417 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
SPH simulations of the chemical evolution of bulges
We have implemented a chemical evolution model on the parallel AP3M+SPH DEVA
code which we use to perform high resolution simulations of spiral galaxy
formation. It includes feedback by SNII and SNIa using the Qij matrix
formalism. We also include a diffusion mechanism that spreads newly introduced
metals. The gas cooling rate depends on its specific composition. We study the
stellar populations of the resulting bulges finding a potential scenario where
they seem to be composed of two populations: an old, metal poor,
-enriched population, formed in a multiclump scenario at the beginning
of the simulation and a younger one, formed by slow accretion of satellites or
gas, possibly from the disk due to instabilities.Comment: 2 pages, 3 figures. Proceedings of IAUS 245 "Formation and Evolution
of Galaxy Bulges
Large Scale Morphological Segregation in Optically Selected Galaxy Redshift Catalogs
We present the results of an exhaustive analysis of the morphological
segregation of galaxies in the CfA and SSRS catalogs through the scaling
formalism. Morphological segregation between ellipticals and spirals has been
detected at scales up to 15-20 h Mpc in the CfA catalog, and up to 20-30
h Mpc in the SSRS catalog. Moreover, it is present not only in the
densest areas of the galaxy distribution, but also in zones of moderate
density.Comment: 9 pages, (1 figure included), uuencode compressed Postscript,
(accepted for publication in ApJ Letters), FTUAM-93-2
Lagrangian Volume Deformations around Simulated Galaxies
We present a detailed analysis of the local evolution of 206 Lagrangian
Volumes (LVs) selected at high redshift around galaxy seeds, identified in a
large-volume cold dark matter (CDM) hydrodynamical
simulation. The LVs have a mass range of . We
follow the dynamical evolution of the density field inside these initially
spherical LVs from up to , witnessing highly
non-linear, anisotropic mass rearrangements within them, leading to the
emergence of the local cosmic web (CW). These mass arrangements have been
analysed in terms of the reduced inertia tensor , focusing on the
evolution of the principal axes of inertia and their corresponding
eigendirections, and paying particular attention to the times when the
evolution of these two structural elements declines. In addition, mass and
component effects along this process have also been investigated. We have found
that deformations are led by dark matter dynamics and they transform most of
the initially spherical LVs into prolate shapes, i.e. filamentary structures.
An analysis of the individual freezing-out time distributions for shapes and
eigendirections shows that first most of the LVs fix their three axes of
symmetry (like a skeleton) early on, while accretion flows towards them still
continue. Very remarkably, we have found that more massive LVs fix their
skeleton earlier on than less massive ones. We briefly discuss the
astrophysical implications our findings could have, including the galaxy
mass-morphology relation and the effects on the galaxy-galaxy merger parameter
space, among others.Comment: 23 pages, 20 figures. Minor editorial improvement
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