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Search Results: 1 - 10 of 227190 matches for " R. Domínguez-Tenreiro "
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Dark Matter Halo Structure in CDM Hydrodynamical Simulations
P. B. Tissera,R. Dom\ci nguez-Tenreiro
Physics , 1998, DOI: 10.1046/j.1365-8711.1998.01440.x
Abstract: 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 $[150-200] km s^{-1}$ 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.
Dynamical Friction for Compound Bodies
R. Domínguez-Tenreiro,M. A. Gómez-Flechoso
Physics , 1997, DOI: 10.1046/j.1365-8711.1998.01224.x
Abstract: In the framework of the fluctuation-dissipation approach to dynamical friction, we derive an expression giving the orbital energy exchange experienced by a compound body as it moves interacting with a non homogeneous discrete background. The body is assumed to be composed of particles endowed with a velocity spectrum and with a non homogeneous spatial distribution. The Chandrasekhar formula is recovered in the limit of a point-like satellite with zero velocity dispersion and infinite temperature moving through an homogeneous infinite medium. In this same limit, but dropping the zero satellite velocity dispersion ($\sigma_S$) condition, the orbital energy loss is found to be smaller than in the $\sigma_S=0$ case by a factor of up to an order of magnitude in some situations.
Lagrangian Volume Deformations around Simulated Galaxies
S. Robles,R. Domínguez-Tenreiro,J. O?orbe,F. J. Martínez-Serrano
Physics , 2015, DOI: 10.1093/mnras/stv820
Abstract: 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 $\Lambda$ cold dark matter ($\Lambda$CDM) hydrodynamical simulation. The LVs have a mass range of $1 - 1500 \times 10^{10} M_\odot$. We follow the dynamical evolution of the density field inside these initially spherical LVs from $z=10$ up to $z_{\rm low} = 0.05$, 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 $I_{ij}^r$, 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.
Large-Scale Gas Dynamics in the Adhesion Model: Implications for the Two-Phase Massive Galaxy Formation Scenario
R. Domínguez-Tenreiro,J. O?orbe,F. Martínez-Serrano,A. Serna
Physics , 2010, DOI: 10.1111/j.1365-2966.2011.18379.x
Abstract: The mass assembly and star formation histories of massive galaxies identified at low redshift z in different cosmological hydrodynamical simulations, have been studied through a detailed follow-up backwards in time of their constituent mass elements (sampled by particles) of different types. Then, the configurations they depict at progressively higher zs have been analysed. The analyses show that these histories share common generic patterns, irrespective of particular circumstances. In any case, the results we have found are different depending on the particle type. The most outstanding differences follow. We have found that by z ~ 3.5 - 6, mass elements identified as stellar particles at z=0 exhibit a gaseous cosmic-web-like morphology with scales of ~ 1 physical Mpc, where the densest mass elements have already turned into stars by z ~ 6. These settings are in fact the densest pieces of the cosmic web, where no hot particles show up, and dynamically organized as a hierarchy of flow convergence regions, that is, attraction basins for mass flows. On the other hand, mass elements identified at the diffuse hot coronae surrounding massive galaxies at z = 0, do not display a clear web-like morphology at any z. Diffuse gas is heated when flow convergence regions go through contractive deformations, and most of it keeps hot and with low density along the evolution. To shed light on the physical foundations of the behaviour our analyses show up, as well as on their possible observational implications, these patterns have been confronted with some generic properties of singular flows as described by the adhesion model. We have found that these common patterns simulations show can be interpreted as a consequence of flow properties, that, moreover, could explain different generic observational results on massive galaxies or their samples. We briefly discuss some of them.[Abridged]
The Main Sequence and the Fundamental Metallicity Relation in MaGICC Galaxies: Evolution and Scatter
A. Obreja,C. B. Brook,G. Stinson,R. Domínguez-Tenreiro,B. K. Gibson,L. Silva,G. L. Granato
Physics , 2014, DOI: 10.1093/mnras/stu891
Abstract: Using cosmological galaxy simulations from the MaGICC project, we study the evolution of the stellar masses, star formation rates and gas phase abundances of star forming galaxies. We derive the stellar masses and star formation rates using observational relations based on spectral energy distributions by applying the new radiative transfer code GRASIL-3D to our simulated galaxies. The simulations match well the evolution of the stellar mass-halo mass relation, have a star forming main sequence that maintains a constant slope out to redshift z $\sim$ 2, and populate projections of the stellar mass - star formation - metallicity plane, similar to observed star forming disc galaxies. We discuss small differences between these projections in observational data and in simulations, and the possible causes for the discrepancies. The light-weighted stellar masses are in good agreement with the simulation values, the differences between the two varying between 0.06 dex and 0.20 dex. We also find a good agreement between the star formation rate tracer and the true (time-averaged) simulation star formation rates. Regardless if we use mass- or light-weighted quantities, our simulations indicate that bursty star formation cycles can account for the scatter in the star forming main sequence.
