arXiv subjects

Gastão B. Lima Neto

Publications and source records attributed to Gastão B. Lima Neto.

17 recordsLinked to original sources

arXiv2026

Satellite compaction pathways: environmental drivers shaping dwarf galaxy corpulence in the TNG50 simulation

We explore the physical mechanisms driving dwarf galaxy corpulence, focusing on those that end up as compact satellites. We select dwarf galaxies at $z=0$ with $\log(M_\star/{\rm M}_\odot)$ between 8.4 and 9.2 from the TNG50 hydrodynamical simulation after excluding systems flagged as potentially spurious. Compact dwarfs are defined according to the $z=0$ size-mass relation as those on the lower envelope of its main branch or on its lower-size secondary branch, while "Normal" lie on the main branch spine. We identify two robust compaction pathways and a third, more tentative, channel: 1) Compact satellites that remain rich in dark matter (DM) inhabit poorer environments having fewer mergers, favouring the accretion of lower-angular-momentum gas. This allows gas inflows that drive concentrated inner star formation and compaction, as previously found for centrals. 2) Most DM-poor satellites (which typically end up red and metal-rich for their stellar mass) undergo compaction mainly caused by tidal stripping of outer stars. Their compaction is faster when gas is present, by at least 15 per cent after correcting for the stronger tidal field. 3) For most of our few very metal-rich DM-poor Compact satellites, the major compaction phase begins with a starburst driven by ram pressure compression near first pericentre, even if much of the compaction often occurs during subsequent tidal stripping. As a result, compact dwarf satellites in TNG50 arise through distinct pathways. We discuss how numerical effects can affect this conclusion.

astro-ph.GA↗

arXiv2026

Simulations of collision and sloshing in the galaxy group NGC 5098/5096

The study of galaxy groups is essential to understanding the evolutionary history of large-scale structures in the Universe. These dense environments have a significant impact on galaxy evolution, influencing their gas content, morphology, and star formation activity. In this work we analyse in detail the system NGC~5098$/$5096 composed of two galaxy groups. We performed hydrodynamical $N$-body simulations of a galaxy group collision aimed at reproducing the gas sloshing and surface brightness distribution observed in X-ray data. We conducted a detailed X-ray analysis and generated mock image \textit{Chandra} observations from our simulations. The resulting corrected mock image surface brightness profiles show good agreement with the observed data. The relative line-of-sight velocity between NGC~5098 and NGC~5096 is $v_{\mathrm{los}} = 700$ km s$^{-1}$, with a projected separation of $d_{\mathrm{proj}} = 155$ kpc, suggesting that the collision occurs nearly in the line-of-sight. Our simulations were performed with an inclination angle of $80^\circ$ in order to reproduce the dynamical constraints. We also find a correlation between the dark matter and intragroup light distributions when comparing the residual dark matter map with the intragroup light morphology. Our best-fitting model is consistent with these observational constraints and provides a plausible dynamical scenario for the current state of the NGC~5098 group interaction with NGC 5096.

astro-ph.GA↗

arXiv2024

What drives the corpulence of galaxies? I. The formation of central compact dwarf galaxies in TNG50

Nearby dwarf galaxies display a variety of effective radii (sizes) at a given stellar mass, suggesting different evolution scenarios according to their final "stellar" size. The TNG hydrodynamical simulations present a bimodality in the z = 0 size - mass relation (SMRz0) of dwarf galaxies, at $r_{1/2,\star}$ ~ 450 pc. Using the TNG50 simulation, we explored the evolution of the most massive progenitors of dwarf galaxies (z=0 $\log( M_\star / \mathrm{M}_\odot)$ between 8.4 and 9.2) that end up as central galaxies of their groups. We split these dwarfs into three classes of the SMRz0: "Normals" from the central spine of the main branch, and "Compacts" from the secondary branch as well as the lower envelope of the main branch. Both classes of Compacts see their stellar sizes decrease from z ~ 1 onwards in contrast to Normals, while the sizes of the gas and dark matter (DM) components continue to increase (as for Normals). A detailed analysis reveals that Compacts live in poorer environments, and thus suffer fewer major mergers from z = 0.8 onwards, which otherwise would pump angular momentum into the gas, allowing strong gas inflows, producing inner star formation, and thus leading to the buildup of a stellar core. Compacts are predicted to be rounder and to have bluer cores. Compact dwarfs of similar sizes are observed in the GAMA survey, but the bimodality in size is less evident and the most compact dwarfs tend to be passive rather than star forming, as in TNG50. Our conclusions should therefore be confirmed with future cosmological hydrodynamical simulations.

