arXiv subjects

Susana E. Pedrosa

Publications and source records attributed to Susana E. Pedrosa.

At least 19 recordsLinked to original sources

arXiv2026

Mass density structuring around galaxy formation sites: impact on galaxy basic properties

We study the local evolution of the Universe around galaxy formation sites in the EAGLE50 large-volume reference simulation. Using the reduced inertia tensor (r-TOI), we followed the anisotropic evolution of initially spherical Lagrangian volumes (LVs) centred at galaxy formation sites, both in dark matter (DM) and in cold baryons (CB), from very high redshift $z=15$ onward. We describe LV deformation in terms of the r-TOI eigen-directions, principal axes, their derived shape parameters, and the timescales for the freezing-out of these principal directions and axes. Of particular interest are the age of the Universe, $t_{\rm U}$, when the local Cosmic Web (CW) spine emerges, and that when anisotropic DM mass arrangements (i.e., migrant mass flows) cease. We find that the shapes LVs acquire along their evolution affect the halo and stellar mass of their central galaxy: prolate-shaped LVs show a tendency to host low-mass galaxies at $z=0$, while massive galaxies tend to form within triaxial or oblate LVs. Also, the local CW spine tends to set in earlier on in LVs that are to host massive galaxies than in those harbouring less massive galaxies. In addition, anisotropic DM-mass rearrangements stop late on average, at $t_{\rm U}\sim 10.5\,$Gyr, and even slightly later for CB. Interestingly, $z=0$ LVs with either flattened configurations in CB or those that are highly prolate in DM, are more likely to host rotation-dominated galaxies. This effect increases from $z=1$ to $z=0$. Finally, the CB spine of LVs that are more likely to host rotation-dominated galaxies emerges at later times.

astro-ph.GA↗

arXiv2025

A statistical look on kinematic planes of satellite galaxies I: frequency and properties in TNG50 MW/M31-like galaxies

We use the TNG50 simulation to explore the possible existence of satellite galaxy sets, with fixed-in-time identities, forming kinematically-persistent planes (KPPs) along cosmic time around 190 MW/M31-like galaxies. This is the first study to assess their frequency within the $Λ$CDM framework. We identify KPPs around 46 of these host galaxies, with at least 25\% of their satellites in such configurations. Thereby, KPPs appear more frequent than previously reported, appearing in $\sim24\%$ of MW/M31-like systems, and in $\sim40\%$ of those populated with $N_{\rm sat}\geq9$. We find a dependency of the former frequency on the minimum satellite stellar mass cut, suggesting that it would increase with higher mass resolution. KPP satellite members form a distinct set compared to satellites outside KPPs, located at further distances from the center of their host and maintaining higher specific angular momentum since high redshift. KPP satellites form thin and oblate planes in positional space during long periods of cosmic time. We statistically confirm that KPPs form a kind of backbone of observationally-detected positional planes, and that, in velocity space, KPPs behave as kinematic morphological disks. We show that KPP formation, defined as the time when satellite orbital poles align around a specific, fixed direction (occurring at Universe age $\sim4$ Gyr), predates the end of halo's fast-phase of mass assembly, indicating that halo processes do not drive this clustering. Finally, our results are broadly consistent with the MW's kinematic plane at $z=0$ concerning its morphological properties and degree of satellite orbital poles clustering, mitigating the tension between the existence of these structures and the $Λ$CDM paradigm.

astro-ph.GA↗

arXiv2024

The origin of kinematically-persistent planes of satellite galaxies as driven by the early evolution of the local Cosmic Web in $Λ$CDM

Kinematically-persistent planes of satellites (KPPs) are fixed sets of satellites co-orbiting around their host galaxy, whose orbital poles are conserved and clustered across long cosmic time intervals. They play the role of 'skeletons', ensuring the long-term durability of positional planes. We explore the physical processes behind their formation in terms of the dynamics of the local Cosmic Web (CW), characterized via the so-called Lagrangian Volumes (LVs) built up around two zoom-in, cosmological hydro-simulations of MW-mass disk galaxy + satellites systems, where three KPPs have been identified. By analyzing the LVs deformations in terms of the reduced Tensor of Inertia (TOI), we find an outstanding alignment between the LV principal directions and KPP satellites' orbital poles. The most compressive local mass flows (along the $\hat{e}_3$ eigenvector) are strong at early times, feeding the so-called $\hat{e}_3$-structure, while the smallest TOI axis rapidly decreases. The $\hat{e}_3$-structure collapse marks the end of this regime and is the timescale for the establishment of satellite orbital pole clustering when the Universe is $\lesssim$ 4 Gyr old. KPP proto-satellites aligned with $\hat{e}_3$ are those whose orbital poles are either aligned from early times, or have been successfully bent at $\hat{e}_3$-structure collapse. KPP satellites associated to $\hat{e}_1$ tend to have early trajectories already parallel to $\hat{e}_3$. We show that KPPs can arise as a result of the $Λ$CDM-predicted large-scale dynamics acting on particular sets of proto-satellites, the same dynamics that shape the local CW environment.

