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We use two zoom-in $\Lambda$CDM hydrodynamical simulations of massive disk galaxies to study the possible existence of fixed satellite groups showing a kinematically-coherent behaviour across evolution (angular momentum conservation and clustering). We identify three such groups in the two simulations, defining kinematically-coherent, time-persistent planes (KPPs) that last at least from virialization to $z=0$ (more than 7 Gyrs). This proves that orbital pole clustering is not necessarily set in at low redshift, representing a long-lived property of galaxy systems. KPPs are thin and oblate, represent $\sim25-40\%$ of the total number of satellites in the system, and are roughly perpendicular to their corresponding central disk galaxies during certain periods, consistently with Milky Way $z=0$ data. KPP satellite members are statistically distinguishable from satellites outside KPPs: they show higher specific orbital angular momenta, orbit more perpendicularly to the central disk galaxy, and have larger pericentric distances, than the latter. We numerically prove, for the first time, that KPPs and the best-quality positional planes share the same space configuration across time, such that KPPs act as `skeletons' preventing the latter of being washed out in short timescales. In one of the satellite-host systems, we witness the late capture of a massive dwarf galaxy endowed with its own satellite system, also organized into a KPP configuration prior to its capture. We briefly explore the consequences this event has on the host's KPP, and on the possible enhancement of the asymmetry in the number of satellites rotating in one sense or the opposite within the KPP., Comment: 24 pages, 8 figures, 2 tables. Accepted for publication in The Astrophysical Journal

La transformación genética es una técnica atractiva para el mejoramiento de los cítricos ya que evita los largos periodos juveniles y permite introducir nuevas características a un cultivar sin alterar los rasgos existentes. Un paso indispensable para aplicar esta tecnología de mejoramiento de los cítricos, es el desarrollo de sistemas eficientes de transformación genética que confieran ventajas agronómicas. En este reporte se presenta el desarrollo de sistemas de transformación genética basados en Agrobacterium rhizogenes para la toronja (Citrus paradisi cvs. Duncan y Rio Red) y la lima dulce (Citrus limmettioides). Primero se generaron raíces transformadas por medio del cocultivo de segmentos de tallo obtenidos de plántulas germinadas in vitro con A. rhizogenes cepa A4, que contenía el plásmido tipo silvestre pRiA4 y el vector binario pESC4 con los genes nos-nptII y cab-gus. La mayor eficiencia de transformación, medida como el porcentaje de explantes que formaron raíces, se obtuvo en la toronja Duncan (78 %), seguida por la toronja Rio Red (68 %) y la lima dulce (60 %). Se detectó actividad de GUS en 89, 92 y 76 % de las raíces generadas en toronja Duncan, toronja Rio Red y lima dulce, respectivamente. Luego se regeneraron brotes adventicios a través de organogénesis en segmentos de raíz transformada cultivados en medios con citocininas o con citocininas y auxinas; tales brotes adventicios se generaron en 24 % de los casos en toronja Duncan, en 14 % de los de toronja Rio Red y en 8 % de los de lima dulce. Los análisis GUS confirmaron que las plantas regeneradas conservaron la actividad de este gen introducido a las raíces transformadas. Los resultados mostraron que el sistema de transformación establecido introdujo exitosamente ADN foráneo a la toronja y a la lima dulce, y que puede ser útil para la generación de plantas que expresen genes de interés agronómico.

We address the 'plane of satellites problem' by studying planar configurations around two disc galaxies with no late major mergers, formed in zoom-in hydro-simulations. Due to the current lack of good quality kinematic data for M31 satellites, we use only positional information. So far, positional analyses of simulations are unable to find planes as thin and populated as the observed ones. Moreover, they miss systematicity and detail in the plane-searching techniques, as well as in the study of the properties and quality of planes, both in simulations or real data. To fill this gap, i) we extend the 4-galaxy-normal density plot method (Pawlowski et al. 2013) in a way designed to efficiently identify the best quality planes (i.e., thin and populated) without imposing extra constraints on their properties, and ii), we apply it for the first time to simulations. Using zoom-in simulations allows us to mimic MW/M31-like systems regarding the number of satellites involved as well as the galactic disc mass and morphology, in view of possible disc effects. At all timesteps analyzed in both simulations we find satellite planar configurations that are compatible, along given time intervals, with all the spatial characteristics of observed planes identified using the same methodology. However, the fraction of co-orbiting satellites within them is in general low, suggesting time-varying satellite membership. We conclude that high-quality positional planes of satellites are not infrequent in LCDM-formed disc galaxies with a quiet assembly history. Detecting kinematically-coherent, time-persistent planes demands considering the full six-dimensional phase-space information of satellites., Comment: 26 pages, 13 figures, 2 tables. Accepted for publication in ApJ

