The Milky Way’s inner region is dominated by a stellar bar and a boxy-peanut-shaped bulge. However, which stellar populations inhabit the inner Galaxy or how star formation proceeded there is still unknown. The difficulty in studying these stars stems from their location in dense regions that are strongly impacted by extinction and crowding effects. In this work we used star formation histories computed in the solar neighbourhood via Gaia colour-magnitude diagram fitting to shed light on the evolution of the central regions of our Galaxy. For that, we obtained precise age distributions for the non-negligible amount of super-metal-rich stars ([M/H] ∼ 0.5) in the solar neighbourhood (more than 5% of the total stars within 400 pc of the plane). Assuming that these stars were born in the inner Galaxy and migrated outwards, those distributions should be indicative of the true stellar age distribution in the inner Galaxy. Surprisingly, we find that these age distributions are not continuous but show clear signs of episodic star formation (∼13.5, 10.0, 7.0, 4.0, 2.0, and less than 1 Gyr ago). Interestingly, with the exception of the 4 Gyr event, the timings of the detected events coincide with the formation of the primitive Milky Way and with known merging events or satellite encounters ( Gaia -Enceladus-Sausage, Sagittarius dwarf galaxy, and the Magellanic Clouds), suggesting that these events could have triggered global star-forming episodes. These results are compatible with a scenario in which Gaia -Enceladus-Sausage is responsible for the formation of the bar 10 Gyr ago. However, we cannot associate any accretion counterpart with the event that occurred 4 Gyr ago, leaving open the possibility of a late formation of the bar, as previously proposed. The Auriga Superstars simulations also indicate that metal-rich stars in the solar neighbourhood-like regions formed at discrete times and migrated from the inner parts of barred galaxies, suggesting a possible link to bar dynamics and satellite accretion. This novel analysis allows us to indirectly witness the evolution of the inner Milky Way and constrain dynamical models of the Milky Way bar.

The mass in the Universe is distributed non-uniformly, leading to the large scale structure (LSS), characterised by clusters, filaments, walls, and voids. Galaxies in voids have been found to be bluer, of later type, less massive, and to have slower evolution than galaxies in denser large-scale environments. The effect of the void environment on many other evolutionary properties, such as the star formation rate (SFR), is still a topic of discussion. We tackled this problem from a new perspective by estimating the spatially resolved SFR derived from extinction-corrected H alpha luminosities of a sample of 220 void galaxies from the Calar Alto Void Integral-field Treasury surveY (CAVITY) project. These observations consist of optical integral field unit data cubes obtained with the PMAS/PPaK spectrograph at the 3.5 m telescope at the Calar Alto Observatory (Almer & iacute;a, Spain). We measured their continuum-subtracted emission lines to obtain the maps of the SFR, specific star formation rate (sSFR), and extinction (A(V)). From these values, we assessed the behaviours of the entire galaxies through their global properties, and the spatially resolved information with radial profiles up to two half-light radii. We then compared the results with a sample of galaxies in filaments and walls from the CALIFA survey analysed using the same methodology. We built a control sample matched in morphological type and total stellar mass by taking pairs of each CAVITY galaxy. We find no statistically significant differences in the SFR and sSFR (p <= 0.05), although void galaxies tend to have larger SFRs, especially for the early spirals. This effect is present for Sa galaxies at all galactocentric distances (Delta log sSFR [Gyr(-1)] = 0.25 dex at 1 half light radius, HLR), and it can also be seen in the outer parts (R > 1 HLR) of late-type spirals (Delta log sSFR [Gyr(-1)] = 0.26 dex at 2 HLR), evidencing a slower transition from star-forming to quiescent and less evolved spiral discs. Additionally, we find void late-type galaxies to have lower extinction (Delta = 0.16 +/- 0.06 mag). Using the extinction normalised by the stellar mass surface density as a proxy for the gas mass fraction, we find it to be larger for the void early spirals (by a 5%), especially in their outer regions (23% larger). This indicates the effect of the void environment on the transition stage from star forming to passive.

