The HAWC Observatory: Detecting the Highest Energy Gamma Rays Ever Observed

Abstract: 

The High Altitude Water Cherenkov (HAWC) Observatory operates continuously (>95% on-time) with a wide field-of-view (~2 sr) in order to survey approximately 2/3 of the sky each day for the highest energy gamma rays. HAWC is located at 14000' above sea level near Puebla Mexico and is the next-generation detector based on the Milagro observatory that was located at LANL’s Fenton Hill TA-57 from 2000-2008. With HAWC data from the first 17 months of operations, we have produced a map with ~ 40 sources of which about one quarter were previously unknown. Several of these sources have emission extending to > 50 TeV. Most of the sources are within the Galactic plane with the exception of two active galactic nuclei Mrk 421 and Mrk 501 that are approximately half a billion light years away. Within the region surveyed by HAWC are many dark matter rich objects, such as dwarf spheroidal galaxies, and these HAWC data place the strongest constraints to date on annihilating or decaying dark matter with masses >10 TeV. The Crab nebula is detected in this map at > 100sigma and is each day ~ 5sigma. The HAWC data are searched in real time for transient sources. HAWC monitors the same sky as gamma-ray satellites (Fermi), gravity-wave (LIGO) detectors and neutrino observatories (IceCube) allowing for multi-wavelength and multi-messenger observations.