Milano Polarimeter (MIPOL) Data Product


Radiometer properties

MIPOL sensitivity, gain stability, correlator offsets
Type Quantity Circular Polariz. Linear Polariz. Unit
Total power Sensitivity ch. 1 1165.8±20.0 1220.3±20.8 adu/K
  Sensitivity ch. 2 1474.0±25.4 1457.8±23.9 adu/K
  Stability ch. 1 8.0 10-9 4.3 10-9 s-1
  Stability ch.2 6.4 10-9 4.4 10-9 s-1
         
Correlator Sensitivity ch. 1 (2.9±0.9) 105 (3.0±0.9) 105 adu/K
  Sensitivity ch. 2 (2.9±0.9) 105 (3.0±0.9) 105 adu/K
Offset ch. 1 -(0.36±0.04) 105 (1.85±0.07) 105 adu
  Offset ch. 2 -(1.79±0.08) 105 -(1.06±0.06) 105 adu
  Stability ch. 1 4.3 10-9 4.0 10-9 s-1
  Stability ch. 2 4.4 10-9 8.5 10-9 s-1


Observations of CMB in Circular Polarization mode

  • Site : Testa Grigia Observatory
  • Between Nov. 10th and Dec. 9th 2009 observation in circular polarization mode followed (Dec.17th 2009 – Jan. 20th 2010) by tests of the system performance in linear polarization mode.
  • Half Power Beam Width: 7°, system time constant: 6 s, sampling of the system outputs: every 2 s
  • Continuous drift scans, while the radiometer beam moved at a constant pace along the meridian from declination δin=(41.1±0.1)
    to δfin=(15.8±0.1) in 300 s, went back to δin in 18 s then the cycle was repeated.
  • Data collected at night time (1 hour after sunset - 1 hour before sunrise) with clear sky were arranged in (2o x 2o) pixels of a (α, δ) map
  • Resulting map covers almost uniformly the sky region (-30o ≤ α ≤ +165o, 15o N ≤ δ ≤ 41o N)

Summary of results
An improved upper limit to the CMB circular polarization
at large angular scales
Mainini R. et al. (2013) JCAP, 08, 033, arXiv: 1307.6090v2, ADS


Atmospheric and system temperatures from Total Power measurements with the horn aimed at the zenith
  Linear mode
full sample		 Circular mode
full sample		 Circular mode
sub sample(o)		 Unit
Tch1atm 9.55±0.21 7.91±0.04 8.45±0.04 K
Tch2atm 7.25±0.26 8.70±0.05 9.49±0.06 K
Tch1sys 83.6±1.4 82.9±1.4 75.36±0.05 K
Tch2sys 89.7±1.5 84.1±1.5 76.05±0.07 K

(o) data collected between Julian days 40136 and 40137 when the observing conditions were particularly good


  • contribution of atmospheric and ground emission to the correlator outputs
    with the horn aimed at the zenith

    • tan (χatm) = – (1.68±0.09)  Tatm = (0.087±0.002) K
    tan (χgr) = - (0.24±0.06)  Tgr = (0.006±0.046) K

Mean <V> , standard deviation σV, average rms per pixel σVpix, average standard
deviation of the mean per pixel σ<V>pix of V, the circular polarization Stokes parameter
Pixel size Number of pixels <V> σV σVpix σ<V>pix Unit
2° x 2° unbinned data 518 -(0.02±0.06) 1.29 -- -- mK
8° x 8° 64 -(0.02±0.08) 0.64 1.14 0.43 mK
12° x 12° 32 -(0.02±0.07) 0.38 1.27 0.35 mK
24° x 24° 9 -(0.02±0.06) 0.15 1.37 0.21 mK


Test for the gaussianity of the data
Pixel size f μ=<V>     σ=σV
χ2    P		 Best fit
χ2    P		 Simulations
χ2    P
8° x 8° 5 6.04    0.70 3.90    0.44 9.95    0.92
12° x 12° 1 1.96    0.76 0.79    0.55 2.81    0.83
2° x 2° 55 46.60    0.20 -- --

f = degree of freedom, P = probability of the assumed Gaussian model



Upper limits to the degree of circular polarization of the CMB by classical, Bayesian and spherical harmonics analysis methods
Method Classical Bayesian Spherical harmonics
Pixel size ΠVCMB ΠVCMB ΠVCMB
8° x 8° 5.0 10-4 4.0 10-4 4.3 10-4
<θ>=7.5°
12° x 12° 2.7 10-4 3.2 10-4 2.4 10-4
<θ>=10.6°
24° x 24° 0.7 10-4 2.1 10-4 2.7 10-4
<θ>=18.0°

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