2 research outputs found
Angular Momentum Profiles of Warm Dark Matter Halos
We compare the specific angular momentum profiles of virialized dark halos in
cold dark matter (CDM) and warm dark matter (WDM) models using high-resolution
dissipationless simulations. The simulations were initialized using the same
set of modes, except on small scales, where the power was suppressed in WDM
below the filtering length. Remarkably, WDM as well as CDM halos are
well-described by the two-parameter angular momentum profile of Bullock et al.
(2001), even though the halo masses are below the filtering scale of the WDM.
Although the best-fit shape parameters change quantitatively for individual
halos in the two simulations, we find no systematic variation in profile shapes
as a function of the dark matter type. The scatter in shape parameters is
significantly smaller for the WDM halos, suggesting that substructure and/or
merging history plays a role producing scatter about the mean angular momentum
distribution, but that the average angular momentum profiles of halos originate
from larger-scale phenomena or a mechanism associated with the virialization
process. The known mismatch between the angular momentum distributions of dark
halos and disk galaxies is therefore present in WDM as well as CDM models. Our
WDM halos tend to have a less coherent (more misaligned) angular momentum
structure and smaller spin parameters than do their CDM counterparts, although
we caution that this result is based on a small number of halos.Comment: 5 pages, 1 figure, Submitted to ApJ
The agora high-resolution galaxy simulations comparison project
We introduce the Assembling Galaxies Of Resolved Anatomy (AGORA) project, a comprehensive numerical study of well-resolved galaxies within the ÎCDM cosmology. Cosmological hydrodynamic simulations with force resolutions of ~100 proper pc or better will be run with a variety of code platforms to follow the hierarchical growth, star formation history, morphological transformation, and the cycle of baryons in and out of eight galaxies with halo masses Mvir 1010, 1011, 1012, and 1013 Mâ at z = 0 and two different ("violent" and "quiescent") assembly histories. The numerical techniques and implementations used in this project include the smoothed particle hydrodynamics codes GADGET and GASOLINE, and the adaptive mesh refinement codes ART, ENZO, and RAMSES. The codes share common initial conditions and common astrophysics packages including UV background, metal-dependent radiative cooling, metal and energy yields of supernovae, and stellar initial mass function. These are described in detail in the present paper. Subgrid star formation and feedback prescriptions will be tuned to provide a realistic interstellar and circumgalactic medium using a non-cosmological disk galaxy simulation. Cosmological runs will be systematically compared with each other using a common analysis toolkit and validated against observations to verify that the solutions are robustâi.e., that the astrophysical assumptions are responsible for any success, rather than artifacts of particular implementations. The goals of the AGORA project are, broadly speaking, to raise the realism and predictive power of galaxy simulations and the understanding of the feedback processes that regulate galaxy "metabolism." The initial conditions for the AGORA galaxies as well as simulation outputs at various epochs will be made publicly available to the community. The proof-of-concept dark-matter-only test of the formation of a galactic halo with a z = 0 mass of Mvir 1.7 Ă 1011 Mâ by nine different versions of the participating codes is also presented to validate the infrastructure of the project