The red palm weevil (RPW), Rhynchophorus ferrugineus, is one of the worst palm pests worldwide. Our study aims to assess its internal and external morphological response to a sudden but transient decrease in the environmental temperature. Wild pre-pupae were subjected for 7 days to either low (5.0 ± 0.5 °C) or ambient temperature (23 ± 1 °C). Such conditions mimic a thermal anomaly happening in the larval stage most exposed to environmental factors. We quantified the changes undergone at: 1) the internal morphology, by X-Ray Computer Tomography (CT); 2) the 3-D integument’ architecture, by Digital Holographic Microscopy (DHM); and 3) the glucose in hemolymph as a potential endogenous cryoprotectant. From X-ray CT we found that both pre-pupae subjected to cold and those remaining at ambient temperature follow a development where their fat body content decreases while a thick and dense cuticle is formed. There was no difference between both groups in the rate of change of fat body/dense tissues. Nevertheless, the cold group presents a slight developmental delay at the level of hemolymph content. Through DHM we again obtained that pre-pupae subjected to cold have not experienced a stop in their development. However, a more obvious developmental delay is now observed in this group at the level of the integumental roughness. Finally, regarding glucose, we found similar levels in control and ambient temperature larvae, while it was clearly increased in 51,7% of those subjected to cold. Our whole results provide morphological and biochemical evidence showing that the larval-pupal transition of the RPW continues almost undisturbed even during the quiescent state induced by a sudden and severe cold event. Nevertheless, a certain developmental delay is observed in both internal and external morphology. Additionally, the increased glucose level only found in the cold group suggests that glucose is part of the RPW cold tolerance strategy.

Cosmological hydrodynamical simulations show that the baryonic elements that at z = 0 form the stellar populations of late-type galaxies (LTGs), display, at high z, a gaseous web-like organization, where different singular structures (walls, filaments, nodes) show up. The analysis also shows that the spheroid-to-be elements are the first to be involved in the singular structures, while thick and thin disk-to-be elements chronologically follow them. We discuss how these differences at high z can explain the differences among these three components at z = 0.

Cryobanking somatic foetal cells acquire much relevance in endangered species for biodiversity conservation purposes. Such cells could be later used to reintroduce the lost genes into the breeding pool, by inducing pluripotency and/or nuclear transfer if necessary. Since requirements for preserving foetal cells are not always the same as for adult ones, we evaluated the cryosensitivity of foetal skin cells in comparison with adult ones from the critically endangered Iberian lynx. Responses to cryoinjury were analyzed in both thawed cell types by means of cell viability and functionality (by analyzing their membrane integrity, metabolic activity, glycosaminoglycan content and proliferative activity). Freezing media included the permeating cryoprotectant Me 2 SO, either alone or along with the non-permeating cryoprotectant sucrose at 0.1 or 0.2 M. When Me 2 SO was the only cryoprotectant, survival rate fell in thawed foetal cells to 54 ± 4% (against 89 ± 6% for thawed adult ones) and both proliferative and metabolic activities remained significantly lower than values for thawed adult cells. However, the combination of sucrose (both 0.1 as 0.2) and Me 2 SO in foetal cells significantly increased their survival rates (to 71 ± 4% and 73 ± 5%, respectively), proliferative activities (partially at day 7 and completely at day 14 after thawing) and metabolic activities. Our findings clearly show a difference between foetal and adult cells concerning their cryopreservation sensitivity and requirements, as well as their recovery time after thawing. These results are of relevance for the cryopreservation of foetal and adult cells from the Iberian lynx and could be also useful for other mammals.