astro-ph.GA↗

arXiv2024

Simulating the arrival of the southern substructure in the galaxy cluster Abell 1758

Abell 1758 (z~0.278) is a galaxy cluster composed of two structures: A1758N and A1758S, separated by ~2.2 Mpc. The northern cluster is itself a dissociative merging cluster that has already been modelled by dedicated simulations. Recent radio observations revealed the existence of a previously undetected bridge connecting A1758N and A1758S. New simulations are now needed to take into account the presence of A1758S. We wish to evaluate which orbital configuration would be compatible with a bridge between the clusters. Using N-body hydrodynamical simulations that build upon the previous model, we explore different scenarios that could have led to the current observed configuration. Five types of orbital approaches were tested: radial, tangential, vertical, post-apocentric, and outgoing. We found that the incoming simulated scenarios are generally consistent with mild enhancements of gas density between the approaching clusters. The mock X-ray images exhibit a detectable bridge in all cases. Compared to measurements of Chandra data, the amplitude of the X-ray excess is overestimated by a factor of ~2--3 in the best simulations. The scenario of tangential approach proved to be the one that best matches the properties of the profiles of X-ray surface brightness. The scenarios of radial approach of vertical approach are also marginally compatible.

astro-ph.CO↗

arXiv2020

Theoretical clues about dust accumulation and galaxy obscuration at high and low redshift

Since the epoch of cosmic star formation peak at $z \sim 2$, most of it is obscured in high mass galaxies, while in low mass galaxies the radiation escapes unobstructed. During the reionization epoch, the presence of evolved, dust obscured galaxies are a challenge to galaxy formation and evolution models. By means of a chemodynamical evolution model, we investigate the star formation and dust production required to build up the bulk of dust in galaxies with initial baryonic mass ranging from $7.5 \times 10^{7}$~M$_\odot$ to $2.0 \times 10^{12}$~M$_\odot$. The star formation efficiency was also chosen to represent the star formation rate from irregular dwarf to giant elliptical galaxies. We adopted a dust coagulation efficiency from \citep[][Case A]{dwek1998evolution} as well as a lower efficiency one (Case B), about five times smaller than Case A. All possible combination of these parameters was computed, summing forty different scenarios. We find that in high stellar formation systems the dust accretion in ISM rules over stellar production before the star formation peak, making these systems almost insensible to dust coagulation efficiency. In low star formation systems, the difference between Case A and B lasts longer, mainly in small galaxies. Thus, small irregular galaxies should be the best place to discriminate different dust sources. In our observational sample, taken from the literature, dust-to-gas ratio tends to be more spread only than dust mass, for both stellar mass and star formation rate. Dust-to-gas vs. dust-to-star diagram is a good tracer for both galaxy and dust evolution, due to the link between gas, star, dust and star formation rate. However, the model do not constrain simultaneously all this quantities. The new generation facilities (such as JWST, ELT, VLT and SPICA) will be indispensable to constrain dust formation across the cosmic time.

astro-ph.GA↗

arXiv2018

Galaxy cluster mergers as triggers for the formation of jellyfish galaxies: case study of the A901/2 system

The A901/2 system is a rare case of galaxy cluster interaction, in which two galaxy clusters and two smaller groups are seen in route of collision with each other simultaneously. Within each of the four substructures, several galaxies with features indicative of jellyfish morphologies have been observed. In this paper, we propose a hydrodynamic model for the merger as a whole, compatible with its diffuse X-ray emission, and correlate the gas properties in this model with the locations of the jellyfish galaxy candidates in the real system. We find that jellyfish galaxies seem to be preferentially located near a boundary inside each subcluster where diffuse gas moving along with the subcluster and diffuse gas from the remainder of the system meet. The velocity change in those boundaries is such that a factor of up to $\sim$1000 increase in the ram pressure takes place within a few hundred kpc, which could trigger the high rate of gas loss necessary for a jellyfish morphology to emerge. A theoretical treatment of ram pressure stripping in the environment of galaxy cluster mergers has not been presented in the literature so far; we propose that this could be a common scenario for the formation of jellyfish morphologies in such systems.

astro-ph.GA↗

arXiv2018

New observational constraints on interacting dark energy using galaxy clusters virial equilibrium states

