Fermi Large Area Telescope Constraints on the Gamma-ray Opacity of the Universe

The Extragalactic Background Light (EBL) includes photons with wavelengths from ultraviolet to infrared, which are effective at attenuating gamma rays with energy above ~10 GeV during propagation from sources at cosmological distances. This results in a redshift- and energy-dependent attenuation of the gamma-ray flux of extragalactic sources such as blazars and Gamma-Ray Bursts (GRBs). The Large Area Telescope onboard Fermi detects a sample of gamma-ray blazars with redshift up to z~3, and GRBs with redshift up to z~4.3. Using photons above 10 GeV collected by Fermi over more than one year of observations for these sources, we investigate the effect of gamma-ray flux attenuation by the EBL. We place upper limits on the gamma-ray opacity of the Universe at various energies and redshifts, and compare this with predictions from well-known EBL models. We find that an EBL intensity in the optical-ultraviolet wavelengths as great as predicted by the "baseline" model of Stecker et al. (2006) can be ruled out with high confidence.Comment: 42 pages, 12 figures, accepted version (24 Aug.2010) for publication in ApJ; Contact authors: A. Bouvier, A. Chen, S. Raino, S. Razzaque, A. Reimer, L.C. Reye

4. Title and Subtitle Technical Noise Supplement to the Caltrans Traffic Noise Analysis Protocol A Guide for the Measuring, Modeling, and Abating Highway Operation and Construction Noise Impacts

This document updates and supersedes th

Nanostructure of collagen fibrils in human nucleus pulposus and its correlation with macroscale tissue mechanics

10.1002/jor.21010Journal of Orthopaedic Research284497-502JORE

Site Environmental Report for 2022

The annual Site Environmental Report documents Lawrence Berkeley National Laboratory’s performance in reducing its environmental impacts, progress toward cleaning up groundwater contamination, and compliance with applicable Department of Energy, federal, state, and local environmental regulations

Site Environmental Report for 2021

The annual Site Environmental Report documents Lawrence Berkeley National Laboratory’s performance in reducing its environmental impacts, progress toward cleaning up groundwater contamination, and compliance with applicable Department of Energy, federal, state, and local environmental regulations