WoU-MMA: Linear and Circular Polarization as a Probe of the Relativistic Jets of Blazars

This project will study blazars, the most luminous long-lived objects in the universe. Blazars are powered by matter from stars and interstellar gas clouds falling toward super-massive black holes at the centers of some galaxies. The infalling matter and rotation of the black hole create jets of high-energy particles and magnetic fields that flow outward at nearly the speed of light.

The project will help to explain (1) how the jets are formed and accelerated, (2) whether the radiating particles are mostly "normal" matter or equal amounts of matter and anti-matter, and (3) how much energy is contained in the jets. The project will utilize multi-messenger observations at different wavelengths to probe the physical conditions in the jets of nearly 40 blazars.

The project will improve our understanding of extreme conditions in the universe. It also will contribute to public appreciation of science through presentations at libraries and high schools. It will also advance the scientific training of students through visits of Native-American school students to Boston University’s Perkins Telescope, involvement of undergraduate students in the data analysis and interpretation, availability of a free textbook on extragalactic astronomy and cosmology written by the PI, and development of an exercise for college-level introductory astronomy classes. This award addresses/advances the goals of the Windows on the Universe Big Idea.

Blazars are galactic nuclei with relativistic jets of magnetized, high-energy plasma produced by actively accreting super-massive black holes. The study will provide detailed information needed to characterize the magnetic field pattern in blazar jets, which is directly related to the dynamics of the jets. This will be accomplished by measuring the polarization of blazar jets both in extremely high-resolution images at microwave frequencies of 43 and 86 GHz, and from the entire jet at visible and X-ray frequencies.

Cross-comparison of the linear polarization of blazars from millimeter-wave to X-ray wavelengths will trace the magnetic field pattern from about 10 parsecs to sub-parsec scales and test hypotheses regarding the particle acceleration processes that cause the extreme luminosities and variability of blazars. Comparison of the 43 and 86 GHz linear and circular polarization with computer simulations will facilitate a determination of both the relative amount of anti-matter (positrons) and the total kinetic power of the jets, which controls the impact that the jet can have on its galactic environment.

The amount of anti-matter determines whether the particles in the jet are produced at the base of the jet near the black hole or injected from outside the jet. The project will train undergraduate STEM students in scientific data analysis and interpretation, make available a free textbook on extragalactic astronomy and cosmology written by the PI, and develop an exercise for college-level introductory astronomy classes.

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.