Letters of Intent received in 2020

LoI 2022-2122
The multimessenger chakra of blazar jets (Non-GA Symposium)

Date: 5 December 2022 to 9 December 2022
Location: Kathmandu, Nepal
Contact: Ioannis Liodakis (jliodakis@gmail.com)
Coordinating division: Division D High Energy Phenomena and Fundamental Physics
Other divisions: Division B Facilities, Technologies and Data Science
Division C Education, Outreach and Heritage
Co-Chairs of SOC: Vasiliki Pavlidou (University of Crete)
Roger Blandford (Stanford University)
Co-Chairs of LOC: Ajay Kumar Jha (Central Department of Physics)
Dinesh Kandel (Stanford University)



particle acceleration mechanisms
jet formation, composition, and acceleration
multiwavelength variability
multiwavelength polarization
multimessenger theory and observations
origin of the high/very high energy emission
jet and magnetic field structure



Blazars are among the most intriguing and consistently bright objects in the observable Universe. They are the most extreme active galactic nuclei with powerful relativistic jets extending out to kpc from the central engine. Despite decades of systematic study of their emission across the electromagnetic spectrum, we still lack a basic understanding of their intrinsic jet processes and the processes relevant to the supermassive black holes that power them. For example, the origin of the high-energy emission in blazars jets is still a mystery, and a highly debated open question since the first detection of the jet of 3C 273 in X-rays and γ-rays in the 1970s by NASA’s HEAO A2 and ESA’S COS-B satellites. The fact that blazars host some of the largest black holes and fastest resolved jets makes them unique sites for studying extreme astrophysics and strong gravity, from the origin and cosmic evolution of supermassive black holes and their jets, to particle acceleration, and jet--inter-galactic medium interactions. Blazars are also possibly responsible for the production of cosmogenic neutrinos and ultra-high--energy cosmic rays reaching energies > 1e20 eV. Many of these interesting phenomena probe physics in regimes inaccessible to laboratories on Earth. Thus, understanding how black holes interact with their environments, as well as the consequences of such interactions, has rippling effects not only across astrophysics, but also for fundamental physics and beyond. It is becoming increasingly clear in the blazar community that understanding the emission of the jets in a broader context is necessary to advance our knowledge of their intrinsic properties.

This is the perfect time to study blazars and their jets. Advances in low-frequency radio (LOFAR), in millimeter Very Long Baseline Interferometry experiments (e.g., EHT), continued operations of Swift in X-rays and Fermi in γ-rays, IceCube in neutrinos, as well as the upcoming large-scale surveys (e.g., Simons Observatory and SKA in radio, LSST in optical-infrared, CTA in TeV γ-rays) set the ideal stage to study the multimessenger emission and structure of blazars on diverse scales. The launch of the Imaging X-ray Polarimetry Explorer in late 2021 also marks the beginning of the era of high-energy polarization.

The proposed symposium comes at the right time to recollect all that we know about blazars, all that we have yet to learn, and to organize the community and facilitate the building of new collaborations that will allow us, in this multimessenger era, to take advantage of the wealth of existing and upcoming facilities. With this symposium we plan to bring together theorists and observers working on different aspects of blazar spectra in order to find common ground and, as a community, tackle the major open questions in astrophysical jets.