EAGER: ADAPT: Time-Domain Study of the Dynamics of Relativistic Jets

Washington University, Saint Louis MO

Investigators

Abstract

Relativistic jets from active galactic nuclei are beams of particles and radiation powered by accretion of interstellar gas onto a supermassive black hole at the center of active galaxies. Jets are observed across the electromagnetic spectrum, from radio waves to gamma-ray energies. Their presence in galaxies has been shown to correlate with the formation rate of new stars. Limited knowledge of the structure and evolution of relativistic jets in active galactic nuclei at present has been described as “a major bottleneck in understanding the evolution of galaxies” in a recent report by the National Academy of Sciences. Jets are very dynamic astrophysical objects. The light emission observed from jets is often seen to drift slowly over years. Fast changes in intensity that can last weeks, days or even hours are also observed. Changes in the jet emission over time carry information about the energy of the particles (mostly electrons, positrons, and protons) that the jet plasma is made of, opening a window to understand the physical processes that make relativistic jets the most powerful particle accelerators in the Universe. This project will leverage the combined expertise of researchers in the fields of statistics, observational astrophysics, and theoretical plasma physics at Washington University in St. Louis to develop a framework of new statistical and artificial intelligence tools, computer simulations, and analytical physical models that characterize the evolution of relativistic jets over time as seen by radio, optical, and gamma-ray telescopes, and will connect it to the physical processes powering the jet dynamics. The research could enhance the understanding of the physical mechanisms underlying relativistic jets and impact physics and other disciplines. The project will have broader impacts on undergraduate and graduate teaching, the development of human resources with training and skills in astronomy and data science, and outreach activities targeting local students from underrepresented minorities in the fields of mathematics, statistics, physics, and astronomy. In the last decade, facilities such as the Owens Valley Radio Observatory and Very Large Baseline Array at radio frequencies, the Zwicky Transient Facility (optical), and the Fermi-LAT observatory (gamma rays) have produced and continue to deliver light curves with unprecedented high cadence and time coverage for bright jets from active galactic nuclei. Alongside, theoretical efforts have also progressed rapidly in recent years, increasing physicists’ understanding of the mechanisms of particle acceleration that can produce the observed high energy emission from jets, particularly through plasma simulations. Despite the progress in first-principles theoretical modeling, there is a significant gap between outputs of theoretical models and observational data. This project seeks to develop and make use of novel statistical and artificial intelligence tools to understand the main sources of the discrepancy and combine observed light curves with the state-of-the art particle-in-cell simulations to narrow the gap. As a first step, a library of simulated light curves will be generated and a novel set of new diagnostic tools for time series analysis of multivariate, irregularly spaced time domain data will be developed. Next, important features from the multi-band time series analysis will be used to characterize properties of both simulated and observed light curves, which will help to discriminate among different classes of theoretical models. 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.