In this work we present a detailed analysis of the global and fine structure of four middle-mass disc galaxies obtained from hydrodynamic simulations in a Λcold dark matter (ΛCDM) scenario. These objects have photometric disc-to-total ratios in good agreement with those observed for late-type spirals, as well as kinematic properties in agreement with the observational I-band Tully–Fisher relation. We identify the different dynamical components at redshift zero 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 α-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 formed from rapid collapse at early times, and a high-metallicity peak, which could be related to a pseudo-bulge formed from instabilities of the inner disc. The thin disc appears in our simulations as the youngest and most metal-rich component, with median stellar ages ranging from 3.8 to 6.7 Gyr. The radial distribution of ages and colours in this component is U-shaped: the new stars are forming in the inner regions, where the galaxy is bluer, and then migrate through secular processes reaching the outer parts. Finally, we also find in all simulated galaxies a thick disc containing about 16 per cent 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 α-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.

We describe an SPH model for chemical enrichment and radiative cooling in cosmological simulations of structure formation. This model includes: i) the delayed gas restitution from stars by means of a probabilistic approach designed to reduce the statistical noise and, hence, to allow for the study of the inner chemical structure of objects with moderately high numbers of particles; ii) the full dependence of metal production on the detailed chemical composition of stellar particles by using, for the first time in SPH codes, the Qij matrix formalism that relates each nucleosynthetic product to its sources; and iii) the full dependence of radiative cooling on the detailed chemical composition of gas particles, achieved through a fast algorithm using a new metallicity parameter zeta(T) that gives the weight of each element on the total cooling function. The resolution effects and the results obtained from this SPH chemical model have been tested by comparing its predictions in different problems with known theoretical solutions. We also present some preliminary results on the chemical properties of elliptical galaxies found in self-consistent cosmological simulations. Such simulations show that the above zeta-cooling method is important to prevent an overestimation of the metallicity-dependent cooling rate, whereas the Qij formalism is important to prevent a significant underestimation of the [alpha/Fe] ratio in simulated galaxy-like objects., 19 pages, 22 figures, 2 tables; accepted for publication in MNRAS

We report on an extension, through cosmological simulations, of the two-phase formation scenario for elliptical galaxies to classical spiral bulges. In particular, we analyze the possibility that the old stellar population of bulges forms in a fast phase, while the younger stellar component forms or is assembled in a slow phase, in part from disk material suffering instabilities and in part through satellite capture or mergers.

Combined with other CMB experiments, the WMAP survey provides an accurate estimate of the baryon density of the Universe. In the framework of the standard Big Bang Nucleosynthesis (BBN), such a baryon density leads to predictions for the primordial abundances of $^{4}$He and D in good agreement with observations. However, it also leads to a significant discrepancy between the predicted and observed primordial abundance of $^{7}$Li. Such a discrepancy is often termed as 'the lithium problem'. In this paper, we analyze this problem in the framework of scalar-tensor theories of gravity. It is shown that an expansion of the Universe slightly slower than in General Relativity before BBN, but faster during BBN, solves the lithium problem and leads to $^4$He and D primordial abundances consistent with the observational constraints. This kind of behavior is obtained in numerous scalar-tensor models, both with and without a self-interaction potential for the scalar field. In models with a self-interacting scalar field, the convergence towards General Relativity is ensured without any condition, thanks to an attraction mechanism which starts to work during the radiation-dominated epoch.

This paper describes the development of a low-cost mini-robot that is controlled by visual gestures. The prototype allows a person with disabilities to perform visual inspections indoors and in domestic spaces. Such a device could be used as the operator's eyes obviating the need for him to move about. The robot is equipped with a motorised webcam that is also controlled by visual gestures. This camera is used to monitor tasks in the home using the mini-robot while the operator remains quiet and motionless. The prototype was evaluated through several experiments testing the ability to use the mini-robot’s kinematics and communication systems to make it follow certain paths. The mini-robot can be programmed with specific orders and can be tele-operated by means of 3D hand gestures to enable the operator to perform movements and monitor tasks from a distance. The research that yielded these results has received funding from the projects DPI2012-32390 and PROMETEO/2013/085.

