Astronomy and Astrophysics – Astrophysics
Scientific paper
2003-06-26
Mon.Not.Roy.Astron.Soc.345:429,2003
Astronomy and Astrophysics
Astrophysics
20 pages, 22 figures; accepted for publication in the MNRAS
Scientific paper
10.1046/j.1365-8711.2003.06948.x
We investigate the evolution of angular momentum in SPH simulations of galaxy formation, paying particular attention to artificial numerical effects. We find that a cold gas disc forming in an ambient hot gas halo receives a strong hydrodynamic torque from the hot gas. By splitting the hydrodynamic force into artificial viscosity and pressure gradients, we find that the angular momentum transport is caused not by the artificial viscosity but by the pressure gradients. Using simple test simulations of shear flows, we conclude that the pressure gradient-based viscosity can be divided into two components: one due to the noisiness of SPH and the other to ram pressure. The former is problematic even with very high resolution because increasing resolution does not reduce the noisiness. On the other hand, the ram pressure effect appears only when a cold gas disc or sheet does not contain enough particles. In such a case, holes form in the disc or sheet, and then ram pressure from intra-hole hot gas, causes significant deceleration. In simulations of galactic disc formation, star formation usually decreases the number of cold gas particles, and hole formation leads to the fragmentation of the disc. To circumvent these problem, we modify the SPH algorithm, decoupling the cold from the hot gas phases, i.e. inhibiting the hydrodynamic interaction between cold and hot particles. This, a crude modelling of a multi-phase fluid in SPH cosmological simulations, leads to the formation of smooth extended cold gas discs and to better numerical convergence. The decoupling is applicable in so far as the self-gravitating gas disc with negligible external pressure is a good approximation for a cold gas disc. (abridged)
Eke Vincent R.
Frenk Carlos S.
Jenkins Alejandro
Okamoto Tohru
Quilis Vicent
No associations
LandOfFree
Momentum transfer across shear flows in Smoothed Particle Hydrodynamic simulations of galaxy formation 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 Momentum transfer across shear flows in Smoothed Particle Hydrodynamic simulations of galaxy formation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Momentum transfer across shear flows in Smoothed Particle Hydrodynamic simulations of galaxy formation will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-335662