Search for Extragalactic Tev-Emitting Sources

Although charged cosmic rays have been observed up to energiesexceeding 10 20 eV, their origin and acceleration mechanisms remainunknown. The study of gamma rays is an excellent opportunity tostudy cosmic rays because photons have no electric charge, andtherefore come straight to us from their original sources. Havingdetected galactic sources beyond 100 TeV, the High Altitude WaterCherenkov (HAWC) Observatory is currently the gamma-ray detectorwith the highest energy reach. Beyond our own galaxy, photons sufferattenuation in the extragalactic background light. Thus, by observingmulti-TeV emission from extragalactic sources we would be identifyingthe most powerful accelerators in the universe. We start our studyfrom a predefined list of relatively nearby extragalactic radio-emittingX-ray sources and search for very-high-energy emissions using datafrom the HAWC Observatory. If no significant excess is found, we usethe HAWC data to determine upper limits at TeV energies for eachextragalactic candidate allowing for constraints on the physicalparameters of the sources (e.g., energy cutoff, spectral index, etc.). Wealso identify possible interesting candidates for further studies.