Evidence of 200 TeV Photons from HAWC J1825-134
A. Albert, R. Alfaro, C. Álvarez, José Roberto Ángeles Camacho, J. C. Arteaga‐Velázquez, K. P. Arunbabu, D. Avila Rojas, H. A. Ayala Solares, Vardan Baghmanyan, E. Belmont‐Moreno, S. BenZvi, C. Brisbois, T. Capistrán, A. Carramiñana, S. Casanova, U. Cotti, J. Cotzomi, E. De la Fuente, R. Díaz Hernández, B. L. Dingus, M. A. DuVernois, Mora Durocher, J. C. Díaz–Vélez, K. Engel, C. Espinoza, Ke Fang, Henrike Fleischhack, N. Fraija, A. Galván-Gaméz, D. García, J. A. García-González, F. Garfias, Gwenael Giacinti, M. M. González, J. A. Goodman, J. P. Harding, B. Hona, Dezhi Huang, F. Hueyotl‐Zahuantitla, P. Hüntemeyer, A. Iriarte, A. Jardin-Blicq, Vikas Joshi, Gerd J. Kunde, A. Lara, William H. Lee, H. León Vargas, J. Linnemann, A. L. Longinotti, G. Luis-Raya, J. Lundeen, K. Malone, V. Marandon, O. Martı́nez, J. Martínez-Castro, J. A. Matthews, P. Miranda-Romagnoli, E. Moreno, M. Mostafá, A. Nayerhoda, L. Nellen, M. Newbold, M. U. Nisa, R. Noriega-Papaqui, N. Omodei, Alison Peisker, Y. Pérez Araujo, E. G. Pérez‐Pérez, Chang Dong Rho, D. Rosa‐González, H. Salazar, F. Salesa Greus, A. Sandoval, M. Schneider, Francisco Javier Zavala-Díaz de la Serna, R. W. Springer, Kirsten Tollefson, I. Torres, R. Torres-Escobedo, F. Ureña-Mena, L. Villaseñor, E. Willox, H. Zhou, C. de León
Abstract
Abstract The Earth is bombarded by ultrarelativistic particles, known as cosmic rays (CRs). CRs with energies up to a few PeV (=10 15 eV), the knee in the particle spectrum, are believed to have a Galactic origin. One or more factories of PeV CRs, or PeVatrons, must thus be active within our Galaxy. The direct detection of PeV protons from their sources is not possible since they are deflected in the Galactic magnetic fields. Hundred TeV γ -rays from decaying π 0 , produced when PeV CRs collide with the ambient gas, can provide the decisive evidence of proton acceleration up to the knee. Here we report the discovery by the High Altitude Water Cerenkov (HAWC) observatory of the γ -ray source, HAWC J1825-134, whose energy spectrum extends well beyond 200 TeV without a break or cutoff. The source is found to be coincident with a giant molecular cloud. The ambient gas density is as high as 700 protons cm −3 . While the nature of this extreme accelerator remains unclear, CRs accelerated to energies of several PeV colliding with the ambient gas likely produce the observed radiation.