Nonlinear Outcome of Gravitational Instability in Disks with Realistic Cooling

Details Nonlinear Outcome of Gravitational Instability in Disks with Realistic Cooling Nonlinear Outcome of Gravitational Instability in Disks with Realistic Cooling

2003-12-18

arxiv.org/abs/astro-ph/0312507v1

Astrophys.J. 597 (2003) 131-141

Astronomy and Astrophysics

Astrophysics

30 pages, 12 figures

Scientific paper

10.1086/378392

We consider the nonlinear outcome of gravitational instability in optically thick disks with a realistic cooling function. We use a numerical model that is local, razor-thin, and unmagnetized. External illumination is ignored. Cooling is calculated from a one-zone model using analytic fits to low temperature Rosseland mean opacities. The model has two parameters: the initial surface density Sigma_0 and the rotation frequency Omega. We survey the parameter space and find: (1) The disk fragments when t_c,eff Omega = 1, where t_c,eff is an effective cooling time defined as the average internal energy of the model divided by the average cooling rate. This is consistent with earlier results that used a simplified cooling function. (2) The initial cooling time t_c0 or a uniform disk with Q = 1 can differ by orders of magnitude from t_c,eff in the nonlinear outcome. The difference is caused by sharp variations in the opacity with temperature. The condition t_c0 Omega = 1 therefore does not necessarily indicate where fragmentation will occur. (3) The largest difference between t_c,eff and t_c0 is near the opacity gap, where dust is absent and hydrogen is largely molecular. (4) In the limit of strong illumination the disk is isothermal; we find that an isothermal version of our model fragments for Q < 1.4. Finally, we discuss some physical processes not included in our model, and find that most are likely to make disks more susceptible to fragmentation. We conclude that disks with t_c,eff Omega < 1 do not exist.

Affiliated with

Also associated with

No associations

Rating

Nonlinear Outcome of Gravitational Instability in Disks with Realistic Cooling does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Nonlinear Outcome of Gravitational Instability in Disks with Realistic Cooling, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Nonlinear Outcome of Gravitational Instability in Disks with Realistic Cooling will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-198016