Faraday Rotation Search for Magnetic Fields in Nearby Large Scale Structure
Abstract
A new, large sample of extraglactic radio source Faraday rotation measures (RM) are compared with local large scale structure (LSS) using an analysis of galaxy distributions from the CfA2 and 2MASS catalogs. 3 nearby supercluster zones were examined, the Virgo, Hercules, and Perseus-Pisces superclusters. The selection of the RM's was optimized to minimize ``pollution'' due to galaxy clusters and other RM contributions that are unlikely to be related to local LSS.
Two different analysis methods were applied to the optical galaxy catalogs: For 2MASS, smoothed galaxy column densities were calculated for a magnitude-limited subset, and compared with smoothed RM's (SRM) at the same resolution. For CfA2, the spectroscopic redshifts made it possible to compute 3-D supercluster volumes and estimate a weighted pathlength for each RM intersection through the computed volume of galaxy-overdense filaments. Both methods showed a tentative correlation with SRM for the Perseus-Pisces supercluster. A positive SRM--supercluster volume correlation, less tight, was found for the Hercules supercluster. The Virgo supercluster galaxies were too ``dilute'', and covered too much sky angle to give a result. For the P-P and Hercules superclusters we obtain an upper limit for LSS filament magnetic fields of ∼ 0.3 μ G, normalized to a 500 kpc pathlength. This is interestingly close to recent theoretical estimates. There is tentative evidence that we have actually detected fields near this level in the IGM of the P-P supercluster galaxy overdensity zones. (to be published in ApJ, Jan 20 issue, 2006) We acknowledge support from the DOE through an LDRD grant at LANL, and from the Natural Sciences and Engineering Research Council of Canada (NSERC).- Publication:
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American Astronomical Society Meeting Abstracts #207
- Pub Date:
- June 2006
- Bibcode:
- 2006AAS...20720814K