This award provides continued support for this particle astrophysics group to participate in the operation and analysis of data from the Very Energetic Radiation-Imaging Telescope Array System (VERITAS). VERITAS is an array of four 12-m Cherenkov telescopes which use the imaging atmospheric Cherenkov technique to detect and characterize the flux of ~50 GeV to ~50 TeV photons from astrophysical sources. The VERITAS array has successfully operated for two years at its new permanent site at the Whipple Observatory basecamp and has already detected or discovered 21 sources of very-high-energy gamma-rays, including M82, the prototypical starburst galaxy whose detection by VERITAS this year represents the discovery of an entirely new class of gamma-ray emitter.
The University of Chicago group has been a key participant in the VERITAS project since its inception. From design and construction to commissioning and operation and now to analysis and interpretation, Chicago has assumed leadership roles in all aspects of VERITAS. This award will allow the group to continue in this capacity.
In the area of Broader Impacts, the field of TeV astronomy has impacts on many other fields of science, from the study of the high-energy particle acceleration to fundamental physics questions such as the nature of Dark Matter. The VERITAS project has always had a strong involvement of both graduate and undergraduate students. The telescope relocation this summer was accomplished in large part by undergraduate summer students. While much of the VERITAS outreach activity is concentrated at the Smithsonian facility at the telescope site, there is also a strong local effort. At Chicago, they continue to profit from a successful partnership with Adler Planetarium for producing public lectures and classes for high school teachers. Members of the VERITAS group frequently participate in these efforts.
This project's primary focus was to support the University of Chicago group's participation in the VERITAS experiment. VERITAS is an array of four 12-meter Cherenkov telescopes located in southern Arizona which are designed to use the atmospheric Cherenkov technique to measure very-high-energy gamma rays from astrophysical sourecs. VHE Astrophysics, as a field, focuses on exploring the most violent and energetic objects in the Galaxy and Universe, through the gamma radiation produced in those objects. This field was invented in the United States, and VERITAS represents the second-generation instrument designed for carrying out this type of research. Over the past 4 years, our research team has had considerable impact on the entire world of high-energy astronomy through the publication of 70+ scientific papers and proceedings. This body of work includes the discovery of gamma-ray emission from several new sources in the sky, including several remnants of Galactic supernova explosions, the super-massive black holes at the centers of other galaxies, and an entirely new class of TeV-emitter, the starburst galaxy. These results have helped improve our understanding of particle acceleration processes in extreme environments. A particularly intriguing result, published in the journal Science, was the detection of pulsed gamma-ray emission from the Crab pulsar, an unexpected result not explained by any current pulsar model. The University of Chicago group has been a key participant in the VERITAS project throughout this work, and has assumed important roles in all aspects of the project, from design and construction to commissioning and operation and now to analysis and interpretation. The current grant has allowed us to maintain this commitment. An important aspect of our work has been the training of future scientists through the strong involvement of both graduate and undergraduate students in research activities. Since 2009, over 15 graduate students have received PhD's at US institutions working on gamma-ray science related to the VERITAS instrument, including three from the University of Chicago. These young scientists will be the teachers and front-line researchers of the next generation of US Science, and providing them with a training ground is of the utmost importance. Indeed, over the past grant period, three former members of our research group have accepted faculty positions at US Universities. The impacts of our work over and above this include important consequences for other fields of science. Most notably, our limits on gamma-ray emission from Dwarf Spheroidal Galaxies have implications for the nature and distribution of dark matter in the Universe. Likewise, our measurement of gamma rays from the galaxy M82 has contributed to a better understanding of cosmic radiation, a flux of extra-terrestrial relativistic particles discovered over 100 years ago, the origin of which remains unknown.
