WoU-MMA: Gamma-Ray Astrophysics and Cosmic-ray Physics with HAWC (UW-Madison Group Grant)

The understanding of the origin of ultra high-energy particles and light is one of the central challenges in contemporary astronomy and astrophysics. It is a study that will lead us to a better understanding of the dynamics of the cosmos. The High-Altitude Water Cherenkov Observatory (HAWC), a technologically advanced gamma-ray and cosmic-ray detector located on the slopes of Sierra Negra volcano in Mexico, is among the most sensitive gamma-ray observatories in the world. Since 2015, HAWC has accumulated high-quality data sets of gamma rays and cosmic rays from the Northern sky. This project will study high energy gamma rays and cosmic rays recorded by HAWC, with the goal to uncover the nature of extreme astrophysical objects that emit light at energies of trillions of electron volts (TeV). These studies will contribute to our understanding of particle acceleration and its propagation in space. In parallel to advancing scientific knowledge, this project prepares students across educational levels to join the national science and technology workforce. The project will bring the excitement of this research to the public through outreach activities. Taking advantage of HAWC's new data pass and by implementing advanced analysis algorithms, these gamma-ray studies will tackle important questions of gamma-ray astrophysics. A central focus is the investigation of TeV halos, which are extended gamma-ray structures surrounding middle-aged pulsars. The research will involve identifying new TeV halos, characterizing their morphology and spectral properties, and interpreting these findings in the context of local particle injection and diffusion in pulsar environments. Additionally, the team will analyze HAWC's cosmic-ray data to measure and interpret anisotropies in the arrival direction distribution of Galactic cosmic rays. These complementary studies aim to improve our understanding of particle acceleration mechanisms, transport processes, and their role in shaping the high-energy universe. This project advances the objectives of "Windows on the Universe: the Era of Multi-Messenger Astrophysics", one of the 10 Big Ideas for Future NSF Investments. 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.