Astrophysical Journal Letters 800.2 (2015): L30 reproduced by permission of the AAS, Models of the advanced stages of gravitational instability predict that baryons that form the stellar populations of current galaxies at z = 0 displayed a web-like structure at high z, as part of the cosmic web (CW). We explore details of these predictions using cosmological hydrodynamical simulations. When the stellar populations of the spheroid and disk components of simulated late-type galaxies are traced back separately to high zs we found CW-like structures where spheroid progenitors are more evolved than disk progenitors. The distinction between the corresponding stellar populations, as driven by their specific angular momentum content j, can be explained in terms of the CW evolution, extended to two processes occurring at lower z. First, the spheroid progenitors strongly lose j at collapse, which contrasts with the insignificant j loss of the disk progenitors. The second is related to the lack of alignment, at assembly, between the spheroid-to-be material and the already settled proto-disk, in contrast to the alignment of disk-to-be material, in some cases resulting from circumgalactic, disk-induced gravitational torques. The different final outcomes of these low-z processes have their origins in the different initial conditions driven by the CW dynamics, This work was partially supported by the MICINN and MINECO (Spain) through the grants AYA2009-12792-C03-02, AYA2009-12792-C03-03, and AYA2012-31101 from the PNAyA, as well as by the "Supercomputación y e-Ciencia" Consolider-Ingenio CSD2007-0050 project. A.O. was financially supported through a FPI contract from AYA2009-12792-C03-03 and C.B.B. through a contract from AYA2012-31101

We present results of a study on the evolution of the parameters characterizing the structure and dynamics of the relaxed elliptical-like objects (ELOs) identified at z=0, z=1 and z=1.5 in a set of hydrodynamical, self-consistent simulations operating in the context of a concordance cosmological model. The values of the stellar mass, the stellar half-mass radius and the stellar mean-square velocity have been measured in each ELO and found to populate, at any z, a flattened ellipsoid close to a plane (the dynamical plane, DP). Our simulations indicate that, at the intermediate zs considered, individual ELOs evolve, increasing the values of these parameters as a consequence of on-going mass assembly, but, nevertheless, their DP is roughly preserved within its scatter, in agreement with observations of the Fundamental Plane of ellipticals at different zs. We briefly discuss how this lack of significant dynamical and structural evolution in ELO samples arises, in terms of the two different phases operating in the mass aggregation history of their dark matter halos. According with our simulations, most dissipation involved in ELO formation takes place at the early violent phase, causing the stellar mass, the stellar half-mass radius and the stellar mean-square velocity parameters to settle down to the DP, and, moreover, the transformation of most of the available gas into stars. In the subsequent slow phase, ELO stellar mass growth preferentially occurs through non-dissipative processes, so that the DP is preserved and the ELO star formation rate considerably decreases. These results hint, for the first time, to a possible way of explaining, in the context of cosmological simulations, different apparently paradoxical observational results on ellipticals., 12 pages, 1 figure. Minor changes to match the published version

We present results of a study of the stellar age distributions in the sample of elliptical-like objects (ELOs) identified at z=0 in four simulations operating in the context of a concordance cosmological model. The simulations show that the formation of most stars in each ELO of the sample is a consequence of violent dynamical events, either fast multiclump collapse at high z, or mergers at lower z. This second way can explain the age spread as well as the dynamical peculiarities observed in some ellipticals, but its relative weight is never dominant and decreases as the ELO mass at the halo scale, $M_{vir}$, increases, to such an extent that some recent mergers contributing an important fraction to the total ELO mass can possibly contribute only a small fraction of new born stars. More massive objects have older means and narrower spreads in their stellar age distributions than less massive ones. The ELO sample shows also a tight correlation between $M_{vir}$ and the central stellar l.o.s. velocity dispersion, $\sigma_{los}$. This gives a trend of the means and spreads of ELO stellar populations with $\sigma_{los}$ that is consistent, even quantitatively, with the age effects observationally detected in the stellar populations of elliptical galaxies. Therefore, these effects can be explained as the observational manifestation of the intrinsic correlations found in the ELO sample between $M_{vir}$ and the properties of the stellar age distribution, on the one hand, and $M_{vir}$ and $\sigma_{los}$, on the other hand. These correlations hint, for the first time, at a possible way to reconcile age effects in ellipticals, and, particularly, the increase of $\alpha / $ ratios with $\sigma_{los}$, with the hierarchical clustering paradigm., Comment: 13 pages, 2 figures, accepted for publication in Astrophysical Journal Letters

