172 research outputs found
Dark Matter Halo Structure in CDM Hydrodynamical Simulations
We have carried out a comparative analysis of the properties of dark matter
halos in N-body and hydrodynamical simulations. We analyze their density
profiles, shapes and kinematical properties with the aim of assessing the
effects that hydrodynamical processes might produce on the evolution of the
dark matter component. The simulations performed allow us to reproduce dark
matter halos with high resolution, although the range of circular velocities is
limited. We find that for halos with circular velocities of at the virial radius, the presence of baryons affects the evolution of
the dark matter component in the central region modifying the density profiles,
shapes and velocity dispersions. We also analyze the rotation velocity curves
of disk-like structures and compare them with observational results.Comment: 28 pages, 15 figures (figures 3ab sent by request), 2 tables.
Accepted for publication MNRA
Stellar feedback from HMXBs in cosmological hydrodynamical simulations
We explored the role of X-ray binaries composed by a black hole and a massive
stellar companion (BHXs) as sources of kinetic feedback by using hydrodynamical
cosmological simulations. Following previous results, our BHX model selects low
metal-poor stars () as possible progenitors. The model that
better reproduces observations assumes that a fraction of
low-metallicity black holes are in binary systems which produce BHXs. These
sources are estimated to deposit erg of kinetic energy per
event. With these parameters and in the simulated volume, we find that the
energy injected by BHXs represents of the total energy released by
SNII and BHX events at redshift and then decreases rapidly as baryons
get chemically enriched. Haloes with virial masses smaller than (or K) are the most directly affected
ones by BHX feedback. These haloes host galaxies with stellar masses in the
range M. Our results show that BHX feedback is able to
keep the interstellar medium warm, without removing a significant gas fraction,
in agreement with previous analytical calculations. Consequently, the
stellar-to-dark matter mass ratio is better reproduced at high redshift. Our
model also predicts a stronger evolution of the number of galaxies as a
function of the stellar mass with redshift when BHX feedback is considered.
These findings support previous claims that the BHXs could be an effective
source of feedback in early stages of galaxy evolution.Comment: 11 pages, 8 figures, accepted for publication in MNRA
Analysis of Galaxy Formation with Hydrodynamics
We present a hydrodynamical code based on the Smooth Particle Hydrodynamics
technique implemented in an AP3M code aimed at solving the hydrodynamical and
gravitational equations in a cosmological frame. We analyze the ability of the
code to reproduce standard tests and perform numerical simulations to study the
formation of galaxies in a typical region of a CDM model. These numerical
simulations include gas and dark matter particles and take into account
physical processes such as shock waves, radiative cooling, and a simplified
model of star formation. Several observed properties of normal galaxies such as
ratios, the luminosity function and the Tully-Fisher
relation are analyzed within the limits imposed by numerical resolution.Comment: 21 pages, 2 postscript tables. Submitted MNRAS 04.03.9
- …