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Improved Model of Spinning Dust Emission and Implications

Improved Model of Spinning Dust Emission and Implications. Thiem Hoang (UW-Madison) in collaboration with Alex Lazarian (UW-Madison), Bruce T. Draine (Princeton). Outline. Motivation Galactic Foregrounds to CMB and Anomalous Microwave Emission (Clive’s talk)

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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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