The Milky Way's inner region is dominated by a stellar bar and a boxy-peanut-shaped bulge. However, which stellar populations inhabit the inner Galaxy or how star formation proceeded there is still unknown. The difficulty in studying these stars stems from their location in dense regions that are strongly impacted by extinction and crowding effects. In this work we used star formation histories computed in the solar neighbourhood via Gaia colour-magnitude diagram fitting to shed light on the evolution of the central regions of our Galaxy. For that, we obtained precise age distributions for the non-negligible amount of super-metal-rich stars ([M/H] similar to 0.5) in the solar neighbourhood (more than 5% of the total stars within 400 pc of the plane). Assuming that these stars were born in the inner Galaxy and migrated outwards, those distributions should be indicative of the true stellar age distribution in the inner Galaxy. Surprisingly, we find that these age distributions are not continuous but show clear signs of episodic star formation (similar to 13.5, 10.0, 7.0, 4.0, 2.0, and less than 1 Gyr ago). Interestingly, with the exception of the 4 Gyr event, the timings of the detected events coincide with the formation of the primitive Milky Way and with known merging events or satellite encounters (Gaia-Enceladus-Sausage, Sagittarius dwarf galaxy, and the Magellanic Clouds), suggesting that these events could have triggered global star-forming episodes. These results are compatible with a scenario in which Gaia-Enceladus-Sausage is responsible for the formation of the bar 10 Gyr ago. However, we cannot associate any accretion counterpart with the event that occurred 4 Gyr ago, leaving open the possibility of a late formation of the bar, as previously proposed. The Auriga Superstars simulations also indicate that metal-rich stars in the solar neighbourhood-like regions formed at discrete times and migrated from the inner parts of barred galaxies, suggesting a possible link to bar dynamics and satellite accretion. This novel analysis allows us to indirectly witness the evolution of the inner Milky Way and constrain dynamical models of the Milky Way bar.

The mass in the Universe is distributed non-uniformly, leading to the large scale structure (LSS), characterised by clusters, filaments, walls, and voids. Galaxies in voids have been found to be bluer, of later type, less massive, and to have slower evolution than galaxies in denser large-scale environments. The effect of the void environment on many other evolutionary properties, such as the star formation rate (SFR), is still a topic of discussion. We tackled this problem from a new perspective by estimating the spatially resolved SFR derived from extinction-corrected Hα luminosities of a sample of 220 void galaxies from the Calar Alto Void Integral-field Treasury surveY (CAVITY) project. These observations consist of optical integral field unit data cubes obtained with the PMAS/PPaK spectrograph at the 3.5 m telescope at the Calar Alto Observatory (Almería, Spain). We measured their continuum-subtracted emission lines to obtain the maps of the SFR, specific star formation rate (sSFR), and extinction (AV). From these values, we assessed the behaviours of the entire galaxies through their global properties, and the spatially resolved information with radial profiles up to two half-light radii. We then compared the results with a sample of galaxies in filaments and walls from the CALIFA survey analysed using the same methodology. We built a control sample matched in morphological type and total stellar mass by taking pairs of each CAVITY galaxy. We find no statistically significant differences in the SFR and sSFR (p ≤ 0.05), although void galaxies tend to have larger SFRs, especially for the early spirals. This effect is present for Sa galaxies at all galactocentric distances (Δ log sSFR [Gyr−1] = 0.25 dex at 1 half light radius, HLR), and it can also be seen in the outer parts (R > 1 HLR) of late-type spirals (Δ log sSFR [Gyr−1] = 0.26 dex at 2 HLR), evidencing a slower transition from star-forming to quiescent and less evolved spiral discs. Additionally, we find void late-type galaxies to have lower extinction (Δ = 0.16 ± 0.06 mag). Using the extinction normalised by the stellar mass surface density as a proxy for the gas mass fraction, we find it to be larger for the void early spirals (by a 5%), especially in their outer regions (23% larger). This indicates the effect of the void environment on the transition stage from star forming to passive.

