| Original Articles |
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Detection of a Physical Difference between the CDM Halos in Simulation and in Nature |
| XIAO Wei-Ke1;PENG Chang1;YE Xian-Feng1;HAO Heng2 |
| 1Center for Astrophysics, University of Science and Technology of China, Hefei 230026
2Department of Astronomy, Harvard University, 60 Garden Street, Cambridge, MA 02138, USA |
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| Cite this article: |
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XIAO Wei-Ke, PENG Chang, YE Xian-Feng et al 2006 Chin. Phys. Lett. 23 1355-1358 |
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Abstract Numerical simulation is an important tool that is helpful for us to understand the process of structure formation in the universe. However, many simulation results of cold dark matter (CDM) halos on a small scale are inconsistent with observations: the central density profile is too cuspy and there are too many substructures. Here we point out that both the problems may be connected with a hitherto unrecognized bias in the simulated halos. Although CDM halos in nature and in simulation are both virialized systems of collisionless CDM particles, gravitational encounter cannot be neglected in the simulated halos because they contain many fewer particles. We demonstrate this by two numerical experiments, showing that there is a difference on the microcosmic scale between the natural and simulated halos. The simulated halo is more akin to globular clusters where gravitational encounter is known to lead to such drastic phenomena as core collapse. Such an artificial core collapse process appears to link the two problems together in the bottom-up scenario of structure formation in the ΛCDM universe. The discovery of this bias also has implications on the applicability of the Jeans theorem in galactic dynamics.
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| Keywords:
95.35.+d
98.80.-k
95.75.-z
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Published: 01 May 2006
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| PACS: |
95.35.+d
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(Dark matter)
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98.80.-k
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(Cosmology)
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95.75.-z
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(Observation and data reduction techniques; computer modeling and simulation)
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