astro-ph.GA↗

arXiv2022

Planes of satellites around simulated disk galaxies II: Time-persistent planes of kinematically-coherent satellites in $Λ$CDM

We use two zoom-in $Λ$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.

astro-ph.GA↗

arXiv2021

The evolution of the oxygen abundance gradients in star-forming galaxies in the EAGLE simulations

We analyse the evolution of the oxygen abundance gradient of star-forming galaxies with stellar mass Mstar > 10^9 Mo in the EAGK simulation over the redshift range z=[0, 2.5]. We find that the median metallicity gradient of the simulated galaxies is close to zero at all z, whereas the scatter around the median increases with z. The metallicity gradients of individual galaxies can evolve from strong to weak and vice-versa, since mostly low-metallicity gas accretes onto the galaxy, resulting in enhanced star formation and ejection of metal enriched gas by energy feedback. Such episodes of enhanced accretion, mainly dominated by major mergers, are more common at higher z, and hence contribute to increasing the diversity of gradients. For galaxies with negative metallicity gradients, we find a redshift evolution of ~ -0.03 dex/kpc/δz$. A positive mass dependence is found at z< 0.5, which becomes slightly stronger for higher redshifts and, mainly, for Mstar < 10^9.5 Mo. Only galaxies with negative metallicity gradients define a correlation with galaxy size, consistent with an inside-out formation scenario. Our findings suggest that major mergers and/or significant gas accretion can drive strong negative or positive metallicity gradients. The first ones are preferentially associated with disc-dominated galaxies, and the second ones with dispersion-dominated systems. The comparison with forthcoming observations at high redshift will allow a better understanding of the potential role of metallicity gradients as a chemical probe of galaxy formation.

astro-ph.GA↗

arXiv2020

Planes of satellites around simulated disc galaxies: I.- Finding high-quality planar configurations from positional information and their comparison to MW/M31 data

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.

astro-ph.GA↗

arXiv2019

Non-parametric Morphologies of Galaxies in the EAGLE Simulation

We study the optical morphology of galaxies in a large-scale hydrodynamic cosmological simulation, the EAGLE simulation. Galaxy morphologies were characterized using non-parametric statistics (Gini, $M_{20}$, Concentration and Asymmetry) derived from mock images computed using a 3D radiative transfer technique and post-processed to approximate observational surveys. The resulting morphologies were contrasted to observational results from a sample of $\log_{10}(M_{*}/M_\odot) > 10$ galaxies at $z \sim 0.05$ in the GAMA survey. We find that the morphologies of EAGLE galaxies reproduce observations, except for asymmetry values which are larger in the simulated galaxies. Additionally, we study the effect of spatial resolution in the computation of non-parametric morphologies, finding that Gini and Asymmetry values are systematically reduced with decreasing spatial resolution. Gini values for lower mass galaxies are especially affected. Comparing against other large scale simulations, the non-parametric statistics of EAGLE galaxies largely agree with those found in IllustrisTNG. Additionally, EAGLE galaxies mostly reproduce observed trends between morphology and star formation rate and galaxy size. Finally, We also find a significant correlation between optical and kinematic estimators of morphologies, although galaxy classification based on an optical or a kinematic criteria results in different galaxy subsets. The correlation between optical and kinematic morphologies is stronger in central galaxies than in satellites, indicating differences in morphological evolution.