We report on two fully self-consistent hydrodynamical simulations run, in the context of a ΛCDM cosmological model, with the DEVA code. Galaxy-like-objects of different morphologies form. The assembly patterns identified in these simulations give support to the ab initio scenario to explain morphological differentiation, even if violent events at lower z could also have played a role.

We present a method to detect, in the framework of scalar–tensor gravity theories, the existence of stationary points in the time evolution of the speed-up factor. An attractive aspect of this method is that, once the particular scalar–tensor theory has been specified, the stationary points are found through a simple algebraic equation which does not contain any integration. By applying this method to the three classes of scalar–tensor theories defined by Barrow and Parsons, we have found several new cosmological models with a non-monotonic evolution of the speed-up factor. The physical interest of these models is that, as previously shown by Serna and Alimi, they predict the observed primordial abundance of light elements for a very wide range of baryon density. These models are then consistent with recent CMB and Lyman-α estimates of the baryon content of the universe.

In a previous paper (Serna & Alimi 1996), we have pointed out the existence of some particular scalar-tensor gravity theories able to relax the nucleosynthesis constraint on the cosmic baryonic density. In this paper, we present an exhaustive study of primordial nucleosynthesis in the framework of such theories taking into account the currently adopted observational constraints. We show that a wide class of them allows for a baryonic density very close to that needed for the universe closure. This class of theories converges soon enough towards General Relativity and, hence, is compatible with all solar-system and binary pulsar gravitational tests. In other words, we show that primordial nucleosynthesis does not always impose a very stringent bound on the baryon contribution to the density parameter.

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., Comment: 24 pages, 13 Figures and 6 Tables. Accepted in MNRAS

We present an implementation of hierarchical clustering methods to distribute a set of objects into a set of groups. Our code is particularly conceived to identify and analyze substructures in galaxy clusters or in large-scale catalogues. However, its general scheme allows for very easy adaptation to any other kinds of systems and physical problems. The algorithms to draw the hierarchical tree associated to a given sample of data, as well as those for analyzing and interpreting the results obtained from this technique, are also presented here.

The Astrophysical Journal 763.1 (2013): 26 reproduced by permission of the AAS, 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 inputting low star formation efficiency under the assumption that feedback occurs on subgrid scales, while the GASOLINE simulations have feedback that 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 that 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., This work was partially supported by the MICINN (Spain) through the grants AYA2009-12792-C03-02 and AYA2009-12792-C03-03 from the PNAyA, as well as by the regional Madrid V PRICIT program through the ASTROMADRID network (CAM S2009/ESP-1496) and the “Supercomputación y e-Ciencia” Consolider-Ingenio CSD2007-0050 project.

Astrophysical Journal Letters 732.2 (2011): L32 reproduced by permission of the AAS, 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 z's, 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 of 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., This work was partially supported by the DGES (Spain) through the grants AYA2009-12792-C03-02 and AYA-2009-12792-C03-03, as well as by the ASTROMADRID network (CAM S2009/ESP-1496). A.K. and J.O. were supported by the MICINN, Spain, through the Ramon y Cajal programme and the “Supercomputación y e-Ciencia” Consolider-Ingenio 2010 project (CSD2007-0050), respectively.

