arXiv subjects

Jenny Gonzalez-Jara

Publications and source records attributed to Jenny Gonzalez-Jara.

10 recordsLinked to original sources

arXiv2026

The properties of central stellar knots embedded in galactic bulges of CIELO simulations

Deeply bound stellar substructures of about 1 kpc at the center of bulges are found in a subset of galaxies from the cosmological chemo-hydrodynamical zoom-in CIELO simulation suite. They were identified as stellar overdensities at the lowest binding energies in each galaxy's circularity-energy $(ε, E)$ plane. We refer to these overdensities as stellar knots. We aim to characterize their properties in the context of bulge assembly using CIELO simulated galaxies spanning a wide range of stellar masses ($10^{8.0}$-$10^{10.7}\,\mathrm{M}_{\odot}$), with diverse formation histories. We inspect 54 galactic bulges. Within them, we isolate stellar knot candidates in $(ε, E)$ space, and identify 28 robust knots satisfying successive selection criteria: kinematic, concentration, and morphology. We characterize their chemical enrichment, formation timescales, formation sites, progenitor gas origin, and spatial distributions. Across all galaxy masses, knots are systematically alpha-element enhanced, having assembled the bulk of their stellar mass at earlier epochs and on shorter timescales than other bulge populations, with a median of $\sim$2$\,$Gyr versus $\sim$5$\,$Gyr. Regarding their origin, knots are predominantly in-situ ($5\%$ accreted mass fraction, roughly half that of the rest of the bulge), with negligible disk-born stars contribution and the largest gas fractions originating from a primordial central spheroid ($21\%$ versus 16--17$\%$ for the surrounding populations), consistent with being the primary gas fuel for the alpha-element enhancement. In terms of structure, knots exhibit a variety of morphologies, with spheroidal shapes predominating. Dynamical selection in $(ε, E)$ space of CIELO galaxies demonstrates its effectiveness in recovering coeval stellar populations, pointing to stellar knots as plausible fossil signatures of early in-situ bulge assembly.

astro-ph.GA↗

arXiv2026

Angular momentum evolution in the CIELO simulations. I. Temporal evolution of gas-stellar misalignments and baryonic merger timing

Gas-stellar kinematic misalignments trace how galaxies assemble and reorient their angular momentum. Although well documented locally, their continuous evolution remains largely unexplored. We aim to characterise the pathways linking aligned, misaligned, and counter-rotating phases, assessing how gas accretion channels and mergers drive reorientation. We analysed 44 central galaxies from the CIELO simulations from z=3.5 to z=0. We defined kinematic episodes using the intrinsic angle, psi, between the star-forming (SF) gas and stellar angular momentum vectors, interpreting these histories by tracking accreted gas origins and evaluating paired statistical contrasts. Nearly 80% of the simulated galaxies are aligned at z=0, yet 86% experience at least one non-aligned episode. Although 19% of non-aligned episodes last >2 Gyr, their durations do not differ significantly from aligned episodes. Abrupt changes in psi coincide with intervals where accreted gas dominates the pre-existing SF reservoir and is highly tilted relative to pre-existing stars. During transitions, the median mass ratio of accreted to pre-existing SF gas rises from 0.57 to 2.14, and the median angular offset increases from 21.2 to 64.6 deg. While relevant mergers cluster near these boundaries, they can drive either alignment or misalignment regardless of mass ratios or orbits. Instead, mergers triggering abrupt transitions typically encounter hosts that are already partially decoupled. In the simulated sample, gas-stellar misalignment is fundamentally driven by reservoir competition. Mergers act as conditional triggers, but a galaxy's ultimate kinematic fate depends strictly on how newly accreted gas couples to, replaces, or mixes with the pre-existing material as it joins the central SF reservoir.

astro-ph.GA↗

arXiv2026

The heartbeat of stellar halos: Insights from the stellar halo mass-metallicity relation