astro-ph.GA↗

arXiv2019

Dark Matter Response to Galaxy Assembly History

Aims: It is well known that the presence of baryons affects the dark matter host haloes. Exploring the galaxy assembly history together with the dark matter haloes properties through time can provide a way to measure these effects. Methods: We study the properties of four Milky Way mass dark matter haloes from the Aquarius project during their assembly history, between $z = 0 - 4$. In this work, we use the SPH run from Scannapieco et al. (2009) and the dark matter only counterpart as case studies. To asses the robustness of our findings, we compare them with one of the haloes run using a moving-mesh technique and different sub-grid scheme. Results: Our results show that the cosmic evolution of the dark matter halo profiles depends on the assembly history of the baryons. We find that the dark matter profiles do not significantly change with time, hence they become stable, when the fraction of baryons accumulated in the central regions reaches 80 percent of its present mass within the virial radius. Furthermore, the mass accretion history shows that the haloes that assembled earlier are those that contain a larger amount of baryonic mass aforetime, which in turn allows the dark matter halo profiles to reach a stable configuration earlier. For the SPH haloes, we find that the specific angular momentum of the dark matter particles within the five percent of the virial radius at z = 0, remains approximately constant from the time at which 60 percent of the stellar mass is gathered. We explore different theoretical and empirical models for the contraction of the haloes through redshift. A model to better describe the contraction of the haloes through redshift evolution must depend on the stellar mass content in the inner regions.

astro-ph.CO↗

arXiv2018

Non-parametric Morphologies of Mergers in the Illustris Simulation

We study non-parametric morphologies of mergers events in a cosmological context, using the Illustris project. We produce mock g-band images comparable to observational surveys from the publicly available Illustris simulation idealized mock images at $z=0$. We then measure non parametric indicators: asymmetry, Gini, $M_{20}$, clumpiness and concentration for a set of galaxies with $M_* >10^{10}$ M$_\odot$. We correlate these automatic statistics with the recent merger history of galaxies and with the presence of close companions. Our main contribution is to assess in a cosmological framework, the empirically derived non-parametric demarcation line and average time-scales used to determine the merger rate observationally. We found that 98 per cent of galaxies above the demarcation line have a close companion or have experienced a recent merger event. On average, merger signatures obtained from the $G-M_{20}$ criteria anticorrelate clearly with the elapsing time to the last merger event. We also find that the asymmetry correlates with galaxy pair separation and relative velocity, exhibiting the larger enhancements for those systems with pair separations $d < 50$ h$^{-1}$ kpc and relative velocities $V < 350$ km s$^{-1}$. We find that the $G-M_{20}$ is most sensitive to recent mergers ($\sim0.14$ Gyr) and to ongoing mergers with stellar mass ratios greater than 0.1. For this indicator, we compute a merger average observability time-scale of $\sim0.2$ Gyr, in agreement with previous results and demonstrate that the morphologically derived merger rate recovers the intrinsic total merger rate of the simulation and the merger rate as a function of stellar mass.

astro-ph.GA↗

arXiv2017

Mild evolution of the stellar metallicity gradients of disc galaxies

The metallicity gradients of the stellar populations in disc galaxies and their evolution store relevant information on the disc formation history and on those processes which could mix stars a posteriori, such as migration, bars and/or galaxy-galaxy interactions. We aim to investigate the evolution of the metallicity gradients of the whole stellar populations in disc components of simulated galaxies in a cosmological context. We analyse simulated disc galaxies selected from a cosmological hydrodynamical simulation that includes chemical evolution and a physically motivated Supernova feedback capable of driving mass-loaded galactic winds. We detect a mild evolution with redshift in the metallicity slopes of $-0.02 \pm 0.01$ dex~kpc$^{-1}$ from $z\sim 1$. If the metallicity profiles are normalised by the effective radius of the stellar disc, the slopes show no clear evolution for $z < 1$, with a median value of approximately $-0.23$ dex ~$r_{\rm reff}^{-1}$. As a function of stellar mass, we find that metallicity gradients steepen for stellar masses smaller than $\sim 10^{10.3} {\rm M_{\odot}}$ while the trend reverses for higher stellar masses, in the redshift range $z=[0,1]$. Galaxies with small stellar masses have discs with larger $r_{\rm reff}$ and flatter metallicity gradients than expected. We detect migration albeit weaker than in previous works. Our stellar discs show a mild evolution of the stellar metallicity slopes up to $z\sim 1,$ which is well-matched by the evolution calculated archeologically from the abundance distributions of mono-age stellar populations at $z\sim 0$. Overall, Supernova feedback could explain the trends but an impact of migration can not be totally discarded. Galaxy-galaxy interactions or small satellite accretions can also contribute to modify the metallicity profiles in the outer parts. [abridged]

