Thursday, August 17, 2006

M. Steinmetz: Cosmic Web - Simulations

The "Cosmic Web" is the structure that arises in cosmological simulations and that is also observed: the universe is clumpy and most of the matter is in huge filametary structures that are made of and connect galaxy clusters.

In simulations the control of the dark matter is much easier than normal matter since it only interacts by gravity. With normal matter, one needs recipies for handling star formation, hydrodynamics have to be taken into account.

Very important: he shows in simulations that a merger may actually look like a disk in kinematical data and he warns the people around Genzel who find "rotating disks" at high redshift. I have to find that movie/paper on the web.

Simulated disks nowadays however seem to fit nicely wit observed ones when it comes to angular momentum. A comparison of a merger with and without AGN feedback is shown and it helps in the sense that otherwise simulated galaxies are too centrally concetrated as compared to real ones.

To test if angular momentum is induced to disks by tidal torques from the cosmic web, it is possible to check the orientations of disks. Indeed there is a correlation between the large scale structure and the orientation of disk galaxies.

The Milky-Way dark matter halo seems to rotate with around 100 km/s as derived from halo star kinematics. But I might have gotten this part wrong. :-)


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