As the dark sector remains unknown in composition and interaction between dark energy and dark matter stand out as natural, observations of galaxy clusters out of equilibrium abound, opening a promising window on these questions. We continue here the exploration of dark sector interaction detection via clusters virial equilibrium state for all clusters configurations. The dynamics of clusters is evaluated with the Layzer-Irvine equation, a simple model of an interacting dark sector and some simplifying assumptions to obtain the time-dependent part of the virial dynamics. The clusters' data are concentrated in optical weak lensing and X-ray observations that evaluate, respectively, the clusters' mass profiles and temperatures. The global inconsistency of available X-ray data led us to constitute `gold' cluster samples. Through a Bayesian analysis, they are processed to obtain consistent interaction detected up to 3$σ$, in compounded interaction strength for 11 clusters at $-0.027 \pm 0.009$ that translate in compounded universal equilibrium virial ratio of $-0.61^{+0.04}_{-0.03}$. The level of detection and inconsistency of X-ray data call for caution, although future instruments promise a clearer detection soon.

astro-ph.CO↗

arXiv2018

Free-floating molecular clumps and gas mixing: hydrodynamic aftermaths of the intracluster$-$interstellar medium interaction

The interaction of gas-rich galaxies with the intra-cluster medium (ICM) of galaxy clusters has a remarkable impact on their evolution, mainly due to the gas loss associated with this process. In this work, we use an idealised, high-resolution simulation of a Virgo-like cluster, run with RAMSES and with dynamics reproducing that of a zoom cosmological simulation, to investigate the interaction of infalling galaxies with the ICM. We find that the tails of ram pressure stripped galaxies give rise to a population of up to more than a hundred clumps of molecular gas lurking in the cluster. The number count of those clumps varies a lot over time -- they are preferably generated when a large galaxy crosses the cluster (M$_{200c} > 10^{12}$ M$_\odot$), and their lifetime ($\lesssim 300$ Myr) is small compared to the age of the cluster. We compute the intracluster luminosity associated with the star formation which takes place within those clumps, finding that the stars formed in all of the galaxy tails combined amount to an irrelevant contribution to the intracluster light. Surprisingly, we also find in our simulation that the ICM gas significantly changes the composition of the gaseous disks of the galaxies: after crossing the cluster once, typically 20% of the cold gas still in those disks comes from the ICM.

astro-ph.GA↗

arXiv2017

Properties of the circumgalactic medium in simulations compared to observations

Galaxies are surrounded by extended gaseous halos which store significant fractions of chemical elements. These are syntethized by the stellar populations and later ejected into the circumgalactic medium (CGM) by different mechanism, of which supernova feedback is considered one of the most relevant. We explore the properties of this metal reservoir surrounding star-forming galaxies in a cosmological context aiming to investigate the chemical loop between galaxies and their CGM, and the ability of the subgrid models to reproduce observational results. Using cosmological hydrodynamical simulations, we analyse the gas-phase chemical contents of galaxies with stellar masses in the range $10^{9} - 10^{11}\,{\rm M}_{\odot}$. We estimate the fractions of metals stored in the different CGM phases, and the predicted OVI and SiIII column densities within the virial radius. We find roughly $10^{7}\,{\rm M}_{\odot}$ of oxygen in the CGM of simulated galaxies having $M_{\star}{\sim}10^{10}\,{\rm M}_{\odot}$, in fair agreement with the lower limits imposed by observations. The $M_{\rm oxy}$ is found to correlate with $M_{\star}$, at odds with current observational trends but in agreement with other numerical results. The estimated profiles of OVI column density reveal a substantial shortage of that ion, whereas SiIII, which probes the cool phase, is overpredicted. The analysis of the relative contributions of both ions from the hot, warm and cool phases suggests that the warm gas ($ 10^5~{\rm K} < T < 10^6~{\rm K}$) should be more abundant in order to bridge the mismatch with the observations, or alternatively, that more metals should be stored in this gas-phase. Adittionally, we find that the X-ray coronae around the simulated galaxies have luminosities and temperatures in decent agreement with the available observational estimates. [abridged]

astro-ph.GA↗

arXiv2017

Weak lensing and spectroscopic analysis of the nearby dissociative merging galaxy cluster Abell 3376

The galaxy cluster Abell~3376 is a nearby (z=0.046) dissociative merging cluster surrounded by two prominent radio relics and showing an X-ray comet-like morphology. The merger system is comprised of the subclusters A3376W & A3376E. Based on new deep multi-wavelength large-field images and published redshifts, we bring new insights about the history of this merger. Despite the difficulty of applying the weak lensing technique at such low redshift, we successfully recovered the mass distribution in the cluster field. Moreover, with the application of a two-body model, we have addressed the dynamics of these merging system. We have found the individual masses of M_{200}^{W}=3.0_{-1.7}^{+1.3}x10^{14} M_{\odot} and M_{200}^{E}=0.9_{-0.8}^{+0.5}x10^{14} M_{\odot}. The cometary shaped X-ray distribution shows only one peak spatially coincident with both Eastern BCG and the A3376E mass peak whereas the gas content of A3376W seems to be stripped out. Our data allowed us to confirm the existence of a third subcluster located at the North, 1147+-62 kpc apart from the neighbour subcluster A3376E and having a mass M_{200}^{N}=1.4_{-1.0}^{+0.7}x10^{14} M_{\odot}. From our dynamical analysis, we found the merging is taking place very close to the plane of the sky, with the merger axis just 10 deg +-11 deg from it. The application of a two-body analysis code showed that the merging cluster is seen 0.9_{-0.3}^{+0.2} Gyr after the pericentric passage and it is currently going to the point of maximum separation between the subclusters.

