| Description |
Telescope Array (TA) is the largest cosmic ray detector in the Northern Hemisphere, designed to measure cosmic rays with energies greater than 1018 eV. TA combines three fluorescence telescope sites, which are each instrumented with 12-14 telescopes, surrounding an array of 507 surface detectors that cover an area of roughly 300 square miles. Constructed in the high desert in Millard Country, Utah, the TA has been collecting data since 2008. There was a low energy extension added to the TA in 2013 called the Telescope Array Low-energy Extension (TALE), which allows for the observation of cosmic rays with energies as low as 1015 eV. This was done with the addition of high-elevation-angle telescopes. Elevated observation angles are needed to view the full development of the air showers since lower energy showers develop higher in the atmosphere [1]. Cosmic rays observed on Earth's surface have energies ranging from 106 to 1020 eV and those with energies over 1014 eV are sourced from other galaxies and are called Ultra- High Energy (UHE) cosmic rays. The leading candidates for the source of UHE cosmic rays are large, energetic structures where strong shocks are expected to be found. The most well-known of these are supernova remnants, which are suspected to generate cosmic rays [2]. However, it is difficult to explain the existence of cosmic rays above 1016 eV, because supernovae are not large enough to maintain acceleration for UHE particles. TA is looking for possible sources of these UHE cosmic rays to provide a better understanding of the nature of the universe. In pursuit of this goal, photons are of current interest due to the research conducted by The Tibet ASγ experiment which announced the first detection of photons with energy beyond 1014 eV. These photons were detected from the Crab Nebula and observed by many ground-based gamma-ray experiments [3]. With data collected from TA, our goal is to find photons events of even higher energies starting at 1015.2 eV. The focus will be on isolating the most penetrative showers as candidate gamma-ray showers occur deeper in the atmosphere. In this study, we test the hypothesis that the highest energy photons are coming from the disk of the Milky Way Galaxy by looking for enhancement of arrival directions of deep showers along the Galactic Plane. |
