arXiv subjects

Laia Casamiquela

Publications and source records attributed to Laia Casamiquela.

16 recordsLinked to original sources

arXiv2026

CosmoDyn: a semi-analytic post-processing framework for the dynamical evolution of compact stellar systems and black holes in cosmological simulations

Although a large number of cosmological simulations are now publicly available, their spatial and mass resolutions remain insufficient to accurately follow the dynamics of compact stellar systems and black holes. A complementary approach is therefore required to exploit the cosmological assembly histories encoded in these simulations without rerunning them. We present CosmoDyn, an open-source Python framework that reconstructs time-dependent galactic environments from any cosmological simulations and explicitly follows unresolved compact objects within them. A distinctive feature of CosmoDyn is that it models not only the main host galaxy but also its accreted satellites via moving gravitational potentials. The framework can therefore account simultaneously for the delivery of ex-situ populations and for the dynamical influence of satellites on in-situ population already present in the host. The modular pipeline comprises four main stages: reconstructing the evolving host and satellite potentials; generating in-situ and ex-situ populations of compact objects; integrating their orbits with configurable prescriptions for dynamical friction, and mass loss; and modeling tidal streams. Once reconstructed, the same cosmological environment can be reused to explore different objects, initial conditions, and physical prescriptions at low computational cost. CosmoDyn thus enables rapid parameter exploration and applications to statistically significant galaxy samples, while its modular architecture is designed to incorporate progressively more realistic potentials, and formation models.

astro-ph.GA↗

arXiv2026

Stellar Population Astrophysics (SPA) with the TNG. Beyond the iron peak: Galactic evolution of molybdenum, ruthenium and zirconium through open clusters

Context: Open clusters serve as key laboratories for studying the chemical evolution of the Milky Way. In particular, leveraging these coeval groups of stars to study elements beyond the iron peak provides insights into heavy-element nucleosynthesis, whose origins remain uncertain. Aims: This work aims to determine the Mo, Ru, and Zr abundances for 81 stars across 30 open clusters. We compare these new chemical patterns with those of key reference elements (Y, Sr, Eu), which were previously derived by our group. This comparison seeks to disentangle the distinct contributions from various nucleosynthetic processes. Methods: Using the high-resolution spectra acquired within the Stellar Population Astrophysics programme using the HARPS-N echelle spectrograph at the Telescopio Nazionale Galileo, we estimate chemical abundances through spectral synthesis with TSFitPy under local thermodynamic equilibrium (LTE) conditions. Results: This study provides the first Ru abundances for a large open cluster sample, alongside new measurements for Mo and Zr. We observe tight correlations between Mo, Ru, and other s-process elements (Sr, Y, Zr), with slopes near unity, suggesting common enrichment timescales. Conversely, relations with the r-process element Eu show significant deviations, implying additional nucleosynthetic contributions. Crucially, chemical planes involving [Mo/Ru] and [s/Mo] ratios suggest systematic offsets when compared to theoretical s-process predictions.

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arXiv2026

Unveiling the Milky Way with a Gaia DR3 census of OB-type stars within 2 kpc. I. Tracing local Galactic structure, massive star-forming regions and core-collapse supernova progenitors

O- and B-type stars are young and hot, thereby serving as vital tracers of the star formation and spiral arm structure of the Milky Way. At the dusk of the \textit{Gaia} DR3 era, a high-confidence and accurate catalogue appears timely. Here we have characterized a population of 105,971 OB-type stars (T$_{\rm eff} >$ 10,000 K; hereafter OB stars) within 2 kpc from the Sun, using an astro-photometric Bayesian inference tool. Our resulting map unveils a complex view of the young stellar populations across the thin disk, with prominent large-scale features such as the Cepheus Spur, the Giant Oval Cavity, and a segment of the Sagittarius-Carina spiral arm all visible. Their inhomogeneous spatial distribution implies that massive star formation has taken place clustered across a few highly concentrated regions. We find a correlation between the overdensities of OB stars and young open clusters ($<$20 Myr), although OB stars can be better detected in high-extinction regions. We identify over 4200 OB stars as core-collapse supernova (ccSN) or direct-collapse black hole (BH) progenitor candidates, and therefore targets of interest for spectroscopic follow-up. Furthermore, we find no OB-type star ccSN progenitor to explode within the next 1 Myr within 100 pc, at which such an event could be harmful to Earth's biosphere. Finally, we identify more BH progenitors to collapse within the next 1 Myr than ccSN to explode, despite the former's much scarcer number - which could be indicative of a recent massive star formation burst in the local Milky Way.

astro-ph.GA↗

arXiv2026

Stellar masses and ages in Gaia Data Release 4 from the Final Luminosity Age Mass Estimator algorithm

