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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.

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Presentation on theme: "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."— Presentation transcript:

1 S-PASS, a new view of the polarized sky Gianni Bernardi SKA SA On behalf of the S-PASS team CMB2013, Okinawa, June th 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 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° deg b-strip at l ~ 254°; 5° deg b-strip at l ~ 254°; 2.3 GHz, 160 MHz bandwidth (2 MHz channels with high spectral isolation to reject RFI); 2.3 GHz, 160 MHz bandwidth (2 MHz channels with high spectral isolation to reject RFI); 9’ arcmin angular resolution; 9’ arcmin angular resolution; 0.3 mK/pixel sensitivity (3’ pixel); 0.3 mK/pixel sensitivity (3’ pixel); 0.3 on axis instrumental pol; 0.3 on axis instrumental pol; < 1% off axis instrumental pol; < 1% off axis instrumental pol; Carretti et al., 2010

6 Map-making Cross scans and Emerson & Grave map-making technique of data at constant azimuth; 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 A quadratic fit to each elevation bin removes the ground pick up effectively Disc region b > -20°, small scale structure; Disc region b > -20°, small scale structure; Halo region b < -40°, lack of small scale structure, smooth emission; 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 GHzTo 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’; – s beam < 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 depolarization All sky maps at 1.4 GHz, FWHM  36’; All sky maps at 1.4 GHz, FWHM  36’; Single channel surveys: no RM measures; Single channel surveys: no RM measures; Galactic Disc strongly depolarized |b| < 30°  call for higher frequency (depolarization is frequency dependent) Galactic Disc strongly depolarized |b| < 30°  call for higher frequency (depolarization is frequency dependent) The 1.4 GHz scenario

10 small area basket weaving: not an option for S-PASS small area basket weaving: not an option for S-PASS – ground emission contamination (EL dependant) – high speed requires significant overhead for short scans (10 o -20 o ) – short scans: mean emission on area scale is lost New exotic/non-standard scanning strategies has been developed for S-PASS 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 (~115 o ) – 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 Mapping: fast (120°/8 min), extended AZ scans (minimize ground pick up and 1/f noise)

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 Northern Lobe Southern Lobe Giant Magnetized Outflows from the Centre of the Milky Way Carretti et 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; 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 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; 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; 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); 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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