Detection thresholds and bias correction in polarized intensity
Abstract
Detection thresholds in polarized intensity and polarization bias correction are investigated for surveys where the polarization information is obtained from rotation measure (RM) synthesis. Considering unresolved sources with a single RM, a detection threshold of 8QU applied to the Faraday spectrum will retrieve the RM with a false detection rate less than 10-4, but polarized intensity is more strongly biased than Ricean statistics suggest. For a detection threshold of 5QU, the false detection rate increases to ∼4%, depending also on 2 coverage and the extent of the Faraday spectrum. Non-Gaussian noise in Stokes Q and U due to imperfect imaging and calibration can be represented by a distribution that is the sum of a Gaussian and an exponential. The non-Gaussian wings of the noise distribution increase the false detection rate in polarized intensity by orders of magnitude. Monte Carlo simulations assuming non-Gaussian noise in Q and U give false detection rates at 8QU similar to Ricean false detection rates at 4.9QU. Journal compilation © Australian Mammal Society 2012.
Publication Title
Publications of the Astronomical Society of Australia
Recommended Citation
George, S., Stil, J., & Keller, B. (2012). Detection thresholds and bias correction in polarized intensity. Publications of the Astronomical Society of Australia, 29 (3), 214-220. https://doi.org/10.1071/AS11027
