galactic radioemission – a problem for precision cosmology ?

Galactic Radioemission – Galactic Radioemission – a problem for precision cosmology ?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./23.3.2005

Summary and ConclusionSummary and Conclusion

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

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

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

Absolutely Calibrated Absolutely Calibrated All-Sky Radio Continuum All-Sky Radio Continuum

SurveysSurveys

408 MHz408 MHzHaslam et al. Haslam et al.

HPBW = 51’, HPBW = 51’, T = 2K T = 2K

1420 MHz1420 MHzReich et al. Reich et al.

HPBW = 35’, HPBW = 35’, T= 50mK T= 50mK

Spectral Index ßSpectral Index ß 408 MHz / 1420 MHz 408 MHz / 1420 MHz

= 2.4 (blue) – 3.0 (red) = 2.4 (blue) – 3.0 (red)Reich et al.Reich et al.

ß

Galactic emissionGalactic emission

mixture of synchrotron ß = 2.4…3.2 mixture of synchrotron ß = 2.4…3.2 + thermal emission ß = 2.1 + 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 absolutely calibrated surveys at

several frequencies neededseveral frequencies needed extrapolation to CMB-Frequencies extrapolation to CMB-Frequencies

uncertainuncertain

Absolute Calibration Sequence for Absolute Calibration Sequence for Total IntensitiesTotal Intensities

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

calibration of medium angular calibration of medium angular resolution all-sky surveysresolution all-sky surveys

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

Absolute „3K“ Absolute „3K“ MeasurementsMeasurements

largely uncertain largely uncertain below below λλ ~ 1cm ~ 1cm

Available surveys

anomalous dust

+212 µK

1.41 GHz Dwingeloo polarization surveyBrouw & 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: Absolute Polarization Calibration: „A Must„A Must“ for Galactic Emission“ for Galactic Emission

Vector additionVector addition for polarisation for polarisation scalar addition for total intensityscalar addition for total intensity

PI = (UPI = (U22 + Q + Q22))1/2 1/2 measuredmeasured ΦΦ = 0.5 atan (U/Q) = 0.5 atan (U/Q) PIPIabsolute absolute = ((U+U= ((U+Uoffoff))22 +(Q+Q +(Q+Qoffoff))22))1/21/2

ΦΦ = 0.5 atan (U = 0.5 atan (U+U+Uoffoff))/(Q/(Q+Q+Qoffoff))

U/Q may be positive or negativeU/Q may be positive or negative

Rotation Measure: RM [rad/m2] RM = 0.81 ne [cm-3] B||[G] L[pc], [rad] = RM 2 [m]

ForegroundForeground

BackgroundBackground

Faraday Screen

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

Angle statistics for G109+73

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 =

PIFG– (PIFG + PIBG)

small Faraday effects in the ISM at 5 GHz

I

PI

Green Bank 300-ft10m/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

Selected surveys