35 research outputs found
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
A Demonstration of AMSU Retrieval Precision for Mean Upper Tropospheric Humidity by a Non-Linear Multi-Channel Regression Method
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
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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