An exhaustive study of homogeneous and isotropic cosmological models in the Schmidt-Greiner-Heinz-Mueller (SGHM) theory of gravitation is performed, where present values of dynamical functions are consistent with astronomical observations and solar-system experiments. We find two types of SGHM models: a first class which is exactly equal to the standard general relativistic (GR) cosmological models, and a second class which never reduces to GR. Some analytical and numerical solutions for the second type of SGHM models are then obtained. The age of the Universe predicted by these models is compatible with the age of old globular clusters except for weak bounds on the [Delta][sub 0] parameter defined in this paper.

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., 8 pages, 4 figures. Accepted by ApJL

The baryon density of our Universe, Ωbh2 = 0.0224±0.0009, as inferred from the WMAP first year of observations is used to predict the primordial abundances of light elements produced during Big Bang Nucleosynthesis (BBN). Such a baryon density, and a gravitation described by General Relativity, lead to predictions for the abundances of 4He and D in very good agreement with the observed ones; but they lead to a significant discrepancy between the calculated and the observed 7Li abundances. Supposing that the standard non gravitational sector is not modified, we consider scalar‐tensor theories of gravity, and study their impact on the 7Li abundance. It is shown that solving the lithium problem requires a non trivial behaviour of the expansion rate of the Universe at the epoch of BBN, in order not to violate the constraints from 4He and D. This kind of behaviour is obtained thanks to various models, both without and with self‐interaction for the scalar field.

The baryon density of our Universe, Ωbh2 = 0.0224 ± 0.0009, as inferred from the WMAP first year of observations is used to predict the primordial abundances of light elements produced during Big Bang Nucleosynthesis (BBN). Such a baryon density, and a gravitation described by General Relativity (GR), lead to predictions for the abundances of 4He and D in very good agreement with the observed ones; but they lead to a significant discrepancy between the calculated and the observed 7Li abundances. Supposing that the standard non gravitational sector is not modified, we consider scalar‐tensor theories of gravity, and study their impact on the 7Li abundance. It is shown that solving the lithium problem requires a non trivial behaviour of the expansion rate of the Universe at the epoch of BBN, in order not to violate the constraints from 4He and D.

We present results of an analysis of the properties of spheroid-like galaxies that form in hydrodynamical, self-consistent cosmological simulations run with the DEVA code.

We present results of an analysis of the properties of spheroid-like galaxies that form in hydrodynamical, self-consistent cosmological simulations run with the DEVA code. We find that the structural, dynamical and X-ray properties, as well as their correlations, are compatible with observations of early-type galaxies at low z.

We describe the fundamental patterns of the formation and evolution of an elliptical-like galaxy formed in a self-consistent hydrodynamical simulation run with the DEVA code.

We analyze the structural and dynamical properties of disk-like objects that form in a hydrodynamical, self-consistent cosmological simulation. We show that they are compatible with observations of spiral galaxies.

We study the stability of rotating collisionless self-gravitating spherical systems by using high resolution N-body experiments on a Connection Machine CM-5. We added rotation to Ossipkov-Merritt (hereafter OM) anisotropic spherical systems by using two methods. The first method conserves the anisotropy of the distribution function defined in the OM algorithm. The second method distorts the systems in velocity space. We then show that the stability of systems depends both on their anisotropy and on the value of the ratio between the total kinetic energy and the rotational kinetic energy. We also test the relevance of the stability parameters introduced by Perez et al. (1996) for the case of rotating systems., 15 Pages, 5 Figures, accepted for publication in MNRAS

We have studied the structural and dynamical parameters of two samples of elliptical-like-objects (ELOs) formed in a set of self-consistent hydrodynamical simulations. ELO stellar masses, projected half- stellar mass radii, and stellar central l.o.s. velocity dispersions have been found to define a dynamical Fundamental Plane (FP), whose physical origin we report on.

