Planet and Gaps in the disk
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Transcript of Planet and Gaps in the disk
Planet and Gaps in the disk
Hwihyun KimFeb. 8 2006
PAPERS
• Forrest, W. J., et al., 2004, ApJS, 154, 443– “Mid-IR spectroscopy of disks around classical T Tauri star
s”
• Quillen, A. C., et al., 2004, ApJL, 612, L137– “On the planet and the disk of CoKu Tauri/4”
• Varnière, P., et al., 2006, ApJL, 637, L125– “Observational properties of protoplanetary disk gaps”
INTRODUCTION
• Debate– About the nature and time-scales
• Recent discovery of CoKu Tau/4– Young star containing a 10 AU hole (Forrest et al.,
2004) – Link between the inner hole in the disk and the pre
sence of planet– Outer disk is still accreting– Inner hole is left after the formation of a planet
PARAMETERS• Disk viscosity (ν ) :
• Reynolds number (Re) :
• Timescale for the inward accretion (τν) :
– α : viscosity parameter– cs : sound speed– h : scale height– Ω : angular rotation rate– r : radius of orbit
sc h 2Re /r
Re / 2orb :
Wavemaker moon
CLEARING THE INNER DISK
• Planet in the stellar disk forms a hole– Outer disk material is prevented from the accretion
• Presence of the hole– Implies that the inner disk material has time to accret
e onto the star
• For low α and low h – Low viscosity, so high Re : higher τν
– Inner disk has no time to accrete onto the star
• Should be τ p < τν < τ age
GAP OPENING
• Inner disk will begin accreting after a newly formed planet opens a gap
• To open a gap...– Sufficiently massive : q > 40 Re-1
– q = Mp/ M*– Mp of CoKu Tau/4 > 0.1 Mj
PLANET MIGRATION
• Interaction between the planet and surrounding disk
• To maintain the gap, – Balance of the torque density from spiral waves and in
ward torque from viscous accretion
• Mp < Md : outward migration
• CoKu Tau/4 : lack of significant migration
CoKu Tauri/4• Location : Taurus-Auriga cloud• Spectral Type : M1.5 / Mass : 0.5 M⊙
• Luminosity : 0.6 L ⊙ / Distance : 140 pc
• Very special young star– Gap with radius 10 AU– Inner wall with half-height 2 AU
• Gas planet with age < 1 Myr– Suggests that the planet formation can take place quite ea
rly in the evolution of protostellar systems
SPECTRUM
• Excess of emission – 5-8 μ m : characteristic
of accretion disks around young stars
– Beyond 8 μ m : emission from small silicate grains
FM Tau vs. CoKu Tau 4
• FM Tau – Has accretion disk– Actively accreting
• CoKu Tau 4– Decrease in emission in
short-wave IR– Dusty disk with a gap at
10 AU
HOW THE GAP CAN EXIT
• Interactions with the outer disk– Lindblad Resonances → Angular momentum
• Constraints on the mass– Angular momentum → inward migration– MP > M disk edge → no migration
– MP ≤ M disk edge → migration
DISK MORPHOLOGY
• Lindblad resonances
DISK MORPHOLOGY• Proximity of the planet to the disk edge
– More than one resonance– Multiple spiral density waves can be driven at these resonances
• Spiral pattern depends on– Scale height and disk temperature (i.e. Smaller height and cooler disk : tightly
wound)
• High Reynolds number or large planet mass– Disk edge would be far from the planet
INNER HOLES IN DISKS
• Observation– Detected through the study of SEDs– Confirmed by direct images (scattered light ima
ge)– CO line emission in T Tauri stars
• Simulation– Combination of 2D hydrodynamics simulation a
nd 3D Monte Carlo radiative transfer code
SCATTERED LIGHT IMAGE
The top panels : log of the disk surface brightness viewed at an inclination of i = 5
The bottom panels : disks viewed at i = 70
On the left : no gap in the disk
On the right : a gap created by a 2MJ planet at 1 AU
SURFACE BRIGHTNESS PROFILE
• Comparison between the two disks • * : no planet + : 2Mj planet at 1AU• Decrease near the planet and bright bump at the outer edge of
the gap
SPECTRAL ENERGY DISTRIBUTION
• Current instruments – Insufficient spatial resolution– only detect gaps in the outer regions
• SEDs– Indirect detection of planetary gaps– BUT, no unique features
SEDs
• IR SEDs– Left : small-hole (r=0.07 AU)– Right : large-hole (r=1 AU)– Top : ISM dust– Bottom : HH 30 dust (high portion of big grains)– Solid line : with a gap– Dotted line : no gap
http://www.spitzer.caltech.edu/Media/releases/ssc2004-08/ssc2004-
08v3.shtml
SUMMARY
• Recent discovery by Forrest et al.(2004)– Young stellar system with a planet (CoKu Tau 4)– Inner disk has accreted within a time equivalent to the
age of the star(1 Myr)– Planet could be accreting material and interact with th
e disk by driving waves into the disk from resonances
• Simulation of the inner hole in the disk– Direct back illumination by stellar photons of the vertic
al disk wall– Back illumination heats the outer gap wall (emission e
xcess and deficit in SED)