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GHz Measurements of anomalous dust emission
Richard Davis, Clive Dickinson, Rod Davies, Anthony Banday
Paris
H maps corrected for dust
• Towards a free-free template
• Dickinson, Davies & Davis used WHAM and SHASSA H surveys for the northern and southern skies
• These were corrected for dust absorption using 100-m maps of Schlegel Finbeiner & Davis
• Cannot recover 5% of sky along galactic plane
Conversion of dust corrected H into predicted radio surface
brightness• The free-free emission formula has been
revised to give a 1% accurate formula for 100MHz-100GHz and electron temperature for 3000-20000K
• A full-sky free-free template map is presented at 30GHz.
• The Haslam 408MHz all sky map can be corrected to give a pure synchrotron map
Quest for foreground X
• Oliveira-Costa et al. take the WMAP ‘synchrotron’ template and correlate this with the Tenerife 10 and 15 GHz data and the individual WMAP frequencies for |b|>20°
• On the plot they show a synchrotron -2.8 and spinning dust spectrum from Draine & Lazarian added to a 20K thermal dust component normalized to 90GHz
Microwave emission in Green Bank Galactic Plane Survey
• Finkbeiner et al measure a rising spectrum from 8.3 to 14.3 GHz in a survey of the Galactic Plane
• They produce a free-free corrected 14.3 corrected (superposition) which correlates well with 100m total dust emission
• The amplitude is 500 times that expected from thermal dust emission
Combination of Rhodes 2.3GHz, Green Bank 8.3 and 14 .3 GHz and WMAP Galactic Plane data
• Each frequency channel antenna temperature is plotted against the WMAP 94GHz channel with the CMB removed and good correlations are found
• These eight frequency channels correlation slopes are then plotted against frequency
Large-scale anomalous microwave from WMAP
G.Lagache
• Residual emission is found from WMAP over free-free and synchrotron with a constant spectrum from 3.2 to 9.1mm and decreases in amplitude when NHI increases
• They propose that the excess is associated with small transiently heated dust particles.
Detection of anomalous microwave emission in the Perseus Moleular cloud
• Cosmosomas finds direct evidence for anomalous microwave emission with a rising spectrum from 11 to 17 GHz
Reappraising foreground contamination in COBE-DMR
• Banday et al 03 take the best foregrounds we have and correlate with DMR
• They find a strong anomalous dust component peaking ~20 GHz
Templates for COBE data• Dust is traced by the140-m DIRBE sky
map,all templates are convolved to 7°
resolution
• The free-free template is traced by the H map from Dickinson, Davies & Davis as described above
• The Synchrotron template is based on the Haslam 408 MHz
Derivation of coupling coefficients of foregrounds with COBE DMR
• In this analysis we treat multiple foreground templates and all three DMR channels simultaneously. This forces the CMB distribution to be invariant between the three frequencies.
• Correlation of each foreground with each COBE frequency gives the coupling coefficients
• Thermal dust has been removed from the DMR data by using the template from Finkbeiner, Davis & Schlegel
Foreground contamination in K• The coupling coefficients are multiplied by
the foregrounds to obtain the contamination of the CMB
• This is for b>|20°|
• Synchrotron is dotted line
• Free-free is dot-dashed line
• Thermal dust is dashed line
• Anomalous dust is heavy dashed line
Quantitative comparison of anomalous dust
• A careful of the calibration of work on anomalous dust
• Getting the numbers all into microK/megaJy/sr
• Finkbeiner on plane• Watson Cosmosomas on G159.6-18.5 in
Perseus Molecular cloud• Banday diffuse off the plane
microK/Mega Jy/sr
1
10
100
1000
1 10 100GHz
microK/Mjy/sr Finkbeiner et al 2004
Cosmosomas
Banday et al 2004
Finkbeiner W40
• The same calibration was done on W40 which shows a similar spectrum
• The lowest frequency was assumed to be mostly free-free and a -0.13 index was subtracted to get the true anomalous emission , if the above assumption is true