Gamma-ray vision: tracing the extremes in extragalactic astrophysics
Prof. Lucy Fortson
University of Minnesota
Imaging Air Cherenkov Telescopes such as VERITAS, detect gamma rays with energies 10^12 times greater than optical photons. Over the past 15 years we have detected ~300 sources of such photons, about a third of which are radio-loud Active Galactic Nuclei (AGN). These AGN emit radiation spanning the entire electromagnetic spectrum, varying in intensity over a wide range of timescales, from minutes to years. The emission comes from jets of relativistic particles extending to kiloparsec and even megaparsec scales. Understanding these cosmic particle accelerators requires information from both simultaneous observations of flares and long-term monitoring campaigns. In this talk, I will focus on several examples of VERITAS-detected radio-loud AGN, and associated multi-wavelength analyses, to provide a snapshot of what we are learning about the location of gamma-ray emitting regions in the jet, and whether a population of extreme blazars exists. I will close with a few words about the upcoming Cherenkov Telescope Array Observatory and the importance of gamma-ray observatories in the multi-messenger era.