Massive Galaxies at High-z: Assembly Patterns, Structure & Dynamics in the Fast Phase of Galaxy Formation
J. O?orbe,F. J. Martínez-Serrano,R. Domínguez-Tenreiro,A. Knebe,A. Serna
Physics , 2011, DOI: 10.1088/2041-8205/732/2/L32
Abstract: 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.
A two-phase scenario for bulge assembly in LCDM cosmologies
A. Obreja,R. Domínguez-Tenreiro,C. Brook,F. J. Martínez-Serrano,M. Doménech-Moral,A. Serna,M. Mollá,G. Stinson
Physics , 2012, DOI: 10.1088/0004-637X/763/1/26
Abstract: We analyze and compare the bulges of a sample of L* spiral galaxies in hydrodynamical simulations in a cosmological context, using two different codes, P-DEVA and GASOLINE. The codes regulate star formation in very different ways, with P-DEVA simulations inputing low star formation efficiency under the assumption that feedback occurs on subgrid scales, while the GASOLINE simulations have feedback which drives large scale outflows. In all cases, the marked knee-shape in mass aggregation tracks, corresponding to the transition from an early phase of rapid mass assembly to a later slower one, separates the properties of two populations within the simulated bulges. The bulges analyzed show an important early starburst resulting from the collapse-like fast phase of mass assembly, followed by a second phase with lower star formation, driven by a variety of processes such as disk instabilities and/or mergers. Classifying bulge stellar particles identified at z=0 into old and young according to these two phases, we found bulge stellar sub-populations with distinct kinematics, shapes, stellar ages and metal contents. The young components are more oblate, generally smaller, more rotationally supported, with higher metallicity and less alpha-element enhanced than the old ones. These results are consistent with the current observational status of bulges, and provide an explanation for some apparently paradoxical observations, such as bulge rejuvenation and metal-content gradients observed. Our results suggest that bulges of L* galaxies will generically have two bulge populations which can be likened to classical and pseudo-bulges, with differences being in the relative proportions of the two, which may vary due to galaxy mass and specific mass accretion and merger histories.
GRASIL-3D: an Implemention of Dust Effects in the SEDs of Simulated Galaxies
R. Domínguez-Tenreiro,A. Obreja,G. L. Granato,A. Schurer,P. Alpresa,L. Silva,C. B. Brook,A. Serna
Physics , 2013, DOI: 10.1093/mnras/stu240
Abstract: We introduce a new model for the spectral energy distribution of galaxies, GRASIL-3D, which includes a careful modelling of the dust component of the interstellar medium. GRASIL-3D is an entirely new model based on the formalism of an existing and widely applied spectrophotometric model, GRASIL, but specifically designed to be interfaced with galaxies with any arbitrarily given geometry, such as galaxies calculated by theoretical hydrodynamical galaxy formation codes. GRASIL-3D is designed to separately treat radiative transfer in molecular clouds and in the diffuse cirrus component. The code has a general applicability to the outputs of simulated galaxies, either from Lagrangian or Eulerian hydrodynamic codes. As an application, the new model has been interfaced to the P-DEVA and GASOLINE smoothed-particle hydrodynamic codes, and has been used to calculate the spectral energy distribution for a variety of simulated galaxies from UV to sub-millimeter wavelengths, whose comparison with observational data gives encouraging results. In addition, GRASIL-3D allows 2D images of such galaxies to be obtained, at several angles and in different bands.