We present a detailed calculation of the light element production in the framework of Scalar-Tensor (ST) theories of gravitation. The coupling function \omega has been described by an appropriate form which reproduces all the possible asymptotic behaviors at early times of viable ST cosmological models with a monotonic \omega(\Phi). This form gives an exact representation for most of the particular theories proposed in the literature, but also a first-order approximation to many other theories. In most of ST theories, the nucleosynthesis bounds lead to cosmological models which do not significantly differ from the standard FRW ones. We have found however a particular class of ST theories where the expansion rate of the universe during nucleosynthesis can be very different from that found in GR, while the present value of \omega is high enough to ensure compatibility with solar-system experiments. In the framework of this class of theories, right primordial abundances can be obtained for a baryon density range much wider (2.8 \lesssim \eta_{10} \lesssim 58.7) than in GR. Consequently, the usual constraint on the baryon contribution to the density parameter of the universe can be drastically relaxed (0.01 \lesssim \Omega_{b0} \lesssim 1.38) by considering these gravity theories. This is the first time that a ST theory is found to be compatible both with primordial nucleosynthesis and solar-system experiments while implying cosmological models significantly different from the FRW ones., Comment: uuencoded compressed postscript file containing 36 pages, with 8 figures, accepted for publication in Physical Review D

We analyze the qualitative behaviors of scalar-tensor cosmologies with an arbitrary monotonic $\omega(\Phi)$ function. In particular, we are interested on scalar-tensor theories distinguishable at early epochs from General Relativity (GR) but leading to predictions compatible with solar-system experiments. After extending the method developed by Lorentz-Petzold and Barrow, we establish the conditions required for convergence towards GR at $t\rightarrow\infty$. Then, we obtain all the asymptotic analytical solutions at early times which are possible in the framework of these theories. The subsequent qualitative evolution, from these asymptotic solutions until their later convergence towards GR, has been then analyzed by means of numerical computations. From this analysis, we have been able to establish a classification of the different qualitative behaviors of scalar-tensor cosmological models with an arbitrary monotonic $\omega(\Phi)$ function., Comment: uuencoded compressed postscript file containing 41 pages, with 9 figures, accepted for publication in Physical Review D

The mathematical theory of cluster analysis (see, e.g., Andenberg 1973) provides different methods to distribute a set of objects into a set of clusters. We have adapted this method for the founding and the description of (sub)structures in galaxy clusters. An overview of the method is here rapidly described as well as application upon three Abell clusters.

We briefly present some results concerning cosmological implications of scalar-tensor gravity theories. We show that scalar-tensor gravity theories can be a way to relax the primordial nucleosynthesis bound to the baryon density

We present a detailed calculation of light-element production in the Schmidt-Greiner-Heinz-Muller theory of gravitation. The comparison of our results with current observations implies very strong bounds on the allowed deviation from general relativity. These bounds lead to cosmological models which do not significantly differ from the standard Friedmann-Robertson-Walker (FRW) predictions. This result, together with those previously obtained in the literature for other scalar-tensor theories, allows us to conclude that there still does not exist any alternative metric theory of gravitation with a scalar field leading to a viable cosmological evolution distinguishable from the standard FRW one

We use a set of hydrodynamical, self consistent simulations operating in the context of a concordance cosmological model where relaxed elliptical-like objects (ELOs) were identified at different redshifts. ELOs at different redshift are well described by the Sérsic (1968) function. We also obtain a good comparison with observational scaling relations. These results indicate that ELOs conform a homogeneous population at any redshift, except that high z ELOs tend to be more compact that their lower z counterparts. Also, scaling relations point to the rupture of the structural homology.

A thorough calculation of light-element production in Brans-Dicke cosmologies is presented, by taking into account the most general class of these models. The comparison of the outputs of our calculation with current observational data results in bounds on the allowed ω-values. It is found that cosmological models where (dφ/dt) R 3 → C ¬=; 0 when R → 0 and high values of the expansion rate of the universe are ruled out by the primordial nucleosynthesis test. However, if C = 0, light-element production imposes less restrictive bounds on the parameter ω than the experiments in the weak field limit

Reproducing the planes of co-orbiting satellites observed in the MW and M31 so far has represented a challenge for cosmological simulations. We have developed a new method to search for kinematically-coherent groups of satellites and applied it to 2 different cosmological hydro-simulations of disc galaxies. In each simulation we have found such a group, that represents roughly half of the total satellite population and is distributed on a fairly thin plane that persists in time. These results are compatible with the MW and M31 observed planes.