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S-PASS, a new view of the polarized sky Gianni Bernardi SKA SA On behalf of the S-PASS team

S-PASS, a new view of the polarized sky Gianni Bernardi SKA SA On behalf of the S-PASS team. CMB2013, Okinawa, June 10-14 th 2013. CMBleaks from CMB2013…. Thank you for the great conference!. Motivation 1: Polarized synchrotron emission is a foreground for CMB observations;

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S-PASS, a new view of the polarized sky Gianni Bernardi SKA SA On behalf of the S-PASS team

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  1. S-PASS, a new view of the polarized sky Gianni Bernardi SKA SA On behalf of the S-PASS team CMB2013, Okinawa, June 10-14th 2013

  2. CMBleaks from CMB2013… Thank you for the great conference!

  3. Motivation 1: Polarized synchrotron emission is a foreground for CMB observations; Motivation 2: Galactic science (particularly the magnetic field) Synchrotron polarized emission  magnetic field orientation (and strength) Synchrotron polarized emission at multiple frequencies  Faraday rotation  measurement of the magnetic field strength, orientation and direction parallel to the line of sight

  4. Motivation 2: Galactic science • 37543 extragalactic RMs (reprocessing of NVSS data, Taylor et al. 2009) simultaneously show large-scale coherence & small-scale fluctuations

  5. Predecessor: the Parkes Galactic Meridian Survey (PGMS) PI: E. Carretti • 5° degb-strip at l ~ 254°; • 2.3 GHz, 160 MHz bandwidth (2 MHz channels with high spectral isolation to reject RFI); • 9’ arcmin angular resolution; • 0.3 mK/pixel sensitivity (3’ pixel); • 0.3 on axis instrumental pol; • < 1% off axis instrumental pol; Carrettiet al., 2010

  6. Map-making • Cross scans and Emerson & Grave map-making technique of data at constant azimuth; • A quadratic fit to each elevation bin removes the ground pick up effectively • Disc region b > -20°, small scale structure; • Halo region b < -40°, lack of small scale structure, smooth emission;

  7. Foregrounds for CMB B-mode

  8. Evolution: the S-band Parkes All-Sky Survey (S-PASS) E. Carretti (PI), G. Bernardi. B.M. Gaensler. M. Haverkorn, M.Kesteven, S. Poppi. L. Staveley-Smith • To survey the polarized emission of the entire southern sky at 2.3 GHz • Dec < 0º (unshaded area); • Parkes: 2.3 GHz ; • 224 MHz BW (100+ ch); • FWHM = 9’; • sbeam < 1.0 mK; • 2000 h • 175 nights in 2.5 yrs • Started 07, completed in 2010 • Goals: synchrotron emission, Galactic magnetic field, CMB foregrounds

  9. The 1.4 GHz scenario • All sky maps at 1.4 GHz, FWHM  36’; • Single channel surveys: no RM measures; • Galactic Disc strongly depolarized |b| < 30°  call for higher frequency (depolarization is frequency dependent) depolarization

  10. Mapping: fast (120°/8 min), extended AZ scans (minimize ground pick up and 1/f noise) • small area basket weaving: not an option for S-PASS • ground emission contamination (EL dependant) • high speed requires significant overhead for short scans (10o-20o) • short scans: mean emission on area scale is lost • New exotic/non-standard scanning strategies has been developed for S-PASS • AZ scans • Long AZ scans at South Pole EL to cover all Dec in one haul (~115o) • uses the Sky rotation to observe all RA 24 hrs. • each day/night a zig-zag track is observed in the sky • one zig-zag per night: accurate start timing is required

  11. Results: total & polarized intensity

  12. Results: Stokes Q

  13. Results: Stokes U

  14. WMAP & S-PASS Page et al. (2003) model

  15. WMAP & S-PASS 23 GHz 2.3 GHz

  16. Giant Magnetized Outflows from the Centre of the Milky Way Northern Lobe Southern Lobe Carrettiet al., 2013

  17. Conclusions • Synchrotron polarization is a unique probe of the ISM, particularly of the Galactic magnetic field and the density of the thermal gas. It is also a relevant contaminant for CMB polarization observations on large scales, particularly looking for the CMB B-mode; • We have completed a 2.3 GHz polarization survey of the southern sky with 9’ resolution. The survey has SNR > 5 (9’ arcmin beam) over 96% of the observed sky; • We “stumbled upon” two giant polarized plumes connected with the Galactic Centre  they morphologically match the γ-ray bubbles – and the extended Planck haze. The plumes/haze/bubbles can be explained as the result of massive star formation at the Galactic Centre – but it might not be the end of the story; • Several ongoing activities: foreground estimates in low emission regions, comparison with the 1.4 GHz and 23 GHz data, analysis of bright regions (Gum nebula), point source RM; • We aim at a near future data release (~2 months?); people could use it to estimate foreground contamination in the CMB data a/o include them in their foreground subtraction process (the high latitude emission does not seem to be affected by Faraday rotation – wee next C-BASS talk for more on this); THANK YOU

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