1 / 10

Physics 778 – Star formation: Protostellar disks

Physics 778 – Star formation: Protostellar disks. Ralph Pudritz. 1.2 Disk evolution – reading spectral energy distributions (SEDs). d(log l F l ) / d(log l ) ( 1 – 10 m m). I. II. > 0 Class I < 0 y > -3 Class II ~ -3 Class III (photosphere). III.

hao
Download Presentation

Physics 778 – Star formation: Protostellar disks

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Physics 778 – Star formation: Protostellar disks Ralph Pudritz

  2. 1.2 Disk evolution – reading spectral energy distributions (SEDs) d(log l Fl) / d(log l) ( 1 – 10 mm) I II > 0 Class I < 0 y > -3 Class II ~ -3 Class III (photosphere) III from Hartmann 1998

  3. SEDs from Spitzer spectra: Class 0: (bottom) L1448C Class 1: (yellow) IRAS 04016+ Class II: (green) different small dust composition Class III (top, blue) (spectra from FM Tau down offset by factors 50, 200, and 10,000). Most prominent feature; ices and minerals Annual Reviews

  4. Class 1 Excess of energy above photosphere In IR - mm photosphere from Hartmann 1998

  5. 1.3 Disk formation - gravitational collapse of rotating molecular cloud core • Particles free-fall conserving specific angular momentum l • l ~ ro2W sin q, for particle falling from ro in core with uniform angular velocity W and angle q from rotation axis • Higher l for larger separation from rotation axis W r0

  6. Particle from ro,q shocks with particle from ro,q+p on equatorial plane, vertical velocity component dissipated, particles keep rotating on equatorial plane in a disk • Particles with q ~ p/2, reach the equatorial plane at the centrifugal radius Rc = ro4W2 / GM, M central mass, Rc ~ disk radius

  7. Collapse: streamlines and disk formation… • Streamlines at constant intervals of cos q • (dM/dt) ~ D cos q (dM/dt)/2 =>Mass accumulates at Rc M(core) at large radius => most of the core mass into the disk from Hartmann 1998

  8. 1.4 Accretion disks: viscous evolution • Particles at R rotating with W(R) move to R+DR, while particles at R+DR rotating at W(R+DR) < W(R) move to R. This motion implies a change of J in time, ie, a torque: • Tviscous ~ 2 pSn R3 dW/dR • where S = surface density; n = viscosity • ~ v l, where v and l are characteristic velocity and length of the turbulent motions - uncertain a prescription: n = a cs H, where cs is the sound speed and H the scale height (Shakura & Sunnyaev 1973).

  9. Viscous evolution of a ring: exact mathematical solution (see Pringle, ARAA, 1981) t=0 all angular momentum at infinity, carried by e of the mass t >> R12/n: all mass at center

  10. Disk evolution: expression for viscosity n= a cs H, cs sound speed, H = cs/W n = cs2/W = const T R3/2 In an irradiated disk at large R, T as 1/R1/2 So, n ~ const. R Similarity solution for S (R,t) (see Hartmann et al. 1998)

More Related