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Lower limits to the intracluster magnetic field are derived from modeling broad band X-ray spectra of 6 galaxy clusters with radio halos (A401, A754, A1367, Coma (A1656), A2256, and A2319). The 0.7 - 10 keV spectra for all clusters were obtained with the Advanced Satellite for Cosmology and Astrophysics (ASCA) Gas Imaging Spectrometer (GIS). For A401, A754, A1367, and A1656, data from the HEAO1-A2 High Energy Detector (HED) (2-60 keV) was included in a joint fit to further constrain the allowed non-thermal component. Upperlimits to the non-thermal X-ray emission are a factor of approximately 10 improvement over previous values. Lower limits to the average magnetic field derived from these upperlimits and the radio spectral parameters range from 0.08 - 0.30 microGauss. A seed intracluster field amplified by turbulence from galaxy motion through the intracluster medium should have an average value in the range of 0.1-0.2 (Goldman & Rephaeli, 1991; De Young, 1992), thus the lack of any detections makes it unlikely that field amplification is due to galaxy wakes. In addition, all of these clusters have an asymmetric surface brightness distribution while several also have X-ray spectroscopic evidence of a merger. We suggest that cluster mergers rather than galaxy wakes are the source of the magnetic field amplification.
Results are presented of a new VLA-ROSAT study that probes the magnetic field strength and distribution over a sample of 16 ``normal low redshift (z < 0.1) galaxy clusters. The clusters span two orders of magnitude in X-ray luminosity, and were selec
We find that the observed log N - log S relation of X-ray clusters can be reproduced remarkably well with a certain range of values for the fluctuation amplitude $sigma_8$ and the cosmological density parameter $Omega_0$ in cold dark matter (CDM) uni
We constrain anisotropic cosmic birefringence using four-point correlations of even-parity $E$-mode and odd-parity $B$-mode polarization in the cosmic microwave background measurements made by the POLARization of the Background Radiation (POLARBEAR)
We compute and investigate four types of imprint of a stochastic background of primordial magnetic fields (PMFs) on the cosmic microwave background (CMB) anisotropies: the impact of PMFs on the CMB spectra; the effect on CMB polarization induced by F
The origin of magnetic fields in the Universe is an open problem. Seed magnetic fields possibly produced in early times may have survived up to the present day close to their original form, providing an untapped window to the primeval Universe. The r