arXiv subjects

Hector Aceves

Publications and source records attributed to Hector Aceves.

25 records · Page 2Linked to original sources

arXiv2005

Preservation of Cuspy Profiles in Disk Galaxy Mergers

We carried out three self-consistent $N$-body simulations of galaxy mergers, with a cuspy dark matter profile, in order to study if the inner dark density slope is preserved in the remnants. In these simulations the progenitors include both a stellar disk and an intrinsic angular momentum for the halos, unlike previous similar studies. The mass-ratios of progenitor galaxies are about 1:1, 1:3 and 1:10. We find that the initial cuspy density profile of the dark halos is preserved in the remnants for the cases considered here.

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arXiv2005

From the Tully-Fisher relation to the Fundamental Plane through Mergers

We set up a series of self-consistent N-body simulations to investigate the fundamental plane of merger remnants of spiral galaxies. These last ones are obtained from a theoretical Tully-Fisher relation at z=1, assuming a constant mass-to-light ratio within the LambdaCDM cosmogony. Using a Sersic growth curve and an orthogonal fitting method, we found that the fundamental plane of our merger remnants is described by the relation Re ~ sigma^{1.48} Ie^{-0.75} which is in good agreement with that reported from the Sloan Digital Sky Survey Re ~ sigma^{1.49} Ie^{-0.75}. However, the R^{1/4}-profile leads to a fundamental plane given by Re ~ sigma^{1.79} Ie^{-0.60}. In general, the correlation found in our merger remnants arises from homology breaking (V^2 ~ sigma^nu, Rg ~ Re^eta) in combination with a mass scaling relation between the total and luminous mass, $M ~ ML^gamma. Considering an orthogonal fitting method, it is found that 1.74<nu<1.79, 0.21<eta<0.52 and 0.80<gamma<0.90 depending on the adopted profile (Sersic or R^{1/4}).

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arXiv2002

N-Body Simulations of Small Galaxy Groups

A series of N-body simulations aimed to study the dynamics of small groups of galaxies are presented. The properties of small galaxy groups are very well reproduced, and those of Hickson's compact groups are well reproduced by the most advanced stage of collapsing groups. We find no overmerging problem in our simulations. An important fraction of groups (~40%) initially in virial equilibrium can last for ~10 Gyr without complete merging. These results provide an alternative solution to the overmerging expected in Hicksons's compact groups.

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arXiv2001

Dynamical Evolution of Triplets of Galaxies

By means of N-body simulations we study the global dynamics of triplets of galaxies, considering initial conditions starting from `maximum expansion' and in virial equilibrium. Unlike previous studies we treat galaxies self-consistently. We do not consider the influence of a primordial common halo of dark matter. Our results indicate that a low number of triple mergers are expected at the present epoch (~10%) for collapsing triplets. Initially virialised conditions yield ~5% of triple mergers in ~10 Gyr of evolution; hence, the 3-galaxy problem has stable states. No overmerging problem for these small groups of galaxies is found. Their geometrical properties, as reflected by the Agekyan-Anosova map, do not show an excess of extreme hierarchical triplets. The median velocity dispersion of observed compact triplets (~100 km/s) is not well reproduced in our models at the present epoch. However, about 10% of simulated triplets starting from maximum expansion have dynamical properties very similar to them. Our median values agree, however, very well with new data on triples. We find that the median mass estimators performs somewhat better than the virial mass estimate. The VME underestimates mass by \~35%. We conclude that Karachentsev's compact triplets probably represent the most advanced stage of gravitational clustering of initially diffuse triplets.

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arXiv1999

Triplets of Galaxies: Some Dynamical Aspects

We present a study of the dynamics of triplets of galaxies. In particular we focus on properties that are directly comparable with observations: e.g., velocity dispersion, mean harmonic radius, and virial mass. We find, for example, that the median velocity dispersion of our simulations is smaller (<50 km/s) than the observed value (~100 km/s). A possible solution to this discrepancy is to consider triplets as non-isolated systems; e.g. subject to a tidal perturbation from a poor cluster in a Hubble time. We suggest that the dynamics of triplets is intimately linked to the large-scale structure, and evolution, of the universe.

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arXiv1999

A Numerical Experiment of a Triple Merger of Spirals

We present a preliminary report on the dynamical evolution of triplets of spiral galaxies that lead to merger remnants that resemble an elliptical. We find that large projected stellar tidal tails ~200 Kpc can develop during the binary formation, and up to ~350 Kpc in the third galaxy when this merges with the binary. When gas is treated as test-particles, gaseous tidal tails may reach up to ~ 1 Mpc in radius in a Hubble time; this radius is similar to the size of the common dark halo formed during the interaction. It is suggested that gaseous tails may provide a mean to determine to some extent the size of the common dark halo formed during the merging of spirals. The stellar remnant shows an elliptical-like surface density profile, but its phase-space retains more information that can be used to determine whether it was assembled from spirals or not.

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arXiv1999

Estimating Masses in Clusters of Galaxies

The projected (PME) and virial mass estimator (VME) are revisited and tested using an N-body equilibrium system. It is found that the PME can overestimate the mass by approx 40% if a cluster is sampled only about its effective radius, Re. The exact value of this error depends on the mass profile of the cluster. The VME can yield errors of approx 20% if we are also able to sample about one Re. Both estimators yield the correct total mass for an equilibrium system. Theoretically, if we know the total extent of the system, the VME provides an accurate mass at different radii provided its gravitational potential term is correctly taken into consideration. The VME can provide acceptable masses for equilibrium systems with anisotropic velocity dispersions.

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