This work investigates the presence and evolution of the MZhR from redshift z=3.5 to z=0, and identifies when galaxies settle on the present-day MZhR. We used central galaxies with log10(Mgal/Msun)=[9,11] from CIELO simulations. We identified stellar halos, from z=3.5 to z=0, using the AM-E method, focusing on the region between the 1.5 optical radius and the virial radius. We presented halo cardiograms, a novel approach to studying the assembly history of stellar halos. Using them, we defined a stability time (tst) as the first time that the median halo metallicity does not change more than \pm 0.1 dex with respect to its value at z=0. CIELO stellar halos reproduce the present-day observed MZhR. At z=3.5, stellar halos already define an MZhR whose slope is similar to the slope at z=0. For a fixed stellar halo mass, the metallicity increases ~0.21 dex from z=3.5 to z=0, reflecting the progressive chemical enrichment provided by the accretion of satellites with diverse masses and different levels of enrichment. When the first stellar halo main contributor (SHMC1) provides a mass fraction at least 20% higher than the remaining contributors, the stellar halo metallicity is set once SHMC1 is fully disrupted (tmerger). This yields a clear correlation between tst and tmerger, with a scatter of 2.2 Gyr driven by the relative importance of the second and third main contributing satellites. We provide two observational tracers for tst: t90 and a stability time from the age-metallicity relation. Our results suggest that estimating tst could serve as a proxy for dating the moment at which the stellar halo reaches the present-day MZhR, as well as for dating the last major merger that builds them. Combined with an estimation of the merger time of the main contributing satellite, it can provide insights into the relative importance of the second and third contributing satellites. (abridged)

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arXiv2026

Metal-loaded outflows in sub-Milky Way galaxies in the CIELO simulations

Supernova (SN) feedback-driven galactic outflows are a key physical process that contributes to the baryon cycle by regulating the star formation activity, reducing the amount of metals in low-mass galaxies and enriching the circumgalactic (CGM) and intergalactic media (IGM). We aim to understand the chemical loop of sub-Milky Way (MW) galaxies and their nearby regions. We studied 15 simulated central sub-MW galaxies (M* <= 10^10 Msun) and intermediate-mass galaxies (M* \sim 10^10 Msun) from the CIELO-P7 high-resolution simulations. We followed the evolution of the progenitor galaxies, their properties and the characteristics of the outflows within the redshift range z = [0, 7]. We used two dynamically-motivated outflow definitions, unbound outflows and expelled mass rates, to quantify the impact of SN feedback. At z \sim 0, sub-MW galaxies have a larger fraction of their current oxygen mass in the gas phase but have expelled a greater portion beyond the virial radius, compared to their higher-mass counterparts. Galaxies with M* <\sim 10^9 Msun have 10-40 per cent of their total oxygen mass within R200 in the CGM, and an equivalent to 10-60 per cent expelled into the IGM. In contrast, more massive galaxies have most of the oxygen mass locked by the stellar populations. The CGM of low-mass galaxies predominantly contains oxygen low-temperature gas, acting as a metal reservoir. We find that the outflows are more oxygen-rich for sub-MW galaxies, Zout/ZISM \sim 1.5, than for higher-mass galaxies, Zout/ZISM <= 0.5, particularly for z < 2. Mass-loading factors of eta_out \sim 0 - 6 are detected in agreement with observations (abridged).

astro-ph.GA↗

arXiv2025

Aletheia: Emulating the non-linear matter power spectrum in the context of evolution mapping

We present Aletheia, a new emulator of the non-linear matter power spectrum, $P(k)$, built upon the evolution mapping framework. This framework addresses the limitations of traditional emulation by focusing on $h$-independent cosmological parameters, which can be separated into those defining the linear power spectrum shape ($\mathbfΘ_{\mathrm{s}}$) and those affecting only its amplitude evolution ($\mathbfΘ_{\mathrm{e}}$). The combined impact of evolution parameters and redshift is compressed into a single amplitude parameter, $σ_{12}$. Aletheia uses a two-stage Gaussian Process emulation: a primary emulator predicts the non-linear boost factor as a function of ($\mathbfΘ_{\mathrm{s}}$) and $σ_{12}$ for fixed evolution parameters, while a second one applies a small linear correction based on the integrated growth history. The emulator is trained on shape parameters spanning $\pm$5$σ$ of Planck constraints and a wide clustering range $0.2 < σ_{12} < 1.0$, providing predictions for $0.006\,{\rm Mpc}^{-1} < k < 2\,{\rm Mpc}^{-1}$. We validate Aletheia against N-body simulations, demonstrating sub-percent accuracy. When tested on a suite of dynamic dark energy models, the full emulator's predictions show a variance of approximately 0.2%, a factor of five smaller than that of the state-of-the-art EuclidEmulator2 (around 1% variance). Furthermore, Aletheia maintains sub-percent accuracy for the best-fit dynamic dark energy cosmology from recent DESI data, a model whose parameters lie outside the training ranges of most conventional emulators. This demonstrates the power of the evolution mapping approach, providing a robust and extensible tool for precision cosmology.

