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Improved Model of Spinning Dust Emission and Implications

This research presents an improved model of spinning dust emission, incorporating realistic grain dynamics and shapes. By utilizing WMAP data, physical parameters of dust are constrained. Future works will explore polarization effects for CMB B-mode experiments.

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Improved Model of Spinning Dust Emission and Implications

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  1. Improved Model of Spinning Dust Emission and Implications Thiem Hoang (UW-Madison) in collaboration with Alex Lazarian (UW-Madison), Bruce T. Draine (Princeton)

  2. Outline • Motivation • Galactic Foregrounds to CMB and Anomalous Microwave Emission (Clive’s talk) • Draine & Lazarian Model (DL98, Alex’s talk) • Improved Model of Spinning Dust • Constraining Physical Parameters using WMAP data • Summary and Future Works

  3. Motivation: Precision Cosmology cleaning K band (23 GHz) LAMBDA Understanding Galactic Foregrounds Spergel et al. 2003

  4. Improved Model of Spinning Dust Step 1: Improve grain rotational dynamics -Grain precession, internal relaxation (Hoang, Draine & Lazarian 2010, ApJ 465, 1602) Silsbee, Ali-Haimoud & Hirata 2011: Grain precession, no internal relaxation Step 2: Deal with realistic grain shape - Triaxial ellipsoid (irregular shape) - Grain wobbling (Hoang, Lazarian, & Draine 2011, submitted, ArXiv 1105.2302)

  5. What are small dust grains? PAHs Irregular shape! Disk-like shape (DL98 model)

  6. Step 1: Grain Precession PAH 1D rotation DL98 model Ĵ a3 μ a1 modeling θ μ HDL10 a2 our new model μ Grain wobbling Grain precession

  7. Spinning Dust: Power Spectrum  Torque-free motion: Euler angles ϕ, ψ, θ, and rates  Electric dipole moment:  Fourier Transform:  Power Spectrum: a3 Ĵ a3 a1 μ θ a2 Ĵ

  8. Power Spectrum ω/(J/I1) 1 DL98  Precessing grain radiates at frequency modes:  Dominant modes: What makes dust grain rotating?

  9. Rotational Damping and Excitation H (R~ 10-7 /s) H IR emission (~102 s after UV absorption) UV photon (R~10-8 /s) PAH ion

  10. Numerical Method: Langevin Equations  Angular momentum J in the lab system is described by Langevin equations (LEs): Integrate LEs to get J(t) and find momentum distribution fJ Emissivity per H atom: 

  11. Emission Spectrum our result DL98 DL98 our result HDL10  Peak emissivity increases by a factor ~2 .  Peak frequency increases by factors ~1.4 to 1.8.

  12. Step 2: Irregular Shape Irregular shape! Disk-like shape, (DL98) What is the effect of irregular shape?

  13. J Power Spectrum DL98  Multiple frequency modes: where <…> denotes time averaging. HLD11 a1 μ

  14. Emission Spectrum Working model: Simple irregular shape Irregularity: η=b3/b2 η=b3/b2 case 1 (μ1=μ/31/2)

  15. Emissivity increases with η • ★ Emissivity increases with Tvib

  16. Constraining Physical Parameters:Fitting to WMAP data CMB5 Dobler, Draine & Finkbeiner 2009

  17. Fitting to Hα-correlated spectrum Model: Minimizing  Fitting parameters: F0: e temperature Sd0: variation of PAH abundance C0: CMB bias Spinning dust parameters: nH, dipole moment β0

  18. ★ F0=0.09 Te~ 2500K (Dong & Draine 2011 explain low Te) ★ Sd0=0.06 PAH depleted in WIM ★ Dipole β0~ 0.65 D, nH ~0.11 cm-3 20 40 100

  19. Summary and Future Works • Improved model accounts for wobbling grain, irregular shape • internal relaxation, transient events. • 2. Improved model can reproduce high peak frequency in Hα-correlated spectrum from WMAP data. • 3. Improved model can be used to diagnose dust physical parameters. • Future works will address polarization from spinning dust and implications to B-mode of CMB polarization experiments. J J a1 μ μ DL98 Thank you!

  20. Thermal Dust-Correlated Spectrum ★ T0=0.8 ★ Sd0 ~ 0.9 ★ β0=0.95 D,nH ~10 cm-3

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