The mass in the Universe is distributed non-uniformly, originating the Large Scale Structure (LSS), characterised by clusters, filaments, walls and voids. Galaxies in voids are bluer, later type, less massive, and have slower evolution than galaxies in denser environments. The effect of the void environment on properties such as star formation rate (SFR) is still under discussion. We tackle this by estimating spatially-resolved SFR from extinction-corrected Halpha luminosities of 220 void galaxies from the CAVITY survey. These observations consist of optical integral field unit data cubes from the PMAS/PPaK spectrograph at Calar Alto Observatory. We measure the continuum-subtracted emission lines to obtain maps of SFR, specific star formation rate (sSFR) and extinction. We assess global properties and radial profiles up to 2 half-light radii. We compare with galaxies in filaments and walls from the CALIFA survey using the same methodology, building a control sample matched in morphology and stellar mass. We find no significant differences in SFR and sSFR, although void galaxies tend to have larger SFR, especially for early spirals. This effect is present for Sa galaxies at all galactocentric distances, and in the outer parts of late-type spirals, evidencing slower transition to quiescence and less evolved discs. Void late-type galaxies have lower extinction. Using extinction normalised by stellar mass surface density as a proxy for gas mass fraction, we find it larger for void early spirals, especially in outer regions. This indicates the effect of the void environment on the transition from star forming to passive.

Context. The gas-phase mass–metallicity relation (MZR) of galaxies shows a noticeable break in slope and an increased scatter at low stellar masses, suggesting that the physical processes governing chemical enrichment differ between dwarf and high-mass systems. Dwarf galaxies, in particular, are highly susceptible to both internal and environmental mechanisms due to their shallow potential wells. Aims. The primary aim of this work is to assess whether a single, universal MZR can describe dwarf galaxies across diverse large-scale environments, or whether systematic environmental variations emerge. To probe these, we examine the MZR and star formation rate (SFR) of dwarf galaxies with stellar masses in the range of 8.9 < log(M ★ /M ⊙ ) < 9.5. Methods. Using optical spectra from the Sloan Digital Sky Survey, we measured the fluxes of key emission lines via the pyPipe3D full spectral fitting pipeline. Aperture-corrected fluxes, along with multiple metallicity indicators and calibrations, were used to derive the MZR and the SFR for 353, 311, and 22 dwarf galaxies located in voids, filaments, and clusters, respectively. Results. We find a systematic variation in the MZR slope, steeper in voids (0.28 ± 0.03) and progressively flatter in clusters (0.17 ± 0.08), indicating a dependence of the MZR on the large-scale environment in this mass regime. When galaxies are separated by local density, no significant differences are observed between isolated and non-isolated dwarfs in voids. Isolated dwarf galaxies in filaments also exhibit properties similar to those of their counterparts in voids. However, non-isolated filament galaxies exhibit similar MZR slopes comparable to those of cluster dwarfs and flatter slopes than their counterparts in voids. Conclusions. We report both large- and local-scale environmental dependencies in the gas-phase metallicity and in the slope of the MZR for dwarf galaxies. Consistent with the general consensus on the pre-processing of galaxies in filaments, our results indicate that the influence of the local environment becomes increasingly significant within the filamentary regions of the cosmic web, affecting the chemical enrichment and star formation activity of low-mass systems. These findings further suggest that a portion of the scatter commonly observed in the MZR of dwarf galaxies arises from environmental effects.

