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

Summary and Conclusion Scientific needs: absolutely calibrated sky surveys in I and PI between ~5-15 GHz 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 Technical needs: 10m/15m meridian telescope operating at 3-5 frequencies Location: backside of the moon close to equator (+/- ~5° latitude) Location: backside of the moon close to equator (+/- ~5° latitude)

Absolutely Calibrated All-Sky Radio Continuum Surveys 408 MHz Haslam et al. HPBW = 51’,  T = 2K 1420 MHz Reich et al. HPBW = 35’,  T= 50mK Spectral Index ß 408 MHz / 1420 MHz  = 2.4 (blue) – 3.0 (red) Reich et al. ß

Galactic emission mixture of synchrotron ß = 2.4…3.2 + thermal emission ß = 2.1 mixture of synchrotron ß = 2.4…3.2 + thermal emission ß = 2.1 anomalous dust: 10 GHz – 30 GHz ? anomalous dust: 10 GHz – 30 GHz ? component separation difficult component separation difficult absolutely calibrated surveys at several frequencies needed absolutely calibrated surveys at several frequencies needed extrapolation to CMB-Frequencies uncertain extrapolation to CMB-Frequencies uncertain

Absolute Calibration Sequence for Total Intensities Absolute skyhorn measurements ~10°/15° angular resolution 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

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

Available surveys anomalous dust

+212 µK

1.41 GHz Dwingeloo polarization survey Brouw & Spoelstra, 1976 absolutely calibrated

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) I PI

Absolute Polarization Calibration: „A Must“ for Galactic Emission Vector addition for polarisation scalar addition for total intensity Vector addition for polarisation scalar addition for total intensity PI = (U 2 + Q 2 ) 1/2 measured PI = (U 2 + Q 2 ) 1/2 measured Φ = 0.5 atan (U/Q) Φ = 0.5 atan (U/Q) PI absolute = ((U+U off ) 2 +(Q+Q off ) 2 ) 1/2 PI absolute = ((U+U off ) 2 +(Q+Q off ) 2 ) 1/2 Φ = 0.5 atan (U +U off ) /(Q +Q off ) Φ = 0.5 atan (U +U off ) /(Q +Q off ) U/Q may be positive or negative 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] Foreground Background Faraday Screen

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

Angle statistics for G relative 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) PI towards W1 (on relative level) Distance = 850 pc Observed PI = PI FG – (PI FG + PI BG ) small Faraday effects in the ISM at 5 GHz I PI

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 IAR 30m

The End

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

Calibration of 1.4 GHz Polarization Surveys Northern Sky Southern Sky Dwingeloo 25m Absolute Scale undersampled Incomplete coverage DRAO 26m Scans in RA, 36’ All-Sky Survey HPBW 36´ EMLS 100m +/-20°, 9.4’ DRAO CGPS +5°/-4°, 1’ Villa Elisa 30m Fully sampled, 36’ ATCA Plane Survey 1´ Parkes 64m 14.5’ Extended sources x 0.85 T b (MB)

Selected surveys

Structures change on absolute level Large field > 10°x10° with small losses in PI