K. M. Huffenberger, D. Araujo, C. Bischoff, I. Buder, Y. Chinone, K. Cleary, A. Kusaka, R. Monsalve, S. K. Nss, L. B. Newburgh, R. Reeves, T. M. Ruud, I. K. Wehus, J. T.L. Zwart, C. Dickinson, H. K. Eriksen, T. Gaier, J. O. Gundersen, M. Hasegawa, M. HazumiA. D. Miller, S. J.E. Radford, A. C.S. Readhead, S. T. Staggs, O. Tajima, K. L. Thompson

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


We present polarization measurements of extragalactic radio sources observed during the cosmic microwave background polarization survey of the Q/U Imaging Experiment (QUIET), operating at 43 GHz (Q-band) and 95 GHz (W-band). We examine sources selected at 20 GHz from the public, >40 mJy catalog of the Australia Telescope (AT20G) survey. There are ∼480 such sources within QUIET's four low-foreground survey patches, including the nearby radio galaxies Centaurus A and Pictor A. The median error on our polarized flux density measurements is 30-40 mJy per Stokes parameter. At signal-to-noise ratio > 3 significance, we detect linear polarization for seven sources in Q-band and six in W-band; only 1.3 ± 1.1 detections per frequency band are expected by chance. For sources without a detection of polarized emission, we find that half of the sources have polarization amplitudes below 90 mJy (Q-band) and 106 mJy (W-band), at 95% confidence. Finally, we compare our polarization measurements to intensity and polarization measurements of the same sources from the literature. For the four sources with WMAP and Planck intensity measurements >1 Jy, the polarization fractions are above 1% in both QUIET bands. At high significance, we compute polarization fractions as much as 10%-20% for some sources, but the effects of source variability may cut that level in half for contemporaneous comparisons. Our results indicate that simple models - ones that scale a fixed polarization fraction with frequency - are inadequate to model the behavior of these sources and their contributions to polarization maps.

Original languageEnglish (US)
Article number112
JournalAstrophysical Journal
Issue number1
StatePublished - Jun 10 2015

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • cosmic background radiation
  • galaxies: active
  • galaxies: individual (Cen A, Pict A)
  • methods: statistical
  • polarizat


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