We present a new age determination of 24 globular clusters (GCs) dynamically associated with the main accretion events experienced by the Milky Way (MW), as part of the Cluster Ages to Reconstruct the Milky Way Assembly (CARMA) project's effort to trace the Galaxy's assembly history. We used deep and homogeneous archival Hubble Space Telescope data, and applied the CARMA isochrone-fitting code to derive homogeneous estimates of age, metallicity, reddening, and distance modulus for systems dynamically associated with Gaia-Sausage-Enceladus (GSE), the Sagittarius dwarf galaxy (Sag), the Helmi streams (H99), and the Sequoia galaxy (Seq). These 24 new determinations are supplemented by 11 previously studied GSE clusters to construct the complete age-metallicity relation (AMR) of the GSE system. We find that each progenitor system describes a well-defined AMR, with a distinct slope and extent reflecting its individual star-formation efficiency and chemical enrichment history. By fitting analytical AMR models within a Markov chain Monte Carlo framework, we quantify the stellar mass and accretion time for each progenitor galaxy. This results in the first detailed merger tree obtained from strictly homogeneous chronological information, according to which the Low-energy-Kraken-Heracles (LKH) system is the first merger experienced by the MW that brought GCs in, followed by Sequoia, H99, GSE, and finally Sgr. The most significant events in terms of stellar mass are LKH, GSE, and Sgr, which together contribute a total of approximately 2.5 x 10^9 solar masses. This corresponds to more than 95

The Helmi streams are remnants of a dwarf galaxy that was accreted by the Milky Way and whose stars now form a distinct kinematic and chemical substructure in the Galactic halo. Precisely age-dating these typically faint stars of extragalactic origin has been notoriously difficult due to the limitations of using only spectroscopic data, interferometry, or coarse asteroseismic measurements. Using observations from NASA’s Transiting Exoplanet Survey Satellite, we report detailed asteroseismic modeling results for two of the brightest red giants within the Helmi streams, HD 175305 and HD 128279. By modeling the individual oscillation mode frequencies and the spectroscopic properties of both stars, we determine their fundamental properties including mass, radius, and age ( τ ). We report τ = 11.16 ± 0.91 Gyr for HD 175305 and τ = 12.52 ± 1.05 Gyr for HD 128279, consistent with previously inferred star formation histories for the Helmi streams and the differential chemical abundances between the two stars. With precise ages for individual stream members, our results reinforce the hypothesis that the Helmi streams’ progenitor must have existed at least 12 Gyr ago. Our results also highlight that the ages of metal-poor, α -enhanced red giants can be severely underestimated when inferred using global asteroseismic parameters instead of individual mode frequencies.

Context. A crucial aspect of galaxy evolution is the pace at which galaxies build up their mass. We can investigate this hierarchical assembly by uncovering and timing accretion events experienced by our Galaxy. Aims. In the Milky Way, accreted debris has been previously identified in the local halo, thanks to the advent of Gaia data. We aim to couple this dataset with advancements in colour-magnitude diagram (CMD) fitting techniques to characterise the building blocks of the Galaxy, based on their age and metallicity distributions. Here, we focus on the retrograde halo, specifically those of Thamnos and Sequoia. Methods. We conducted this study as part of the ChronoGal project by fitting the absolute CMDs (using CMDft.Gaia) of samples of stars associated with these sub-structures, extracted from a local 5D Gaia DR3 dataset. Comparing their derived age and metallicity distributions with those of the expected contamination, from the dominant Gaia Enceladus (GE) and low-energy (LE) in situ populations, we can unveil the stellar population signatures of the progenitors of Sequoia and Thamnos. Results. We show that both Thamnos and Sequoia have a metal-poor population ([Fe/H] similar to-2.5 to -1.5 dex) that is distinct from the expected contamination. Their age distributions offer us the ability to see the pace of the build-up of their progenitors. Half of the stars in Sequoia were formed by the look-back time of similar to 12(-0.3)(+0.3) Gyr. Thamnos appears slightly older, on average, and declines quickly, having formed half its stars at similar to 12.3(-0.3)(+0.3) Gyr. Compared to GE and the LE in situ populations, they formed half of their stars by 12.1(-0.1)(+0.1) Gyr and 12.9(-0.1)(+0.1) Gyr, respectively. Caution should be taken when interpreting the age distributions, especially that of Sequoia, due to the low number of stars, which can cause shifts to younger ages of up to similar to 1 Gyr. However, considering these potential shifts and the underlying contamination that is inherently difficult to remove completely, our results allow us to safely conclude that Thamnos, Gaia Enceladus, and Sequoia are all predominantly old and accreted at similar epochs, within similar to 1-2 Gyr of each other. Conclusions. We present, for the first time, the age distributions of the retrograde halo sub-structures: Sequoia and Thamnos. These have been derived from purely photometric data using CMD fitting techniques, which also provide metallicity distributions that successfully reproduce the results from spectroscopy, highlighting the applicability of CMDft.Gaia.

