Zodiacal Cloud: The Local Circumstellar Disk Sumita Jayaraman

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

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

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

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

PSI Resonant Trapping of Dust Particles

PSI Resonance Capture Probability vs Particle Size

PSI Earth’s Resonant Ring Model Sun Spitzer’s Orbit

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

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

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

PSI 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.

PSI Spitzer Zodical Obs. Obs. ModeDirection of Obs.Instrument Fast Scan- Map ~ -6 ° to +6 ° Ecliptic Latitude MIPS TPM Poles+90 ° and -90 °IRAC & MIPS TPM Ecliptic (Trailing and Leading) 0 ° Ecliptic Latitude ε =70 °, 90 °, 110 ° 60 ° Ecliptic Latitude ε =90° IRAC & MIPS

PSI Spitzer Project: Planned Obs Leading Trailing

PSI IRAC North Ecliptic Pole Flux 2004

PSI IRAC North Ecliptic Pole Flux

PSI IRAC North Ecliptic Pole Flux

PSI MIPS North Ecliptic Pole Flux

PSI Ring: Model vs Observations EarthRing Model: 10 micron particles into First order resonances Spitzer Earthring Observations 2004: None 2006: 10% increase of in the NEP Flux at the maximum point 2004: None 2006 (May): 6% (1.1MJy increase in the NEP Flux)

PSI 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.

PSI 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?

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

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

PSI Sun-Centered Cloud Sun Earth Orbit Zodiacal Center Earth Aphelion

PSI Off-Center Cloud Sun Earth Orbit Zodiacal Center Earth Aphelion

PSI Evidence for an off-center cloud

PSI Inclination of the cloud

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

PSI Zodiacal Peak-Flux Variation without the Ring

PSI Zodiacal Peak-Flux Variation due to Earth’s eccentricity

PSI Warps in the Zodiacal cloud

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

PSI Asteroidal Dust Bands Scan

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

PSI 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.

PSI 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.

PSI 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)

PSI ε Eridani (Quillen & Thornedike, 2002) e = 0.3 M = MSun A = 40 A.U.

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

PSI 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.