Detection Thresholds and Bias Correction in Polarized Intensity

Дата и время публикации : 2011-06-27T11:09:32Z

Авторы публикации и институты :
Samuel J. George
Jeroen M. Stil
Ben W. Keller

Ссылка на журнал-издание: Ссылка на журнал-издание не найдена
Коментарии к cтатье: 8 pages, 8 figures, accepted for publication in Publications of the Astronomical Society of Australia
Первичная категория: astro-ph.IM

Все категории : astro-ph.IM, astro-ph.CO

Краткий обзор статьи: Detection thresholds in polarized intensity and polarization bias correction are investigated for surveys where the polarization information is obtained from RM synthesis. Considering unresolved sources with a single rotation measure, a detection threshold of $8 sigma_{QU}$ 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 $5 sigma_{QU}$, the false detection rate increases to ~4%, depending also on $lambda^2$ 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 $8 sigma_{QU}$ similar to Ricean false detection rates at $4.9 sigma_{QU}$.

Category: Physics