Context. Investigation of the formation, origin, and evolution of the dichotomy of the Milky Way's thin and thick disc components has been a focal point of research since it is key to understanding the formation of our Galaxy. One difficulty in this pursuit is that the populations defined based on their morphology or kinematics show a mix of chemically distinct populations. Age is then a key parameter to understand the disc evolution. Aims. We aim to derive age and metallicity distributions of the kinematic thick and thin discs in order to reveal details of the duration, intensity, and relation between the star formation episodes that led to the current kinematic thick-thin disc configuration. Methods. We applied the CMDft.Gaia pipeline based on a colour-magnitude diagram fitting technique to derive the dynamically evolved star formation history (deSFH) of the kinematically selected thin and thick discs. The analysis is based on Gaia DR3 data within a cylindrical volume centred on the Sun with a radius of 250 pc and a height of 1 kpc. Results. Our analysis shows that the kinematically selected thick disc is predominantly older than 10 Gyr and underwent a rapid metallicity enrichment through three main episodes. The first occurred over 12 Gyr ago, peaking at [Z/H] similar to-0.5 dex; the second was around 11 Gyr ago and caused a rapid increase in metallicity up to [Z/H]=0.0 and a broad spread in [alpha/Fe] from similar to 0.3 to solar values; and the third, just over 10 Gyr ago, reached super-solar metallicities. In contrast, the kinematic thin disc stars began forming about 10 Gyr ago, coinciding with the thick disc's star formation end, and is characterised by a super-solar metallicity and low [alpha/Fe]. The transition between the kinematic thick and thin discs aligns with the Milky Way's last major merger: the accretion of Gaia-Sausage-Enceladus (GSE). We also identify a small population of kinematically selected thin disc stars with high and intermediate-[alpha/Fe] abundances, slightly older than 10 billion years, indicating a kinematic transition from thick to thin disc during the Milky Way's high and intermediate- [alpha/Fe] phase. The kinematic thin disc's age-metallicity relation reveals overlapping star formation episodes with distinct metallicities, suggesting radial mixing in the solar neighbourhood, with the greatest spread around 6 Gyr ago. Additionally, we detect an isolated thick disc star formation event 6 Gyr ago at solar metallicity, and it coincides with the estimated first pericentre of the Sagittarius satellite galaxy.

We report, for the first time, the detection of a sample of quenched and isolated dwarf galaxies (with 8.9 $<$ log(M_ ⋆/M_ ⊙) $<$ 9.5) in the least dense regions of the cosmic web, including voids, filaments, and walls. These dwarfs have no neighboring galaxy within 1.0 Mpc in projected distance. Based on the full spectral fitting of their central spectra using Sloan Digital Sky Survey data, these galaxies are gas-deprived, while also exhibiting a stellar mass assembly very similar to dwarfs in the central regions of galaxy clusters. Furthermore, they have experienced no significant star formation in the past 2 Gyr. Additionally, analyses of r-band images from the Dark Energy Camera Legacy Survey have shown that these dwarf galaxies host a central nuclear star cluster (NSC). Detecting quenched, isolated dwarf galaxies in cosmic voids indicates that environmental factors are not the sole drivers of their quenching. Internal mechanisms, such as feedback from in situ star formation, which also contribute to the NSC formation, along with black holes or variations in the conditions around their formation, offer potential explanations for star formation suppression in these galaxies. These findings highlight the need for a significant revision in our understanding of baryonic physics, particularly concerning the formation and evolution of low-mass galaxies.

