WoU-MMA: Luminous Supermassive Black Hole Accretion Systems as High-Energy Neutrino Factories

Northwestern University, Evanston IL

Investigators

Abstract

For the past decade, NSF's Ice Cube observatory located in Antarctica has been on the hunt for energetic neutrinos. To make neutrinos, you need to smash small, subatomic particles together at near light speeds. While scientists have known this for a while, where nature hides its neutrino factories has remained a mystery. Recently, the decade-long pursuit led scientists to the galaxy TXS 0506+056. This galaxy emitted high-energy neutrinos alongside a pulse of light. Despite finding the galaxy, the scientists still do not understand what makes it into a neutrino factory. Using a computer code the researchers plan to develop, they will recreate the central regions of this galaxy inside of the world's largest supercomputers. They will then look inside of the cyber-galaxy for any places where particles accelerate and smash together. They will catalog all such places and identify those that emit both neutrinos and light, matching the observations of the real galaxy. This will help us to reveal the secrets of how and where nature makes energetic neutrinos and light, enabling the scientists around the world to better understand nature's neutrino factories. The PI will bring experiments into a local high-school and will involve high-school students in real-world data analysis and visualization. Students will gain experience working with Big Data, and they will set up in-class physical experiments. Neutrino production sites and their physical conditions are poorly understood. The fact that one high-energy neutrino was detected simultaneously with a gamma-ray flare suggested that both messengers originate in the same region, likely inside the relativistic jet. The discovery of roughly a dozen of high-energy neutrinos from the direction of TXS 0506+056 within ~6 months without any accompanying gamma-ray flare complicates the picture, as it implies that neutrinos and gamma-rays are not produced co-spatially.  Some questions to be answered include: What is the structure of radiative tilted thin disks around black holes? Where are the dissipation regions in such flows? What are the production sites of high-energy neutrinos? Are they produced via photo-hadronic or hadro-nuclear interactions? Why do most of the neutrinos coming from the direction of TXS 0506+056 have no bright electromagnetic counterpart? How do luminous accretion flows manage to produce powerful radio jets, defying the standard expectation that such disks are jet-phobic? What is the spectrum and variability of such flows? Understanding these issues will allow the scientific community to meaningfully and quantitatively interpret multi-messenger observations of black hole accretion. This award addresses/advances the goals of the Windows on the Universe Big Idea. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.