astro-ph.GA↗

arXiv2017

Small-scale galaxy clustering in the EAGLE simulation

We study present-day galaxy clustering in the EAGLE cosmological hydrodynamical simulation. EAGLE's galaxy formation parameters were calibrated to reproduce the redshift $z=0.1$ galaxy stellar mass function, and the simulation also reproduces galaxy colours well. The simulation volume is too small to correctly sample large-scale fluctuations and we therefore concentrate on scales smaller than a few mega parsecs. We find very good agreement with observed clustering measurements from the Galaxy And Mass Assembly (GAMA) survey, when galaxies are binned by stellar mass, color, or luminosity. However, low-mass red-galaxies are clustered too strongly, which is at least partly due to limited numerical resolution. Apart from this limitation, we conclude that EAGLE galaxies inhabit similar dark matter haloes as observed GAMA galaxies, and that the radial distribution of satellite galaxies as function of stellar mass and colour is similar to that observed as well.

astro-ph.GA↗

arXiv2016

The stellar metallicity gradients in galaxy discs in a cosmological scenario

The stellar metallicity gradients of disc galaxies provide information on the disc assembly, star formation processes and chemical evolution. They also might store information on dynamical processes which could affect the distribution of chemical elements in the gas-phase and the stellar components. We studied the stellar metallicity gradients of stellar discs in a cosmological simulation. We explored the dependence of the stellar metallicity gradients on stellar age and the size and mass of the stellar discs. We used galaxies selected from a cosmological hydrodynamical simulation performed including a physically-motivated Supernova feedback and chemical evolution. The metallicity profiles were estimated for stars with different ages. We confront our numerical findings with results from the CALIFA Survey. The simulated stellar discs are found to have metallicity profiles with slopes in global agreement with observations. Low stellar-mass galaxies tend to have a larger variety of metallicity slopes. When normalized by the half-mass radius, the stellar metallicity gradients do not show any dependence and the dispersion increases significantly, regardless of galaxy mass. Galaxies with stellar masses around $10^{10}$M$_{\odot}$ show steeper negative metallicity gradients. The stellar metallicity gradients correlate with the half-mass radius. However, the correlation signal is not present when they are normalized by the half-mass radius. Stellar discs with positive age gradients are detected to have negative and positive metallicity gradients, depending on the relative importance of the recent star formation activity in the central regions. The large dispersions in the metallicity gradients as a function of stellar mass could be ascribed to the effects of dynamical processes such as mergers/interactions and/or migration as well as those regulating the conversion of gas into stars. [abridged]

astro-ph.GA↗

arXiv2015

The gas metallicity gradient and the star formation activity of disc galaxies

We study oxygen abundance profiles of the gaseous disc components in simulated galaxies in a hierarchical universe. We analyse the disc metallicity gradients in relation to the stellar masses and star formation rates of the simulated galaxies. We find a trend for galaxies with low stellar masses to have steeper metallicity gradients than galaxies with high stellar masses at z ~0. We also detect that the gas-phase metallicity slopes and the specific star formation rate (sSFR) of our simulated disc galaxies are consistent with recently reported observations at z ~0. Simulated galaxies with high stellar masses reproduce the observed relationship at all analysed redshifts and have an increasing contribution of discs with positive metallicity slopes with increasing redshift. Simulated galaxies with low stellar masses a have larger fraction of negative metallicity gradients with increasing redshift. Simulated galaxies with positive or very negative metallicity slopes exhibit disturbed morphologies and/or have a close neighbour. We analyse the evolution of the slope of the oxygen profile and sSFR for a gas-rich galaxy-galaxy encounter, finding that this kind of events could generate either positive and negative gas-phase oxygen profiles depending on their state of evolution. Our results support claims that the determination of reliable metallicity gradients as a function of redshift is a key piece of information to understand galaxy formation and set constrains on the subgrid physics.

astro-ph.GA↗

arXiv2013

Evolution of the gas kinematics of galaxies in cosmological simulations

We studied the evolution of the gas kinematics of galaxies by performing hydrodynamical simulations in a cosmological scenario. We paid special attention to the origin of the scatter of the Tully-Fisher relation and the features which could be associated with mergers and interactions. We extended the study by De Rossi et al. (2010) and analysed their whole simulated sample which includes both, gas disc-dominated and spheroid-dominated systems. We found that mergers and interactions can affect the rotation curves directly or indirectly inducing a scatter in the Tully-Fisher Relation larger than the simulated evolution since z=3. In agreement with previous works, kinematical indicators which combine the rotation velocity and dispersion velocity in their definitions lead to a tighter relation. In addition, when we estimated the rotation velocity at the maximum of the rotation curve, we obtained the best proxy for the potential well regardless of morphology.