Context. The local stellar halo of the Milky Way is known to contain the debris from accreted dwarf galaxies and globular clusters in the form of stellar streams and over-densities in the space of orbital properties (e.g. integrals of motion). Aims. While several over-densities have been uncovered and characterised dynamically using Gaia data, their nature is not always clear. Especially for a complete understanding of the smaller halo substructures, the kinematic information from Gaia needs to be coupled with chemical information. Methods. In this work, we combine Gaia data with targeted high-resolution UVES spectroscopy of five small substructures that were recently discovered in the local halo, namely ED-2, -3, -4, -5, and -6 (the ED streams). We present the chemical abundances measured from our newly obtained UVES spectra (20 stars) and from archival UVES spectra (nine stars). We compared these with homogeneously derived abundances from archive spectra of 12 Gaia Enceladus (GE) stars. Results. The chemical abundances of all five substructures suggest that they are of accreted origin, except for two stars that present a high [alpha/Fe] at high [Fe/H] more in line with an in situ origin. All but ED-2 present a significant spread in [Fe/H] suggestive of a dwarf galaxy origin. ED-3 and ED-4 tend to exhibit a lower [alpha/Fe] compared to GE stars. As for ED-5 and ED-6, they are consistent with the GE chemical track and could be high-energy tails of GE that were lost earlier in the accretion process. We present new elemental abundances for five ED-2 stars, including more elements for the Gaia BH3 companion star. Our findings are in line with the picture that ED-2 is a disrupted ancient star cluster.

Aims. In this work, we report the serendipitous identification of an isolated merging dwarf system with a total stellar mass of M-star similar to 10(9.7) M-circle dot, located in the centre of a cosmic void. This system is one of the rare examples, and possibly the first, of merging dwarf galaxy pairs studied within the central region of a cosmic void. This system is remarkable due to its orientation relative to the line of sight and its unique local and large-scale environment. Methods. Using CAVITY PPAK-IFU data combined with deep optical broadband imaging from the Isaac Newton Telescope, we analysed the kinematics and ionised gas properties of each dwarf galaxy in the system by employing a full spectral fitting technique. Results. The orientation of this merging pair relative to the line of sight allowed us to determine the dynamical mass of each component, which we found to have similar dynamical masses within galactocentric distances of up to 2.9 kpc. These galaxies were likely star-forming dwarfs with rotating discs prior to the merger. While the gas-phase metallicity of both components is consistent with that of star-forming dwarf galaxies, the star formation rates observed in both components exceed those typically reported for equally massive star-forming dwarf galaxies. This indicates that the merger has presumably contributed to enhancing star formation. Our analysis shows no signs of AGN activity in this merging pair. Furthermore, we found no significant difference in the optical g-r colour of this merging pair compared to other merging dwarf pairs across different environments. Conclusions. While most merging events occur in group-like environments with a high galaxy density and the tidal influence of a host halo, and isolated mergers typically involve galaxies with significant mass differences, the identified merging pair does not follow these patterns. We speculate that the global dynamics of the void or past three-body encounters involving components of this pair and a nearby dwarf galaxy might have triggered this merging event.

Context . Gaia -Sausage-Enceladus is considered the last major merger that contributed to the formation of the Milky Way. Its remnants dominate the nearby accreted stellar halo of the Milky Way. Aims . We aim to characterise the star formation history of Gaia -Sausage-Enceladus through the age and metallicity of its stellar populations. Methods . From Gaia DR3 data, we dynamically defined three Gaia -Sausage-Enceladus samples with different criteria and possible degrees of contamination from other substructures in the halo. Then, we derived the stellar age and metallicity distributions using the CMDft. Gaia package. Results . We identified three main populations of stars and a fourth smaller one following an almost linear age-[M/H] relation. We associate the three oldest populations with the bulk of the star formation that lasted for, at least, ∼ 3−4 Gyr and ended about 10 Gyr ago, its metallicities ranging from −1.7 to −0.8. We categorise these populations into two main epochs: the evolution of GSE in isolation and the merger event. This separation finds independent support from the age-metallicity relation of GSE globular clusters. The fourth population is younger and more metal-rich, at ∼ 8.5 Gyr and [M/H] ∼−0.4; its link to GSE is unclear.

