Researchers Chengchao Yuan and Ruo-Yu Liu from the Chinese Academy of Sciences have recently published a study in the journal Nature Astronomy that explores the origins of high-energy emissions from a nearby galaxy, NGC 4278, and its implications for understanding the diffuse neutrino background.
NGC 4278 is a galaxy that hosts a low-luminosity active galactic nucleus (LLAGN), a type of compact region at the center of a galaxy that emits large amounts of radiation. The researchers investigated the source of the TeV (teraelectronvolt) gamma-ray emissions detected by the Large High Altitude Air Shower Observatory (LHAASO) from this galaxy. They considered two plausible scenarios for the origin of these emissions: AGN jets and winds.
The study found that the observed X-ray, GeV (gigaelectronvolt), and TeV emissions could be explained by either single-zone leptonic emission from moderately relativistic jets or lepto-hadronic emission from sub-relativistic winds. Leptonic emission involves the acceleration of electrons, which then produce gamma-rays, while lepto-hadronic emission involves the acceleration of both electrons and protons, with the protons interacting with ambient matter to produce gamma-rays. The transition from a quasi-quiet state to an active state in NGC 4278 may be driven by an enhanced accretion rate and the expansion of jets or winds.
The researchers suggest that future observations in the MeV (megaelectronvolt) and very-high-energy gamma-ray ranges could help discriminate between the leptonic and lepto-hadronic scenarios. While the neutrino flux from NGC 4278 predicted by the wind model is too low to be detected with current neutrino observatories, a lepto-hadronic wind scenario could account for the PeV (petaelectronvolt) diffuse neutrino background when considering a local LLAGN density corrected for the TeV duty cycle.
For the energy sector, this research highlights the potential of using high-energy astrophysical observations to better understand the fundamental processes driving energy production and emission in active galactic nuclei. This could have implications for the development of new energy technologies and the understanding of the universe’s energy budget. Additionally, the study’s findings could contribute to the ongoing efforts to detect and study high-energy neutrinos, which are important for advancing our knowledge of the universe’s most energetic phenomena.
The research was published in the journal Nature Astronomy.
This article is based on research available at arXiv.