astro-ph.CO↗

arXiv2017

The fate of the gaseous disks of galaxies that fall into clusters

Galaxy clusters are known to induce gas loss in infalling galaxies due to the ram pressure exerted by the intracluster medium over their gas content. In this paper, we investigate this process through a set of simulations of Milky Way like galaxies falling inside idealised clusters of 10$^{14}$ M$_\odot$ and 10$^{15}$ M$_\odot$, containing a cool-core or not, using the adaptive mesh refinement code RAMSES. We use these simulations to constrain how much of the initial mass contained in the gaseous disk of the galaxy will be converted into stars and how much of it will be lost, after a single crossing of the entire cluster. We find that, if the galaxy reaches the central region of a cool-core cluster, it is expected to lose all its gas, independently of its entry conditions and of the cluster's mass. On the other hand, it is expected to never lose all its gas after crossing a cluster without a cool-core just once. Before reaching the centre of the cluster, the SFR of the galaxy is always enhanced, by a factor of 1.5 to 3. If the galaxy crosses the cluster without being completely stripped, its final amount of gas is on average two times smaller after crossing the 10$^{15}$ M$_\odot$ cluster, relative to the 10$^{14}$ M$_\odot$ cluster. This is reflected in the final SFR of the galaxy, which is also two times smaller in the former, ranging from 0.5 $-$ 1 M$_\odot$ yr$^{-1}$, compared to 1 $-$ 2 M$_\odot$ yr$^{-1}$ for the latter.

astro-ph.GA↗

arXiv2015

Structure and dynamics of the supercluster of galaxies SC0028-0005

According to the standard cosmological scenario, superclusters are objects that have just passed the turn around point and are collapsing. The dynamics of very few superclusters have been analysed up to now. In this paper we study the supercluster SC0028-0005, at redshift 0.22, identify the most prominent groups and/or clusters that make up the supercluster, and investigate the dynamic state of this structure. For the membership identification, we have used photometric and spectroscopic data from SDSS-DR10, finding 6 main structures in a flat spatial distribution. We have also used a deep multi-band observation with MegaCam/CFHT to estimate de mass distribution through the weak-lensing effect. For the dynamical analysis, we have determined the relative distances along the line of sight within the supercluster using the Fundamental Plane of early-type galaxies. Finally, we have computed the peculiar velocities of each of the main structures. The 3D distribution suggests that SC0028-005 is indeed a collapsing supercluster, supporting the formation scenario of these structures. Using the spherical collapse model, we estimate that the mass within $r = 10$~Mpc should lie between 4 and $16 \times 10^{15} M_\odot$. The farthest detected members of the supercluster suggest that within $\sim 60$~Mpc the density contrast is $δ\sim 3$ with respect to the critical density at $z=0.22$, implying a total mass of $\sim 4.6$--$16 \times 10^{17} M_\odot$, most of which in the form of low-mass galaxy groups or smaller substructures.

astro-ph.GA↗

arXiv2015

Simulating the shocks in the dissociative galaxy cluster Abell 1758N

Major mergers between massive clusters have a profound effect in the intracluster gas, which may be used as a probe of the dynamics of structure formation at the high end of the mass function. An example of such a merger is observed at the northern component of Abell 1758, comprised of two massive sub-clusters separated by approximately 750 kpc. One of the clusters exhibits an offset between the dark matter and the intracluster gas. We aim to determine whether it is possible to reproduce the specific morphological features of this cluster by means of a major merger. We perform dedicated SPH (smoothed particle hydrodynamics) N-body simulations in an attempt to simultaneously recover several observed features of Abell 1758, such as the X-ray morphology and the separation between the two peaks in the projected galaxy luminosity map. We propose a specific scenario for the off-axis collision of two massive clusters. This model adequately reproduces several observed features and suggests that Abell 1758 is seen approximately 0.4 Gyr after the first pericentric passage, and that the clusters are already approaching their maximum separation. This means that their relative velocity is as low as 380 km/s. At the same time, the simulated model entails shock waves of ~4500 km/s, which are currently undetected presumably due to the low-density medium. We explain the difference between these velocities and argue that the predicted shock fronts, while plausible, cannot be detected from currently available data.