astro-ph.CO↗

arXiv2025

The mass-metallicity relation of bulges

Context. Bulges, located at the central regions of galaxies, are complex structures, expected to be shaped by the physical processes involved in the assembly history of their host galaxy, such as gravitational collapse, mergers, interactions, and bars. As a consequence a variety of bulges with distinct morphology and chemistry could be produced. Aim. We aim at exploring the existence of a stellar mass-metallicity relation of bulges, MZ*R, and analyze the possible imprint of characteristics features by accretion and migration of stars, which could store information on their assembly histories. Methods. We use 44 central galaxies from the CIELO cosmological simulations. Their stellar masses are within the range of [10^7.6, 10^10.6] Msun. We decomposed the galaxy into bulge and disk using the circularity and binding energies. We track the stellar populations in bulges back in time to their birth location, classifying them as bulge-born in-situ, and disk-born stars and accreted. Results. We find that most of the stars in our bulges are formed in-situ, but 33% of our bulges show a non-negligible contribution of stellar accretion from satellites, which could add to about 35% of the population. The accreted material is generally contribute by two or three satellites at most. In some bulges, we also find up to a 32% of stars that migrated from the disk due to secular evolution, with a median of 10%. Regardless of the formation histories, we found a clear MZ*R for bulges, which is more enriched by about 0.4 dex than the corresponding relation of the disk components, and about 0.15 dex more enriched than the galaxy MZ*R. We find evidence that the dispersion in the bulge MZ*R is influenced by both stellar accretion from satellites and migration from the disk, such that, at a fixed bulge mass, bulges with higher fraction of accreted and migrated stars tend to be less metal-rich (abridged).

astro-ph.GA↗

arXiv2025

Insight into the physical processes that shape the metallicity profiles in galaxies

The distribution of chemical elements in the star-forming regions can store information on the chemical enrichment history of the galaxies. Negative metallicity gradients are expected in galaxies forming inside-out. However, observations show that the metallicity profiles can be broken. We aim to study the diversity of metallicity profiles that can arise in the current cosmological context and compare them with available observations. We also seek to identify the physical processes responsible for breaks in metallicity profiles by using two galaxies as case studies. We analyze central galaxies from the cosmological simulations of the CIELO project, within the stellar mass range [$10^{8.5}$, $10^{10.5}$] M$_\odot$ at $z=0$. A new algorithm, DB-A, was developed to fit multiple power laws to the metallicity profiles, enabling a flexible assessment of metallicity gradients in various galactic regions. The simulations include detailed modeling of gas, metal-dependent cooling, star formation, and supernova feedback. At $z=0$, we find diverse profile shapes, including inner and outer drops and rises, with some galaxies exhibiting double breaks. Gradient values align with observations. A temporal analysis of Local Group analogs shows inner and outer breaks occurring at all cosmic times, with outer breaks being more frequent. Metallicity gradients show high variability at high redshift, transitioning to mild evolution at lower redshift. Most inner breaks show central oxygen enhancement, linked to gas accretion and star formation. Inner drops result from disrupted gas due to feedback-driven outflows. Outer breaks with high metallicities arise from re-accreted material, extended star formation, and CGM-driven gas mixing. Outer drops are common at high redshift, linked to metal-poor gas accretion from cold flows. We highlight the complex interplay of these processes which often act together.

astro-ph.GA↗

arXiv2025

The role of accreted and in situ populations in shaping the stellar halos of low-mass galaxies

