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Title: Degree of polarization and source counts of faint radio sources from Stacking Polarized intensity

We present stacking polarized intensity as a means to study the polarization of sources that are too faint to be detected individually in surveys of polarized radio sources. Stacking offers not only high sensitivity to the median signal of a class of radio sources, but also avoids a detection threshold in polarized intensity, and therefore an arbitrary exclusion of sources with a low percentage of polarization. Correction for polarization bias is done through a Monte Carlo analysis and tested on a simulated survey. We show that the nonlinear relation between the real polarized signal and the detected signal requires knowledge of the shape of the distribution of fractional polarization, which we constrain using the ratio of the upper quartile to the lower quartile of the distribution of stacked polarized intensities. Stacking polarized intensity for NRAO VLA Sky Survey (NVSS) sources down to the detection limit in Stokes I, we find a gradual increase in median fractional polarization that is consistent with a trend that was noticed before for bright NVSS sources, but is much more gradual than found by previous deep surveys of radio polarization. Consequently, the polarized radio source counts derived from our stacking experiment predict fewer polarized radiomore » sources for future surveys with the Square Kilometre Array and its pathfinders.« less
Authors:
;  [1] ;  [2] ;  [3]
  1. Department of Physics and Astronomy, University of Calgary, 2500 University Drive NW, Calgary AB, T2N 1N4 (Canada)
  2. Department of Physics and Astronomy, McMaster University, 1280 Main Street W, Hamilton ON, L8S 4M1 (Canada)
  3. Department of Astronomy, University of Cape Town and Physics Department, University of Western Cape, Private Bag X3, Rondebosch 7701, Republic of South Africa (South Africa)
Publication Date:
OSTI Identifier:
22356804
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 787; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CORRECTIONS; DATA ANALYSIS; DETECTION; DISTRIBUTION; GALAXIES; MAGNETIC FIELDS; MONTE CARLO METHOD; NONLINEAR PROBLEMS; POLARIZATION; SENSITIVITY; SIMULATION; SKY