116 research outputs found
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
Massive Galaxies at High-z: Assembly Patterns, Structure & Dynamics in the Fast Phase of Galaxy Formation
Relaxed, massive galactic objects have been identified at redshifts z = 4;5;
and 6 in hydrodynamical simulations run in a large cosmological volume. This
allowed us to analyze the assembly patterns of the high mass end of the galaxy
distribution at these high zs, by focusing on their structural and dynamical
properties. Our simulations indicate that massive objects at high redshift
already follow certain scaling relations. These relations define virial planes
at the halo scale, whereas at the galactic scale they define intrinsic
dynamical planes that are, however, tilted relative to the virial plane.
Therefore, we predict that massive galaxies must lie on fundamental planes from
their formation.
We briefly discuss the physical origin of the tilt in terms the physical
processes underlying massive galaxy formation at high z, in the context of a
two-phase galaxy formation scenario. Specifically, we have found that it lies
on the different behavior of the gravitationally heated gas as compared with
cold gas previously involved in caustic formation, and the mass dependence of
the energy available to heat the gas.Comment: 12 pages, 1 figure. Accepted to Astrophysical Journal Letter
Measuring galaxy segregation using the mark connection function
(abridged) The clustering properties of galaxies belonging to different
luminosity ranges or having different morphological types are different. These
characteristics or `marks' permit to understand the galaxy catalogs that carry
all this information as realizations of marked point processes. Many attempts
have been presented to quantify the dependence of the clustering of galaxies on
their inner properties. The present paper summarizes methods on spatial marked
statistics used in cosmology to disentangle luminosity, colour or morphological
segregation and introduces a new one in this context, the mark connection
function. The methods used here are the partial correlation functions,
including the cross-correlation function, the normalised mark correlation
function, the mark variogram and the mark connection function. All these
methods are applied to a volume-limited sample drawn from the 2dFGRS, using the
spectral type as the mark. We show the virtues of each method to provide
information about the clustering properties of each population, the dependence
of the clustering on the marks, the similarity of the marks as a function of
the pair distances, and the way to characterise the spatial correlation between
the marks. We demonstrate by means of these statistics that passive galaxies
exhibit stronger spatial correlation than active galaxies at small scales (r
<20 Mpc/h). The mark connection function, introduced here, is particularly
useful for understanding the spatial correlation between the marks.Comment: 6 pages, 5 figures, accepted for publication in Astronomy and
Astrophysic
The distribution of mass components in simulated disc galaxies
Using 22 hydrodynamical simulated galaxies in a LCDM cosmological context we
recover not only the observed baryonic Tully-Fisher relation, but also the
observed "mass discrepancy--acceleration" relation, which reflects the
distribution of the main components of the galaxies throughout their disks.
This implies that the simulations, which span the range 52 < V <
222 km/s where V is the circular velocity at the flat part of the
rotation curve, and match galaxy scaling relations, are able to recover the
observed relations between the distributions of stars, gas and dark matter over
the radial range for which we have observational rotation curve data.
Furthermore, we explicitly match the observed baryonic to halo mass relation
for the first time with simulated galaxies. We discuss our results in the
context of the baryon cycle that is inherent in these simulations, and with
regards to the effect of baryonic processes on the distribution of dark matter.Comment: 8 pages, 7 pdf figures. Accepted for publication in MNRAS on 2015
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