| Autor: |
K. M. Huffenberger, D. Araujo, C. Bischoff, I. Buder, Y. Chinone, K. Cleary, A. Kusaka, R. Monsalve, S. K. Næss, 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. Hazumi |
| Předmět: |
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| Zdroj: |
Astrophysical Journal; 6/10/2015, Vol. 806 Issue 1, p1-1, 1p |
| Abstrakt: |
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. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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