Context. Gaia-Sausage-Enceladus is considered the last major merger that contributed to the formation of the Milky Way. Its remnants dominate the nearby accreted stellar halo of the Milky Way. Aims. We aim to characterise the star formation history of Gaia-Sausage-Enceladus through the age and metallicity of its stellar populations. Methods. From Gaia DR3 data, we dynamically defined three Gaia-Sausage-Enceladus samples with different criteria and possible degrees of contamination from other substructures in the halo. Then, we derived the stellar age and metallicity distributions using the CMDft.Gaia package. Results. We identified three main populations of stars and a fourth smaller one following an almost linear age-[M/H] relation. We associate the three oldest populations with the bulk of the star formation that lasted for, at least, similar to 3-4 Gyr and ended about 10 Gyr ago, its metallicities ranging from -1.7 to -0.8. We categorise these populations into two main epochs: the evolution of GSE in isolation and the merger event. This separation finds independent support from the age-metallicity relation of GSE globular clusters. The fourth population is younger and more metal-rich, at similar to 8.5 Gyr and [M/H] similar to-0.4; its link to GSE is unclear.

We present the age determination of 13 globular clusters that are dynamically associated with the Gaia-Sausage-Enceladus (GSE) merger event, as part of the CARMA project's effort to trace the Milky Way assembly history. We used deep and homogeneous archival Hubble Space Telescope data, and applied isochrone fitting to derive homogeneous age estimates. We find that the majority of the selected clusters form a well-defined age-metallicity relation, with a few outliers. Among these, NGC 288 and NGC 6205 are more than 2 Gyr older than the other GSE globular clusters at a similar metallicity, and are therefore interpreted as probably having originated in situ. Moreover, NGC 7099 is somewhat younger than the average GSE trend, which suggests a possible alternative dwarf galaxy progenitor, while NGC 5286 is slightly older, as if its progenitor was characterised by greater star-formation efficiency. Another remarkable feature of the resulting age-metallicity relation is the presence of two epochs of globular cluster formation, with a duration of similar to 0.3 Gyr each and separated by similar to 2 Gyr. These findings are in excellent agreement with the age-metallicity relation recently found for halo field stars, which clearly hints at episodic star-formation in GSE. The age of the two formation epochs is similar to the mean age of the two groups of in-situ globular clusters previously studied by CARMA. These epochs might therefore precisely pinpoint two important dynamical events that Gaia-Sausage-Enceladus had with the Milky Way during its evolutionary history. Finally, we discuss the correlation between the recent spectroscopic determination of Si and Eu, and the clusters age and origin.

The Calar Alto Void Integral-field Treasury surveY (CAVITY) is a legacy project aimed at characterising the population of galaxies inhabiting voids, which are the most under-dense regions of the cosmic web, located in the Local Universe. This paper describes the first public data release (DR1) of CAVITY, comprising science-grade optical data cubes for the initial 100 out of a total of similar to 300 galaxies in the Local Universe (0.005 < z < 0.050). These data were acquired using the integral-field spectrograph PMAS/PPak mounted on the 3.5m telescope at the Calar Alto observatory. The DR1 galaxy sample encompasses diverse characteristics in the color-magnitude space, morphological type, stellar mass, and gas ionisation conditions, providing a rich resource for addressing key questions in galaxy evolution through spatially resolved spectroscopy. The galaxies in this study were observed with the low-resolution V500 set-up, spanning the wavelength range 3745-7500 angstrom, with a spectral resolution of 6.0 angstrom (FWHM). Here, we describe the data reduction and characteristics and data structure of the CAVITY datasets essential for their scientific utilisation, highlighting such concerns as vignetting effects, as well as the identification of bad pixels and management of spatially correlated noise. We also provide instructions for accessing the CAVITY datasets and associated ancillary data through the project's dedicated database.

