Galactic radioemission a problem for precision cosmology
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Absolute Temperatures at Short CM-Waves with a Lunar Radio Telescope. Galactic Radioemission – a problem for precision cosmology ?. Wolfgang Reich Max-Planck-Institut für Radioastronomie Bonn. Bremen 22./23.3.2005. Summary and Conclusion.

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Galactic radioemission a problem for precision cosmology

Galactic Radioemission – a problem for precision cosmology ?

Wolfgang Reich

Max-Planck-Institut für Radioastronomie

Bonn

Bremen 22./23.3.2005


Summary and conclusion
Summary and Conclusion

  • Scientific needs: absolutely calibrated sky surveys in I and PI between ~5-15 GHz

  • Technical needs: 10m/15m meridian telescope operating at 3-5 frequencies

  • Location: backside of the moon close to equator (+/- ~5° latitude)


Absolutely Calibrated All-Sky Radio Continuum Surveys408 MHzHaslam et al. HPBW = 51’,  T = 2K1420 MHzReich et al. HPBW = 35’,  T= 50mKSpectral Index ß 408 MHz / 1420 MHz = 2.4 (blue) – 3.0 (red)Reich et al.

ß


Galactic emission
Galactic emission

  • mixture of synchrotron ß = 2.4…3.2 + thermal emission ß = 2.1

  • anomalous dust: 10 GHz – 30 GHz ?

  • component separation difficult

  • absolutely calibrated surveys at several frequencies needed

  • extrapolation to CMB-Frequencies uncertain


Absolute calibration sequence for total intensities
Absolute Calibration Sequence for Total Intensities

  • Absolute skyhorn measurements ~10°/15° angular resolution

     calibration of medium angular resolution all-sky surveys

     calibration of high resolution maps e.g. Galactic plane surveys



anomalous dust

Available surveys


+212 µK


1 41 ghz dwingeloo polarization survey brouw spoelstra 1976 absolutely calibrated
1.41 GHz Dwingeloo polarization surveyBrouw & Spoelstra, 1976absolutely calibrated


Anticorrelation of i pi with galactic latitude reich et al 1990 duncan et al 1999
Anticorrelation of I/ PI with Galactic latitude (Reich et al. 1990, Duncan et al. 1999)


24 x 9 section centered at l b 162 0 1 4 ghz effelsberg medium latitude survey emls
24° x 9° section centered at l , b = 162°,0° 1.4 GHz Effelsberg Medium Latitude Survey (EMLS)

I

PI


Absolute polarization calibration a must for galactic emission
Absolute Polarization Calibration: „A Must“ for Galactic Emission

  • Vector addition for polarisation scalar addition for total intensity

  • PI = (U2 + Q2)1/2 measured

  • Φ = 0.5 atan (U/Q)

  • PIabsolute = ((U+Uoff)2 +(Q+Qoff)2)1/2

  • Φ = 0.5 atan (U+Uoff)/(Q+Qoff)

    U/Q may be positive or negative


Rotation measure rm rad m 2 rm 0 81 n e cm 3 b g l pc rad rm 2 m
Rotation Measure: RM [rad/m2] RM = 0.81 ne [cm-3] B||[G] L[pc],  [rad] = RM 2 [m]

Background

Faraday Screen

Foreground


High latitude field with dominating large scale emission.

20% of pixel exceed 3xr.m.s.-noise  FS fraction.


Angle statistics for G109+73relative Effelsberg angles: mean -9.8°, rms 47°absolute Eff.+DRAO angles:mean -36.5°, rms 7°need for RM determination

Field reversal at high latitudes ?


5 GHz RX for large scale polarization mapping at the Urumqi (China) 25m telescope(same 9.4‘ beam as 1.4 GHz EMLS)

MPIfR 5 GHz RX


5 ghz urumqi observations of w1 ngc7822

I (China)

5 GHz Urumqi observations of W1 (NGC7822)

PI towards W1

(on relative level)

Distance = 850 pc

Observed PI =

PIFG– (PIFG + PIBG)

small Faraday effects

in the ISM at 5 GHz

PI


Green bank 300 ft

IAR 30m (China)

Green Bank 300-ft

10m/15m telescope

3-5 RX out of 5–15 GHz band

El-range ~180°

backside of the Moon close

to equator (+/- ~5° latitude)

duration > 2 years ?

Green Bank 300ft


The end
The End (China)


26-m telescope at DRAO/Canada: (China)absolute polarization measurements  > -30° at 1.4 GHz first phase done (undersampled)Thesis Maik Wolleben (2005)

30-m telescope at Villa Elisa/Argentina

I + PI survey at 1.4 GHz



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