The stellar halos of dwarf galaxies are becoming an object of interest in the extragalactic community due to their detection in some recent observations. Additionally, new cosmological simulations of very high resolution were performed, allowing their study. These stellar halos could help shed light on our understanding of the assembly of dwarf galaxies and their evolution, and allow us to test the hierarchical model for the formation of structures at small scales. We aim to characterise the stellar halos of simulated dwarf galaxies and analyse their evolution and accretion history. We use a sample of 17 simulated galaxies from the Auriga Project with a stellar mass range from 3.28x10^8 Msun to 2.08x10^10 Msun. We define the stellar halo as the stellar material located outside an ellipsoid with semi-major axes equal to 4 times the half light radius (Rh) of each galaxy. We find that the inner regions of the stellar halo (4 to 6 times the Rh) are dominated by in-situ material. For the less massive simulated dwarfs (M*<=4.54x10^8 Msun), this dominance extends to all radii. We find that this in-situ stellar halo is mostly formed in the inner regions of the galaxies and then ejected into the outskirts during interactions and merger events. In ~50% of the galaxies, the stripped gas from satellites contributed to the formation of this in-situ halo. The stellar halos of the galaxies more massive than M*>=1x10^9 Msun are dominated by the accreted component beyond 6 Rh. We find that the more massive dwarf galaxies accrete stellar material until later times (t90~4.44 Gyr ago, being t90 the formation time) than the less massive ones (t90~8.17 Gyr ago), impacting on the formation time of the accreted stellar halos. The galaxies have a range of 1 to 7 significant progenitors contributing to their accreted component but there is no correlation between this quantity and the galaxies' accreted mass.

astro-ph.GA↗

arXiv2025

The CIELO Project: The Chemo-dynamical properties of gaLaxies and the cosmic web

The CIELO project introduces a novel set of chemo-dynamical zoom-in simulations designed to simultaneously resolve galaxies and their nearby environments. The initial conditions include a diverse range of cosmic structures, such as local groups, filaments, voids, and walls, allowing for a detailed exploration of galaxies within the broader context of the cosmic web. This study presents the initial conditions and characterizes the global properties of CIELO galaxies and their environments. It focuses on galaxies with stellar masses ranging from log [8,11] solar masses and examines key scaling relations, including the mass-size relation, the Tully-Fisher relation, and the mass-metallicity relation for both stars and star-forming gas. The DisPerSe algorithm was used to determine the positions of CIELO galaxies within the cosmic web, with a specific focus on the Pehuen haloes. The selection of local group volumes was guided by criteria based on the relative positions and velocities of the two primary galaxies. The Pehuen regions were chosen to map walls, filaments, and voids. Synthetic images in the SDSS i, r, and g bands were generated using the SKIRT radiative transfer code. Additionally, a dynamical decomposition was performed to classify galaxy morphologies into bulge, disc, and stellar halo components (abridged).

astro-ph.GA↗

arXiv2024

Unveiling the formation channels of stellar halos through their chemical fingerprints

Stellar halos around galaxies contain key information about their formation and assembly history. Using simulations, we can trace the origins of different stellar populations in these halos, contributing to our understanding of galaxy evolution. We aim to investigate the assembly of stellar halos and their chemical abundances in 28 galaxies from CIELO project with logMgal[9 and 11]Msun. Stellar halos were identified using the AM E method, focusing on the outer regions between the 1.5 optical radius and the virial radius. We divided the stellar populations based on their formation channel: exsitu, endodebris, and insitu, and analyzed their chemical abundances, ages, and spatial distributions. Additionally, we explored correlations between halo mass, metallicity, and alpha element enrichment. CIELO simulations reveal that stellar halos are predominantly composed of accreted material (exsitu and endodebris stars), in agreement with previous works. The mass fraction of these populations is independent of stellar halo mass, though their metallicities scale linearly with it. Exsitu stars tend to dominate the outskirts and be more alpha rich and older, while endodebris stars are more prevalent at lower radii and tend to be less alpha rich and slightly younger. Massive stellar halos require a median of five additional satellites to build 90 percent of their mass, compared to lower mass halos, which typically need fewer (median of 2.5) and lower-mass satellites and are assembled earlier. The diversity of accreted satellite histories results in well defined stellar halo mass metallicity and [alpha/Fe] [Fe/H] relations, offering a detailed view of the chemical evolution and assembly history of stellar halos. We find that the [alpha/Fe] [Fe/H] is more sensitive to the characteristics and star formation history of the contributing satellites than the stellar halo mass metallicity relationship

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