astro-ph.CO↗

arXiv2012

Fingerprints of the hierarchical building up of the structure on the gas kinematics of galaxies

Recent observational and theoretical works have suggested that the Tully-Fisher Relation might be generalised to include dispersion-dominated systems by combining the rotation and dispersion velocity in the definition of the kinematical indicator. Mergers and interactions have been pointed out as responsible of driving turbulent and disordered gas kinematics, which could generate Tully-Fisher Relation outliers. We intend to investigate the gas kinematics of galaxies by using a simulated sample which includes both, gas disc-dominated and spheroid-dominated systems. Cosmological hydrodynamical simulations which include a multiphase model and physically-motivated Supernova feedback were performed in order to follow the evolution of galaxies as they are assembled. Both the baryonic and stellar Tully-Fisher relations for gas disc-dominated systems are tight while, as more dispersion-dominated systems are included, the scatter increases. We found a clear correlation between $σ/ V_{\rm rot}$ and morphology, with dispersion-dominated systems exhibiting the larger values ($> 0.7$). Mergers and interactions can affect the rotation curves directly or indirectly inducing a scatter in the Tully-Fisher Relation larger than the simulated evolution since $z \sim 3$. Kinematical indicators which combine rotation velocity and dispersion velocity can reduce the scatter in the baryonic and the stellar mass-velocity relations. Our findings also show that the lowest scatter in both relations is obtained if the velocity indicators are measured at the maximum of the rotation curve. Moreover, the rotation velocity estimated at the maximum of the gas rotation curve is found to be the best proxy for the potential well regardless of morphology.

astro-ph.CO↗

arXiv2011

The role of supernova feedback on the origin of the stellar and baryonic Tully-Fisher relations

In this work, we studied the stellar and baryonic Tully-Fisher relations by using hydrodynamical simulations in a cosmological framework. We found that supernova feedback plays an important role on shaping the stellar Tully-Fisher relation causing a steepening of its slope at the low-mass end, consistently with observations. The bend of the relation occurs at a characteristic velocity of approximately 100 km/s, in concordance with previous observational and theoretical findings. With respect to the baryonic Tully-Fisher relation, the model predicts a linear trend at z~0 with a weaker tendency for a bend at higher redshifts. In our simulations, this behaviour is a consequence of the more efficient action of supernova feedback at regulating the star formation process in smaller galaxies.

astro-ph.CO↗

arXiv2011

Supernova Feedback and the Bend of the Tully-Fisher Relation

We have studied the origin of the Tully-Fisher relation by analysing hydrodynamical simulations in a Lambda-CDM universe. We found that smaller galaxies exhibit lower stellar masses than those predicted by the linear fit to high mass galaxies (fast rotators), consistently with observations. In this model, these trends are generated by the more efficient action of Supernova feedback in the regulation of the star formation in smaller galaxies. Without introducing scale-dependent parameters, the model predicts that the Tully-Fisher relation bends at a characteristic velocity of around 100 km/s, in agreement with previous observational and theoretical findings.

astro-ph.CO↗

arXiv2010

Impact of Supernova feedback on the Tully-Fisher relation

Recent observational results found a bend in the Tully-Fisher Relation in such a way that low mass systems lay below the linear relation described by more massive galaxies. We intend to investigate the origin of the observed features in the stellar and baryonic Tully-Fisher relations and analyse the role played by galactic outflows on their determination. Cosmological hydrodynamical simulations which include Supernova feedback were performed in order to follow the dynamical evolution of galaxies. We found that Supernova feedback is a fundamental process in order to reproduce the observed trends in the stellar Tully-Fisher relation. Simulated slow rotating systems tend to have lower stellar masses than those predicted by the linear fit to the massive end of the relation, consistently with observations. This feature is not present if Supernova feedback is turned off. In the case of the baryonic Tully-Fisher relation, we also detect a weaker tendency for smaller systems to lie below the linear relation described by larger ones. This behaviour arises as a result of the more efficient action of Supernovae in the regulation of the star formation process and in the triggering of powerful galactic outflows in shallower potential wells which may heat up and/or expel part of the gas reservoir.

astro-ph.CO↗