringing you the fourth episode of Jad's special series, Dolly Parton's America. In this episode, Jad goes back up the mountain to visit Dolly's actual Tennessee mountain home, where she tells stories about her first trips out of the holler. Back on the mountaintop, standing under the rain by the Little Pigeon River, the trip triggers memories of Jad's first visit to his father's childhood home, and opens the gateway to dizzying stories of music and migration. Support Radiolab today at Radiolab.org/donate.