SEVEN-YEAR WILKINSON MICROWAVE ANISOTROPY PROBE (WMAP) OBSERVATIONS: PLANETS AND CELESTIAL CALIBRATION SOURCES

By J. Weiland, N. Odegard, R. Hill, Edward J. Wollack, Gary F. Hinshaw, M. Greason, N. Jarosik, L. Page, C. Bennett, J. Dunkley and 22 more. 2010

185 citations recorded by the source corpus.

We present WMAP seven-year observations of bright sources which are often used as calibrators at microwave frequencies. Ten objects are studied in five frequency bands (23–94 GHz): the outer planets (Mars, Jupiter, Saturn, Uranus, and Neptune) and five fixed celestial sources (Cas A, Tau A, Cyg A, 3C274, and 3C58). The seven-year analysis of Jupiter provides temperatures which are within 1σ of the previously published WMAP five-year values, with slightly tighter constraints on variability with orbital phase (0.2% ± 0.4%), and limits (but no detections) on linear polarization. Observed temperatures for both Mars and Saturn vary significantly with viewing geometry. Scaling factors are provided which, when multiplied by the Wright Mars thermal model predictions at 350 μm, reproduce WMAP seasonally averaged observations of Mars within ∼2%. An empirical model is described which fits brightness variations of Saturn due to geometrical effects and can be used to predict the WMAP observations to within 3%. Seven-year mean temperatures for Uranus and Neptune are also tabulated. Uncertainties in Uranus temperatures are 3%–4% in the 41, 61, and 94 GHz bands; the smallest uncertainty for Neptune is 8% for the 94 GHz band. Intriguingly, the spectrum of Uranus appears to show a dip at ∼30 GHz of unidentified origin, although the feature is not of high statistical significance. Flux densities for the five selected fixed celestial sources are derived from the seven-year WMAP sky maps and are tabulated for Stokes I, Q, and U, along with polarization fraction and position angle. Fractional uncertainties for the Stokes I fluxes are typically 1% to 3%. Source variability over the seven-year baseline is also estimated. Significant secular decrease is seen for Cas A and Tau A: our results are consistent with a frequency-independent decrease of about 0.53% per year for Cas A and 0.22% per year for Tau A. We present WMAP polarization data with uncertainties of a few percent for Tau A. Where appropriate, WMAP results are compared against previous findings in the literature. With an absolute calibration uncertainty of 0.2%, WMAP data are a valuable asset for calibration work.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/d6ed230390ead42a22477a906aa5449156c1ac7e

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Citations in the corpus

NINE-YEAR WILKINSON MICROWAVE ANISOTROPY PROBE (WMAP) OBSERVATIONS: FINAL MAPS AND RESULTS (2012, methodology): “The geometrical ring boundaries and relative ratios τ0,i/τ0,max are constrained as per Table 10 of Weiland et al. (2011), where τ0,max is the ring-normal optical depth for the most optically thick ring (ring 3, i.e. the outer B ring).”
AN ACCURATE FLUX DENSITY SCALE FROM 1 TO 50 GHz (2012, methodology): “The WMAP brightness temperatures of Mars published in Weiland et al. (2011) are given in terms of the “Rayleigh–Jeans” brightness temperature, defined as TRJ = λ 2Sν 2kΩ , (6) and have not been adjusted by the blockage of the sky background.”
Planck2015 results: XXVI. The SecondPlanckCatalogue of Compact Sources (2015, unknown): “24, where we compare the polarization position angles from WMAP and IRAM with the new measurements from Planck.”
A MEASUREMENT OF THE COSMIC MICROWAVE BACKGROUND B-MODE POLARIZATION POWER SPECTRUM AT SUB-DEGREE SCALES WITH POLARBEAR (2014, methodology): “Note that this measured polarization efficiency is strongly affected by any difference in polarization fraction between 90 and 148 GHz.”