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Polarization properties of Extragalactic Point Sources (EPS) at high frequencies

Polarization properties of Extragalactic Point Sources (EPS) at high frequencies. M. Massardi, J. Gonzalez-Nuevo & G. De Zotti Orsay, 27 October (2006). Existing observations of EPS polarization properties. Extrapolation to Higher Frequencies. Planck Reference Sky

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Polarization properties of Extragalactic Point Sources (EPS) at high frequencies

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  1. Polarization properties of Extragalactic Point Sources (EPS) at high frequencies M. Massardi, J. Gonzalez-Nuevo & G. De Zotti Orsay, 27 October (2006)

  2. Existing observations of EPS polarization properties

  3. Extrapolation to Higher Frequencies • Planck Reference Sky • Realistic all-sky simulations (background+foregrounds) at all the Planck channels: total intensity+polarization • Analytical method • Based on source number counts models and simple assumptions about the PS polarization properties.

  4. The Planck Reference-Sky: Point Sources (1) @ FIR Sources: IRAS sources combining Serjeant & Harrison (2005) and Clements compilation for Planck WG2. Proto-spheroidal galaxies (Granato et al. 2004 model & Gonzalez-Nuevo et al., 2005 software) Lensed Proto Spheroids (Perrotta et al., 2003) @ Radio Sources: Positions and 5GHz fluxes of real sources in 96% of cases (PMN, GB6, SUMSS, NVSS). Extrapolation of the Spectral behaviour using observed distributions (AT20G Pilot survey, WMAP, Fomalont et al. (1991))

  5. The Planck Reference-Sky: Point Sources (2) @ FIR Sources: Polarization Degree:1% Polarization Angle: Uniform random distribution @ Radio Sources: Polarization Degree: Random association according to Ricci et al. (2004) @ 18 GHz Polarization Angle: Uniform random distribution

  6. Analytical Method Following Tucci et al (2004)… De Zotti et al. (2005) Granato et al. (2004) … Source Number Counts Models • Simplest assumption: pn= 0.028 Independent variables Pol. Degree distribution

  7. l=100 200 mJy T/S=0.001 PS polarization power spectra for Bpol 5s (40mJy) 20’ T/S=0.1 • The minimum of the PS contamination at l=100 is reached at 143 GHz • New data at higher frequencies could modify this situation • PS contamination is almost negligible for l<300 (model & frequency dependence) • RefSky=Analytical method for <p2>=(0.028)2

  8. On-going observations: AT20G survey • AT20G is a 20 GHz survey (total intensity and polarization) of the southern sky (galactic & extragalactic sources) • Survey strategy (2.3’ primary beam @20GHz): • 8 GHz bandwidth analog correlator in 18-24 GHz • High scan rate (15 deg/min in declination) • 3 22m dishes ATCA antenna in EW configuration • Scanning along the meridian • In 2004-2005, 10000 sq deg with 4146 sources down to 50 mJy (-90<dec<-30) • In 2006 -30<dec<-15 almost 2000 new candidate sources

  9. On-going observations: AT20G survey median 2.6% mean 3.3±0.1% 1421 objects (2004 data) 853 upper limits 6 sources S>100 mJy

  10. On-going observations: AT20G survey • Follow ups: • @20 GHz to confirm positions, fluxes and polarization (mosaic) • 4.8, 8.6 & 100 GHz to study spectral behaviour, polarization, variability, HII regions, … • Polarization follow up (Oct 2006) at 18 GHz • 183 sources brighter than 500 mJy observed in 2004-2006 • 7 extended • 8 with polarized flux>100mJy • Median polarization degree (on pointlike sources) 2.9%

  11. On-going observations: AT20G survey 10.9 Jy of total intensity -> 1.4 Jy polarized integrated flux Core depolarized down to 5mJy

  12. Conclusions • Our knowledge about the radio source polarization properties is mainly based on data below 20 GHz. Practically we have no information for the IR sources. • Different methods to extrapolate the polarization properties agree to predict that the PS polarization contamination could play an important role in the B-mode observability. • New data (VLA, ATCA, APEX, ALMA, SKA, …) may introduce serious modification in our methods and, as a consequence, in our predictions.

  13. Polarization Power Spectrum Pol. Degree distribution Independent variables Source Number Counts Tucci et al., 2004

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