We aim to investigate how the local environment influences the star formation history (SFH) of galaxies residing in various large-scale environments. We categorise a sample of 9384 galaxies into the three primary large scale structures (voids, walls & filaments, and clusters) and further classify them based on their local environment (as either "singlets" or group members), through a search of companion galaxies within sky-projected distances Δ r_p < 0.45 Mpc and velocity differences Δ v < 160 km s^-1. Subsequently, we explore these subsamples through SFH data from previous works. Throughout the study, galaxies are divided into long-timescale SFH galaxies (LT-SFH), which assemble their mass steadily along cosmic time, and short-timescale SFH galaxies (ST-SFH), which form their stars early. We then compare characteristic mass assembly look-back times. The distributions of mass assembly look-back times in ST-SFH galaxies are statistically different for singlets and groups. These differences are only found in LT-SFH galaxies when studying these distributions in stellar mass bins. Our results indicate that the large-scale environment is related to a delay in mass assembly of up to ∼2 Gyr, while this delay is <1 Gyr in the case of local environment. The effect of both kinds of environment is more significant in less massive galaxies, and in LT-SFHs. Our results are consistent with galaxies in groups assembling their stellar mass earlier than singlets, especially in voids and lower mass galaxies. Local environment plays a relevant role in stellar mass assembly times, although we find that large-scale structures also cause a delay in mass assembly, more so in the case of cluster galaxies.

The Universe is shaped as a web-like structure, formed by clusters, filaments, and walls that leave large volumes in between named voids. Galaxies in voids have been found to be of a later type, bluer, less massive, and to have a slower evolution than galaxies in denser environments (filaments and walls). However, the effect of the void environment on their stellar population properties is still unclear. We aim to address this question using 118 optical integral field unit datacubes from the Calar Alto Void Integral-field Treasury surveY (CAVITY), observed with the PMAS/PPaK spectrograph at the 3.5m telescope at the Calar Alto Observatory (Almería, Spain). We used the non-parametric full spectral fitting code STARLIGHT to estimate their stellar population properties: stellar mass, stellar mass surface density, age, star formation rate (SFR), and specific star formation rate (sSFR). We analysed the results through the global and spatially resolved properties. Then, we compared them with a control sample of galaxies in filaments and walls from the CALIFA survey, matched in stellar mass and morphological type. Key findings include void galaxies having a slightly higher half-light radius (HLR), lower stellar mass surface density, and younger ages across all morphological types, and slightly elevated SFR and sSFR (only significant enough for Sas). Many of these differences appear in the outer parts of spiral galaxies in voids (HLR > 1), which are younger and exhibit a higher sSFR, indicative of less evolved discs. This trend is also found for early-type spirals, suggesting a slower transition from star-forming to quiescent states in voids. Our analysis indicates that void galaxies, influenced by their surroundings, undergo a more gradual evolution, especially in their outer regions, with a more pronounced effect for low-mass galaxies.

We obtain a quantitative star formation history (SFH) of a shell-like structure ('shell') located in the northeastern part of the Small Magellanic Cloud (SMC). We use the Survey of the MAgellanic Stellar History to derive colour-magnitude diagrams (CMDs), reaching below the oldest main-sequence turnoff, from which we compute the SFHs with CMD-fitting techniques. We present, for the first time, a novel technique that uses red clump (RC) stars from the CMDs to assess and account for the SMC's line-of-sight depth effect present during the SFH derivation. We find that accounting for this effect recovers a more accurate SFH. We quantify an similar to 7 kpc line-of-sight depth present in the CMDs, in good agreement with depth estimates from RC stars in the northeastern SMC. By isolating the stellar content of the northeastern shell and incorporating the line-of-sight depth into our calculations, we obtain an unprecedentedly detailed SFH. We find that the northeastern shell is primarily composed of stars younger than similar to 500 Myr, with significant star formation enhancements around similar to 250 and similar to 450 Myr. These young stars are the main contributors to the shell's structure. We show synchronicity between the northeastern shell's SFH with the Large Magellanic Cloud's (LMC) northern arm, which we attribute to the interaction history of the SMC with the LMC and the Milky Way (MW) over the past similar to 500 Myr. Our results highlight the complex interplay of ram pressure stripping and the influence of the MW's circumgalactic medium in shaping the SMC's northeastern shell.