Gaurang B. Yodh

Professor, Physics & Astronomy
School of Physical Sciences

PH.D., University of Chicago, 1955

M.S.,, University of Chicago, 1951

B.S., University of Bombay, 1948, Physics

Phone: (949) 824-6660
Fax: (949) 824-2174

University of California, Irvine
3162 Frederick Reines Hall
Previously PS2
Mail Code: 4575
Irvine, CA 92697
Research Interests
High Energy Astro-Particle Physics and Cosmic Rays, Elementary Particle Physics
Academic Distinctions
Fellow American Physical Society, Fellow American Association of Advancement of Science, Fellow of the Institute of Physics in UK,Chancellors Distinguished
Scholar and Teacher, Univ of Maryland, 1981, Outstanding Research in Physics Award of the American Chapter of Indian Physicsists in America
Research Abstract
My current research is directed towards studying astrophysical sources by techniques of very high energy gamma ray and neutrino emission which probe some of the most extreme environments in the known universe. These environments are to be found in sources which can accelerate particles to very high energies, such as Supernova remenants and plerions in our own galaxy, active galactic nuclei(AGNs) and Gamma Ray Bursts(GRBs) outside our galaxy extending out to cosmological distances and evaporating primordial black holes (PBHs) in our neighbourhood. Other sources are extended, such as TeV emission from the galactic plane due to cosmic ray interactions with the interstellar medium and ultra high energy neutrino emission from interactions of extremely high energy cosmic rays with the cosmic microwave background. This research is being done by three different instruments – telescopes: Milagro, AMANDA II and ANITA. Very high energy gamma rays and neutrinos form symbiotically connected species, emitted in the sources from collision of high energy paricles with ambient matter or ambient photons in the source.

Very high energy gamma rays are being searched for with the Milagro experiment, located at high altitude in the Jemez mountains in New Mexico. This is a water Cherenkov detector which records the showers produced by TeV gamma rays in the atmosphere using some 800 photo-multipliers to capture the light emitted by shower particles as they enter a pond containing 5 million tons of optically clear water. The pond has a size of about two football fields, or 5000 square meters ! It operates continously, scans the overhead sky for very high energy gamma rays and can record both steady and transient events in the universe. We can study " bursts " covering time scales from a milli second to steady state. We can alert telescopes in other wavelength regions with 4 seconds of the occurrence of a burst. We have seen three sources, one galactic the Crab nebula and two extragalactic sources- AGN Mrk 421 and Mrk501 during the last few years. We have also made the first signficant detection of TeV gamma rays from the galactic plane - expected from cosmic ray interactions.

Very high energy neutrinos are being searched for with the AMANDA II detector located in deep ice at the South Pole. This instrument, the first one of its kind, detects neutrinos coming upwards through the ice (which removes all other particles) by the Cherenkov light they emit in the antarctic ice which is exceptionally clear at great depths. Although the telescope has not detected any astrophysical sources, we have put signifcant upper limts to the flux of astrophysical neutrinos to restrict current theoretical models. The telescope also monitors for Supernova explosions if they go off somewhere in our galaxy.

ANITA is a totally new balloon borne telescope, which is designed to detect radio signals from showers produced by extremely high energy neutrinos skimming the ice . The telescope has a very large acceptance so as to be able detect the small predicted neutrino flux from the interaction of ultra high energy cosmic rays with the cosmic microwave background. The instrument had a successful first flight around the antarctic continent and the full experiment is supposed to be flown in 2006.

I teach both undergraduate and graduate courses in Physics and Astronomy. My courses include high energy astrophysics, elementary particle physics, classical mechanics, conceptual physics, how things work,advanced and elementary laboratories.
Constraints on Very High Energy Gamma-Ray Emission from Gamma-Ray Bursts R. Atkins et al Astrophysical Journal 630 (2005) 996-1002
Evidence for TeV Gamma-Ray Emission from a Region of the Galactic Plane R. Atkins et al.Physical Review Letters 95 (2005) 251103
Discovery of TeV Gamma-Ray Emission from the Cygnus Region of the Galaxy A. A. Abdo et al.Astrophysical Journal Letters 658 (2007) L33-L36
TeV Gamma-Ray Sources from a Survey of the Galactic Plane with Milagro A. A. Abdo et al.Astrophysical Journal Letters 664 (2007) L91-L94
Milagro Constraints on Very High Energy Emission from Short-Duration Gamma-Ray Bursts, A. A. Abdo et al.Astrophysical Journal 666 (2007) 361-367
NSF Grant: Astrophysics with Milagro, 2003-2006
Professional Societies
Member, Division of Particle and Fields of American Physical
Member, Division of Astrophysics of American Physical Societ
Member, American Association of the Advancement of Science.
Member, American Astronomical Society
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