astro-ph.CO↗

arXiv2014

Simulations of gas sloshing in galaxy cluster Abell 2052

The intracluster plasma of Abell 2052 exhibits in X-rays a spiral structure extending more than 250 kpc, which is comprised of cool gas. This feature is understood to be the result of gas sloshing caused by the off-axis collision with a smaller subcluster. We aim to recover the dynamical history of Abell 2052 and to reproduce the broad morphology of the spiral feature. To this end, we perform hydrodynamical $N$-body simulations of cluster collisions. We obtain two regimes that adequately reproduce the desired features. The first scenario is a close encounter and a recent event (0.8 Gyr since pericentric passage), while the second scenario has a larger impact parameter and is older (almost 2.6 Gyr since pericentric passage). In the second case, the simulation predicts that the perturbing subcluster should be located approximately 2 Mpc from the centre of the major cluster. At that position, we are able to identify an observed optical counterpart at the same redshift: a galaxy group with $M_{500} = (1.16 \pm 0.43) \times 10^{13} M_{\odot}$.

astro-ph.CO↗

arXiv2013

Simulations of the merging galaxy cluster Abell 3376

Observed galaxy clusters often exhibit X-ray morphologies suggestive of recent interaction with an infalling subcluster. Abell 3376 is a nearby (z=0.046) massive galaxy cluster whose bullet-shaped X-ray emission indicates that it may have undergone a recent collision. It displays a pair of Mpc-scale radio relics and its brightest cluster galaxy is located 970 h_70^-1 kpc away from the peak of X-ray emission, where the second brightest galaxy lies. We attempt to recover the dynamical history of Abell 3376. We perform a set of N-body adiabatic hydrodynamical simulations using the SPH code Gadget-2. These simulations of binary cluster collisions are aimed at exploring the parameter space of possible initial configurations. By attempting to match X-ray morphology, temperature, virial mass and X-ray luminosity, we set approximate constraints on some merger parameters. Our best models suggest a collision of clusters with mass ratio in the range 1/6-1/8, and having a subcluster with central gas density four times higher than that of the major cluster. Models with small impact parameter (b<150 kpc), if any, are preferred. We estimate that Abell 3376 is observed approximately 0.5 Gyr after core passage, and that the collision axis is inclined by i~40 degrees with respect to the plane of the sky. The infalling subcluster drives a supersonic shock wave that propagates at almost 2600 km/s, implying a Mach number as high as M~4; but we show how it would have been underestimated as M~3 due to projection effects.

astro-ph.CO↗

arXiv2012

Simulations of galaxy cluster mergers: the dynamics of Abell 3376

In large scale structure formation, massive systems assemble through the hierarchical merging of less massive ones. Galaxy clusters, being the most massive and thus the most recent collapsed structures, still grow by accreting smaller clusters and groups. In order to investigate the dynamical evolution of the intracluster medium, we perform a set of adiabatic hydrodynamical simulations of binary cluster mergers.

astro-ph.CO↗

arXiv2012

A New Method to Quantify X-ray Substructures in Clusters of Galaxies

We present a new method to quantify substructures in clusters of galaxies, based on the analysis of the intensity of structures. This analysis is done in a residual image that is the result of the subtraction of a surface brightness model, obtained by fitting a two-dimensional analytical model (beta-model or Sérsic profile) with elliptical symmetry, from the X-ray image. Our method is applied to 34 clusters observed by the Chandra Space Telescope that are in the redshift range 0.02<z<0.2 and have a signal-to-noise ratio greater than 100. We present the calibration of the method and the relations between the substructure level with physical quantities, such as the mass, X-ray luminosity, temperature, and cluster redshift. We use our method to separate the clusters in two sub-samples of high and low substructure levels. We conclude, using Monte Carlo simulations, that the method recuperates very well the true amount of substructure for small angular core radii clusters (with respect to the whole image size) and good signal-to-noise observations. We find no evidence of correlation between the substructure level and physical properties of the clusters such as mass, gas temperature, X-ray luminosity and redshift. The scaling relations for the two sub-samples (high and low substructure level clusters) are different (they present an off-set, i.e., given a fixed mass or temperature, low substructure clusters tend to be more X-ray luminous), which is an important result for cosmological tests using the mass-luminosity relation to obtain the cluster mass function, since they rely on the assumption that clusters do not present different scaling relations according to their dynamical state.

astro-ph.CO↗