GHz Measurements of anomalous dust emission

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GHz Measurements of anomalous dust emission

• Richard Davis, Clive Dickinson, Rod Davies,
  Anthony Banday
• Paris

2
Ha maps corrected for dust

• Towards a free-free template
• Dickinson, Davies Davis used WHAM and SHASSA Ha
  surveys for the northern and southern skies
• These were corrected for dust absorption using
  100-mm maps of Schlegel Finbeiner Davis
• Cannot recover 5 of sky along galactic plane

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Dust corrected H alpha
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Conversion of dust corrected Ha 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

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Free-free brightness temperature 5?K 1mK in
powers of 2 at 30 GHz
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Dust map shows regions where absorption is too
high
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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 bgt20
• 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

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Foreground contribution
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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 100?m
  total dust emission
• The amplitude is 500 times that expected from
  thermal dust emission

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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

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Correlation slope spectra for l0,15,30,45
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Model emissivity
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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.

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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

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Spectrum of G159.6-18.5
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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

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COBE DMR maps
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Templates for COBE data

• Dust is traced by the140-mm 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

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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

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Coupling coefficient foregrounds thermal dust
subtracted and dust emissivity
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Template coefficients
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Foreground contamination in ?K

• The coupling coefficients are multiplied by the
  foregrounds to obtain the contamination of the
  CMB
• This is for bgt20
• Synchrotron is dotted line
• Free-free is dot-dashed line
• Thermal dust is dashed line
• Anomalous dust is heavy dashed line

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Anomalous Dust
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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

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microK/Mega Jy/sr
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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

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W40 microK/MegaJy/sr