Experimental Astrophysics with the STACEE and Pierre Auger Observatories

Case Western Reserve University, Cleveland OH

Investigators

Abstract

This proposal requests support for the research activities of the High Energy Astrophysics (HEA) group in the Physics Department at Case Western Reserve University which is active in two major experimental projects: (1) The Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE) for detecting gamma-rays in the 50 to 250 GeV range, and (2) The Pierre Auger Observatory (PAO) for observing the highest energy cosmic rays at EeV energies. STACEE is a ground-based gamma-ray detector using the heliostat mirrors of a solar array to collect atmospheric Cherenkov radiation. The large mirror area available at the array permits STACEE to operate at energies well below previous ground-based instruments and to explore the gamma-ray energy range between 50 and 250 GeV. The experiment has been in continuous operation since 2001 and has observed and reported results on several Active Galactic Nuclei (AGN), gamma-ray pulsars and supernova remnants, and has searched for high-energy emission from Gamma-Ray Bursters (GRB). This proposal requests support for the continued operation of STACEE, and the participation of the Case HEA group as one of its founding members. Activities on STACEE will ramp down during the proposal period as this experiment ceases observations on June 1, 2007. The Auger Observatory is a new major international experiment to measure the energy and arrival direction of Ultra High Energy Cosmic Rays (UHECR) above 1020 eV. The origin of the UHECR remains one of the important questions being probed in UHECR physics. The Auger Observatory is a hybrid detector consisting of two co-located detector systems: (1) an array of 1,600 water Cherenkov Surface Detector (SD) stations spread over 3,000 square kilometers area for detecting air shower particles on the ground, and (2) a set of four Fluorescence Detector (FD) telescopes which provide stereo calorimetric measurements of the development of cosmic ray showers as the propagate through the atmosphere. The experiment is located near Malargue, Argentina and construction is well underway, with three of the four FD's operational and more than 950 of the 1,600 SD stations installed and running. Data from the partially complete Auger observatory are being collected and the first set of science results from Auger have recently been presented. The Auger Observatory will be completed by early 2007. This proposal requests support for the continued participation of the Case group in Auger, which participates in several areas of detector development, deployment, calibration and data analysis. Broader impacts: Several members of the Case group are active in a variety of education and outreach programs, including a new program for physical science instruction for Cleveland high school teachers and the application of wireless transmitters ("clickers") for introductory physics education. Several techniques developed for STACEE and Auger by the Case group are applicable in other arenas, including: (1) the use of heliostats to support remote sensing by earth-viewing satellites, (2) the design and application of new types of non-imaging optical systems, and (3) the development of mirror measurement techniques for solar energy applications.