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Planet Formation in a disk with a Dead Zone

Planet Formation in a disk with a Dead Zone. Soko Matsumura (Northwestern University) Ralph Pudritz (McMaster University) Edward Thommes (Northwestern University). Planet formation and migration in an evolving disk with a dead zone.

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Planet Formation in a disk with a Dead Zone

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  1. Planet Formation in a disk with a Dead Zone Soko Matsumura (Northwestern University) Ralph Pudritz (McMaster University) Edward Thommes (Northwestern University)

  2. Planet formation and migration in an evolving disk with a dead zone • Pollack et al. (1996), Hubickyj et al. (2005): giant planet formation at a fixed orbital radius (~ 5.2 AU) with no disk evolution • Alibert et al. (2005) studied giant planet formation with migration and disk evolution, and found that planet migration can speed up the formation. • Jupiter can be made within about 106 years. • Planet migration has to be at least 10 times slower. • One of the problems of the core accretion scenario: planet migration seems to be too fast.

  3. 30 α = 10-2 20 Disk radius [AU] 10 α = 10-5 0 0 2x106 4x106 6x106 8x106 107 Time [years] Planet formation and migration in an evolving disk with a dead zone • If a planet is made outside the dead zone, we may not need to artificially slow down the planet migration.

  4. Dead Zone Evolution of Dead Zones • Gammie (1996): Mass accretion through the surface layers can explain the observed mass accretion rate onto the central star.

  5. αactive αdead Evolution of Dead Zones • Averaged viscosity

  6. 100 30 10 20 1 Disk radius [AU] Disk radius [AU] 10 0.1 0.01 0 104 105 106 107 0 2x106 4x106 6x106 8x106 107 Time [years] Time [years] Evolution of Dead Zones

  7. 100 106 104 10 102 Surface mass density Σ [g cm-2] 1 Disk radius [AU] 1 10-2 0.1 10-4 0.01 0.1 1. 10. 100. 0.01 Disk radius [AU] 104 105 106 107 Time [years] Evolution of Dead Zones Mdisk~ 0.01 Msolar 107 yrs 106 yrs 105 yrs 104 yrs Mdisk< MJ

  8. Pollack et al. (1996) Planet Formation (core accretion scenario) • Core accretion + Gas accretion

  9. Planet Formation (core accretion scenario) • Core accretion • Rapid core growth upto ~10-3 -10-2 ME (Ida & Makino 1993) • Oligarchic growth (e.g. Kokubo & Ida 1998, Thommes et al. 2003) • Gas accretion • Scaled with Kelvin-Helmholtz timescale (e.g. Pollack et al. 1996, Ikoma et al. 2000, Bryden et al. 2000, Ida & Lin 2004)

  10. 100 Total 10 Core 1 Mass [ME] 0.1 Envelope 0.01 0.001 0 2x106 4x106 6x106 8x106 107 Time [years] Planet Formation (core accretion scenario) • Pollack et al. (1996): Jupiter can be made within 8 x 106 years at 5.2 AU. • Use the solid surface mass density: Σs = 300(r/AU)-2 g cm-2 and a planetesimal size (10km). • Oligarchic growth is slower than runaway growth.

  11. 100 Total 10 Core 1 Mass [ME] 0.1 Envelope 0.01 0.001 0 2x106 4x106 6x106 8x106 107 Time [years] Planet Formation (core accretion scenario) • Lower opacity speeds up gas accretion (e.g. Ikoma et al. 2000, Hubickyj et al. 2005). • Hubickyj et al. (2005): Jupiter can be made within a few 106 years. • Use a fixed opacity of 0.03 cm2 g-1.

  12. 100 10 1 Disk radius [AU] 0.1 0.01 0 2x106 4x106 6x106 8x108 Time [years] Planet Formation in a disk with a dead zone • Initial disk mass is Md ~ 0.01 Msolar and disk temperature is calculated as in Chiang et al. (2001). • Dead zone is initially stretched out to ~ 13 AU. • Planetary core with 0.6 ME is placed at 10 AU. • Standard opacity (1 cm2 g-1) assumed.

  13. 100 100 10 10 1 1 Disk radius [AU] Disk radius [AU] 0.1 0.1 0.01 0.01 0 2x106 4x106 6x106 8x108 0 2x106 4x106 6x106 8x108 Time [years] Time [years] Planet Formation in a disk with a dead zone Decreased opacity (0.03 cm2 g-1) Standard opacity (1 cm2 g-1)

  14. 100 100 10 10 1 1 Mass [ME] Mass [ME] 0.1 0.1 0.01 0.01 0.001 0.001 0 2x106 4x106 6x106 8x106 0 2x106 4x106 6x106 8x106 Time [years] Time [years] Planet Formation in a disk with a dead zone Standard opacity (1 cm2 g-1) Decreased opacity (0.03 cm2 g-1) Core Total Envelope

  15. 100 10 1 Disk radius [AU] 0.1 0.01 0 2x106 4x106 6x106 8x106 107 Time [years] Planet Formation in a disk with a dead zone • Planetary core with 0.6 ME is placed at 15 AU. • Core accretion is truncated at 10 ME. • Standard opacity is assumed.

  16. 100 1000 10 100 Mass [ME] 10 1 Disk radius [AU] 1 0.1 0.1 104 105 106 107 0.01 0 2x106 4x106 6x106 8x106 107 Time [years] Time [years] Planet Formation in a disk with a dead zone

  17. Summary • Dead zones evolve rapidly. • From 13 AU to 1 AU within ~ 2 x 106 years. • Dead zones help planet formation by slowing down the migration. • Core mass as well as the difference in viscosities between active and dead zones may affect the evolution of a planet.

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