Disk galaxies with broken luminosity profiles from cosmological simulations
Francisco J. Martínez-Serrano,Arturo Serna,Mariola Doménech-Moral,Rosa Domínguez-Tenreiro
Physics , 2009, DOI: 10.1088/0004-637X/705/2/L133
Abstract: We present SPH cosmological simulations of the formation of three disk galaxies with a detailed treatment of chemical evolution and cooling. The resulting galaxies have properties compatible with observations: relatively high disk-to-total ratios, thin stellar disks and good agreement with the Tully-Fisher and the luminosity-size relations. They present a break in the luminosity profile at 3.0 +- 0.5 disk scale lengths, while showing an exponential mass profile without any apparent breaks, in line with recent observational results. Since the stellar mass profile is exponential, only differences in the stellar populations can be the cause of the luminosity break. Although we find a cutoff for the star formation rate imposed by a density threshold in our star formation model, it does not coincide with the luminosity break and is located at 4.3 +- 0.4 disk scale lengths, with star formation going on between both radii. The color profiles and the age profiles are "U-shaped", with the minimum for both profiles located approximately at the break radius. The SFR to stellar mass ratio increases until the break, explaining the coincidence of the break with the minimum of the age profile. Beyond the break we find a steep decline in the gas density and, consequently, a decline in the SFR and redder colors. We show that most stars (64-78%) in the outer disk originate in the inner disk and afterwards migrate there. Such stellar migrations are likely the main origin of the U-shaped age profile and, therefore, of the luminosity break.
Formation of galaxies in ΛCDM cosmologies. I. The fine structure of disc galaxies
Mariola Doménech-Moral,Francisco J. Martínez-Serrano,Rosa Domínguez-Tenreiro,Arturo Serna
Physics , 2012, DOI: 10.1111/j.1365-2966.2012.20534.x
Abstract: We present a detailed analysis of the global and fine structure of four middle-mass disc galaxies obtained from simulations in a $\Lambda$CDM scenario. These objects have photometric D/T ratios in good agreement with those observed for late-type spirals, as well as kinematic properties in agreement with the observational Tully-Fisher relation. We identify the different dynamical components at z=0 on the basis of both orbital parameters and the binding energy of stars in the galaxy. In this way, we recognize a slowly rotating centrally concentrated spheroid, and two disc components supported by rotation: a thin disc with stars in nearly circular orbits, and a thick disc with orbital parameters transitional between the thin disc and the spheroid. The spheroidal component is composed mainly by old, metal-poor and {\alpha}-enhanced stars. The distribution of metals in this component shows, however, a clear bimodality with a low-metallicity peak, which could be related to a classical bulge, and a high-metallicity peak, which could be related to a pseudo-bulge. The thin disc appears in our simulations as the youngest and most metal-rich component. The radial distribution of ages and colours in this component are U-shaped: the new stars are forming in the inner regions, and then migrate through secular processes. Finally, we also find a thick disc containing about 16% of the total stellar mass and with properties that are intermediate between those of the thin disc and the spheroid. Its low-metallicity stars are {\alpha}-enhanced when compared to thin disc stars of the same metallicity. The structural parameters (e.g., the scale height) of the simulated thick discs suggest that such a component could result from the combination of different thickening mechanisms that include merger-driven processes, but also long-lived internal perturbations of the thin disc. [Abridged]
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