The Galactic Center Gamma-Ray Excess

Speaker: Tim Linden, Ohio State University

When: October 31, 2018 (Wed), 11:00AM to 12:00PM (add to my calendar)
Location: PRB 595

This event is part of the HET Seminar Series.

Over the last seven years, Fermi-LAT observations have convincingly found an excess in gamma-ray emission emanating from the center of the Milky Way galaxy. The excess has three definitive properties: (1) it has a hard spectrum that peaks at an energy of ~2 GeV, (2) it extends from within 0.1 degrees to more than 10 degrees from Sgr A* with a three-dimensional intensity that falls roughly as r^{-2}, (3) it is approximately spherically symmetric. Several models for this excess have been formulated, including the collective emission from a population of individually dim gamma-ray pulsars, outbursts of cosmic-ray electrons from the central molecular zone, or potentially even dark matter annihilation. In this overview, I will discuss the observational data, and the arguments for and against each theoretical model. Additionally, I will discuss significant improvements in gamma-ray diffuse emission modeling that enhance our understanding of high energy astrophysics near the Galactic center, and will describe the impact of these models on our understanding of the gamma-ray excess, and on the prospects for dark matter annihilation.