lec10_17oct2011

lec10_17oct2011 - Disk Structure and Evolution (the...

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Disk Structure and Evolution (the so-called α model of disk viscosity) Ge/Ay 133
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Recapitulation of passive disk structure equations. I. and mass surface density, Σ , where the ρ in the equation above right is taken to mean the density at the disk midplane. Equation for hydrostatic equilibrium using only stellar gravity. For an ideal gas where c is the sound speed ( c 2 = R T). Solving yields the scale height, H ,
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Recapitulation of passive disk structure equations. II. In the previous analysis we did not consider that there is a radial pressure gradient, which exerts an acceleration since pressure = force/unit area. Thus, a(pressure)= dPA/m=dPA/ ρ Adr. Balancing gravity, centripetal acceleration, and pressure gives: A dr F=PA Thus, the gas in passive disks moves at slightly sub-Keplerian speeds.
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CO Can only “see” Keplerian v M. Simon et al. 2001, PdBI The CO line shape is sensitive to R disk , M star, , Inc.; but the pressure support is highly sub- Keplerian & similar to v doppler in the outer disk. Dent et al. 2005, JCMT v LSR (km/s) T M B ( K )
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What do other obs. tell us? Radial structure of the MMSN: Mass surface density varies as r -3/2 in this model, what do aperture synthesis observations of circumstellar disks have to say?
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Mm-interferometry observations of disks. I. Overview If you ASSUME the temperature and mass
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lec10_17oct2011 - Disk Structure and Evolution (the...

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