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Zodiacal Cloud: The Local Circumstellar Disk

Zodiacal Cloud: The Local Circumstellar Disk. Sumita Jayaraman. Why do we study the Zodiacal Cloud?. For the Solar System. Yields information on the formation and evolution of the interplanetary dust disk in our Solar System. For Exo-zodi Disks and Planetary Systems.

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Zodiacal Cloud: The Local Circumstellar Disk

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  1. Zodiacal Cloud: The Local Circumstellar Disk Sumita Jayaraman

  2. Why do we study the Zodiacal Cloud? For the Solar System Yields information on the formation and evolution of the interplanetary dust disk in our Solar System. For Exo-zodi Disks and Planetary Systems Direct application to the structure of exo- zodi disks and planetary detection.

  3. Contents Structures in the zodiacal cloud • Earth’s Resonant Ring • Dynamical Asymmetries • Dust Bands Structures in Exo-zodiacal disks

  4. Contents Structures in the zodiacal cloud • Earth’s Resonant Ring • Dynamical Asymmetries • Dust Bands Structures in Exo-zodiacal disks

  5. Zodiacal Peak-Flux Variation (COBE-DIRBE) Average Trailing: 70.26 MJ/Sr Average Leading: 68.5 MJy/Sr Ring Flux : 1.7 MJy/Sr (~2.5%)

  6. Resonant Trapping of Dust Particles

  7. Resonance Capture Probability vs Particle Size

  8. Earth’s Resonant Ring Model Spitzer’s Orbit Sun

  9. All-Sky View of Ring Trailing Leading At Spitzer Launch… …After 2 years Estimated Ring Flux: ~ 5.5 MJy/Sr (8% of Zody)

  10. Resonant Ring Obs. 25μm (COBE-DIRBE) Trailing Leading (Reach et al., 1995)

  11. All Sky Model for Extended Spitzer Mission At Launch Year 1 Year 2 Year 3 Year 4 Year 5

  12. Goals of the Spitzer Project • Track measurements of the Earth’s Resonant Ring as Spitzer traverses it. • Monitor variations in the Ecliptic Pole flux. • Measure the absolutely calibrated zodiacal flux and estimate background radiation levels during the mission. • Obtain very high resolution images of the asteroidal dust bands.

  13. Spitzer Zodical Obs.

  14. Spitzer Project: Planned Obs Trailing Leading

  15. IRAC North Ecliptic Pole Flux 2004

  16. IRAC North Ecliptic Pole Flux 2004 2005

  17. IRAC North Ecliptic Pole Flux 2004 2005 2006

  18. MIPS North Ecliptic Pole Flux 2004 2005 2006

  19. Ring: Model vs Observations

  20. Next Steps • Analysis of Ecliptic Plane Observations (predicted increase in ring flux from 2.5%(1.7 MJy/Sr) of zody to 8% (5.5 MJy/Sr) of zody) • Multiple Wavelength observations (3.6 and 70 microns) from IRAC, MIPS as well as IRS Peak-up mode.

  21. Science Questions • What is number density of particles in the ring? • What is the background number density required to produce the flux variations? • What is the efficiency of capture into resonance by an Earth-mass planet? • How do we distinguish a feature like trailing dust cloud in ring from the planetary perturber in an exozodiacal disk?

  22. Contents Structures in the zodiacal cloud • Earth’s Resonant Ring • Dynamical Asymmetries • Dust Bands Structures in Exo-zodiacal disks

  23. Dynamical Asymmetries in the Zodiacal cloud • Off-center shift of the zodiacal cloud shown by the pole observations. • Warps in the cloud due to the inclination and shift measured by the variations in peak flux.

  24. Sun-Centered Cloud Zodiacal Center Earth Orbit Sun Earth Aphelion

  25. Off-Center Cloud Zodiacal Center Earth Orbit Sun Earth Aphelion

  26. Evidence for an off-center cloud

  27. Inclination of the cloud

  28. Zodiacal Peak-Flux Variation (COBE-DIRBE) Ring Flux : 1.7 MJy/Sr (~2.5%)

  29. Zodiacal Peak-Flux Variationwithout the Ring

  30. Zodiacal Peak-Flux Variationdue to Earth’s eccentricity

  31. Warps in the Zodiacal cloud

  32. Contents Structures in the zodiacal cloud • Earth’s Resonant Ring • Dynamical Asymmetries • Dust Bands Structures in Exo-Zodiacal disks

  33. Asteroidal Dust Bands Scan

  34. Contents Structures in the zodiacal cloud • Earth’s Resonant Ring • Dynamical Asymmetries • Dust Bands Structures in Exo-zodiacal disks

  35. Dynamical Effects in Circumstellar Disks • Resonant trapping – determined by the number and co-rotation of the clumps • Recent planetesimal collisions in the disk – young dust bands • Planetary perturbations on the disk due to one or more planets causing an inclined and off-center disk.

  36. Planetary Signatures in Observed Disks • Resonant Rings caused by larger Planets - ε Eridani • Off-center disk – HR4796A • Gaps in the disk due to Resonant Trapping and scattering due to Large Planet – β Pictoris ? • Warps in the disk due to planetary perturbations - β Pictoris. • Bands due to stochastic collisions.

  37. What do the structures tell us? • Location of the planet(s), eccentricity of the orbit • Mass of the planet(s) • Size of the dust particles (lower limits)

  38. ε Eridani (Quillen & Thornedike, 2002) e = 0.3 M = 10- 4 MSun A = 40 A.U.

  39. HR 4796A (Wyatt et al. 2002) Flux Asymmetry ~ 5% Estimate of Planet Mass > 10 Mass of Earth with e >0.02

  40. Challenges in Planetary Detection in Disks • Young disks have dust and gas • Structures observed in images do not provide unique solutions for planetary masses or location • Source of dust is uncertain – especially for disks with small dust grains.

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