Galactic Radioemission – a problem for precision cosmology ?

1. 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

2. 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)

3. 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

4. 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

5. 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

6. Absolute „3K“ Measurements • largely uncertain below λ ~ 1cm

7. anomalous dust Available surveys

8. +212 µK

10. 1.41 GHz Dwingeloo polarization surveyBrouw & Spoelstra, 1976absolutely calibrated

12. Anticorrelation of I/ PI with Galactic latitude (Reich et al. 1990, Duncan et al. 1999)

13. 24° x 9° section centered at l , b = 162°,0° 1.4 GHz Effelsberg Medium Latitude Survey (EMLS) I PI

14. 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

16. Rotation Measure: RM [rad/m2] RM = 0.81 ne [cm-3] B||[G] L[pc],  [rad] = RM 2 [m] Background Faraday Screen Foreground

17. High latitude field with dominating large scale emission. 20% of pixel exceed 3xr.m.s.-noise  FS fraction.

18. 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 ?

19. 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

20. I 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

21. IAR 30m 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

22. The End

23. 26-m telescope at DRAO/Canada: 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

24. Selected surveys