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A Clash of Clusters Provides New Clue to Dark Matter
Special ACKS Seminar: Dragan Huterer
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ACKS Seminar: Trixi Wunderer (Berkeley SSL)
| What | seminar ACKS |
|---|---|
| When |
15 February 07 from 04:00 pm to 05:30 pm |
| Where | Campus: Phys & Astro Bldg 1st fl conf rm (102/103) |
| Contact Name | Roger Blandford |
| Contact Email | rdb3@stanford.edu |
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The MeV view of the Gamma-Ray Sky
Abstract
MeV gamma-ray astronomy provides access to a part of the electromagnetic spectrum that carries unique information: it encompasses the regime of nuclear binding energies, as well as the electron/positron rest mass. It is also in this energy regime that the most violent explosions, Gamma-Ray Bursts, exhibit the peak of their emission. Observations of gamma-ray lines constrain the abundance and kinematics of individual isotopes from supernovae, novae, and stellar winds - thus teaching us about nucleosynthesis processes that are part of the cycle of matter in our universe. At the same time, observations of these isotopes, combined with stellar evolution models, constrain the current star formation rate in our galaxy. MeV observations of Gamma-Ray Bursts reveal flares of sub-second durations; these extremely short emission timescales, combined with their cosmological distances and emission up to MeV energies and beyond, make GRB observations a promising means to constraining possible violations of Lorentz Invariance, and thus possibly the Quantum Gravity energy scale.
Today, GRB flare photons are detected only up to ~15 MeV - a situation that will drastically change with the launch of GLAST. Similarly, while current instrumentation allows us glimpses of some nucleosynthesis processes, many aspects cannot be addressed due to lack of sensitivity and/or angular resolution. The next-generation Compton telescope (ACT) will provide a high-sensitivity all-sky MeV survey. MeV gamma-ray astronomy beyond ACT will have to rely on gamma-ray lenses - and the European 'Gamma Ray Imager' may pioneer that approach.
Stanford High Performance Computing Conference IV