The masses and ages of stars are key quantities for understanding exoplanetary, stellar, and galactic evolution. In the context of Gaia, these parameters provide insights into the stellar populations, helping to trace the formation and history of the Galaxy. As part of the Gaia Data Processing and Analysis Consortium (DPAC), the Final Luminosity Age Mass Estimator (FLAME) pipeline processes Gaia data to derive stellar parameters comprising luminosities, radii, masses and ages. This paper discusses the methods and data used in FLAME for Gaia Data releases and the expected performances of FLAME for the 4th Gaia Data Release. FLAME comprises two main components: the first one, which is analytical, is used to estimate luminosity, radius, and radial velocity correction due to gravitational redshift by exploiting the atmospheric, astrometric, and photometric parameters produced within Gaia. The second is a model inference based on two main approaches: a classical minimization approach, and a Bayesian framework. It aims to derive mass, age, and evolutionary stage. The two step implementation offers flexibility in handling photometric properties that are prone to systematic errors. Tests with simulated data, the Sun, and well characterised samples of stars show that the methods in FLAME perform as expected, producing results in statistical agreement with the literature. We provide new stellar fundamental parameters for some high velocity stars, stars with very low mass companions, and a selection of stars in the Plato Field of View. In Gaia Data Release 4 approximately 500 million sources will have results from the pipeline. [abridged]

astro-ph.SR↗

arXiv2026

Bar-induced deflection of open cluster tidal tails

We present a systematic study of how the Galactic bar affects the orientation of tidal tails of open clusters and assess the power of tail morphology to constrain the bar's pattern speed. Using test-particle simulations, we follow the evolution of $\sim 1450$ observed open clusters from the Hunt & Reffert (2024) catalogue in an axisymmetric reference potential and in eight barred potentials with pattern speeds ranging from $Ω_b = 20$ km/s/kpc to $Ω_b = 55$ km/s/kpc. We quantify the bar effect through the deflection angle -- the rotation of the tail orientation in the barred model relative to the axisymmetric case. The deflection angle varies systematically with bar pattern speed and cluster guiding radius. The largest deflections occur for clusters near the outer Lindblad resonance (OLR), with the sign of the angle set by the orientation of the orbit's pericentre relative to the bar's major axis. For each cluster we measure the distance from the centre beyond which different bar models produce distinguishable tail orientations, and classify each cluster as bar-sensitive or bar-insensitive based on its maximum absolute deflection across the bar models. Comparing with observed tidal tails from the literature, we find that the extended tails of NGC 2632 and the Hyades disfavour moderate pattern speeds. We provide a catalogue of deflection angles, minimal tail extents, and bar-sensitivity flags to guide future observational searches and the re-assessment of existing tidal tail catalogues.

astro-ph.GA↗

arXiv2026

A new Gaia census of OB associations within 1 kpc

OB associations are primordial tracers of star formation and Galactic structure. Originally defined about 80 years ago, their historical membership lists have been superseded thanks to the precise astrometry from ESA's \textit{Gaia}'s satellite. Recent studies have however been mostly focused on individual OB associations or limited by the coverage of spectroscopic surveys. In this paper, we exploit a complete census of $\sim$25,000 O- and B-type stars within 1 kpc of the Sun to produce a highly-reliable catalogue of 56 OB associations using the HDBSCAN clustering algorithm, increasing the number of known OB associations by a factor of two within this volume. We assess the validity of this catalogue by crossmatching our OB association members with other catalogues of OB associations, star clusters and young stellar groups, confirming the high-confidence of our census of OB associations. We characterize these OB associations physically (total initial stellar mass, number of OB stars, ...) and kinematically (velocity dispersion, linear expansion ages, ...). The majority of the OB associations (38 out of 56) exhibit a significant expansion pattern in at least one direction, including 12 in both plane-of-the-sky directions, though differences in expansion velocity suggest anisotropical expansion patterns. We compare the locations of these OB associations with superclouds and features in the local Milky Way such as the Radcliffe Wave and discuss the implications for star formation in the solar neighbourhood.

astro-ph.GA↗

arXiv2026

Gaia FGK Benchmark Stars: Impact of Spectral Resolution on Stellar Abundances

In the era of large Milky Way spectroscopic surveys, calibrating and standardizing stellar parameters and abundance measurements is crucial. The Gaia benchmark stars (GBS) are key references points characterized by well-defined parameters derived from fundamental relations independent of spectroscopy. We analyze 30 GBS with spectra data at three different resolutions. Our goal is to evaluate the impact of spectral resolution on the measurements of the stellar parameters and chemical abundances. We also present a line selection suitable for both metal-poor and metal-rich stars. We used R~190000 (R190), R~42000 (R42), R~28 000 (R28), and R190 degraded to R28 (R190-R28) spectral data to measure abundances with synthetic fitting and equivalent widths (EW) methods, testing the needed resolution to obtain consistent results. Our comparative analysis between R28 and R190-R28 shows that gaps in wavelength coverage can lead to discrepancies in the derived stellar parameters, particularly log g. These effects are not primarily driven by resolution, but rather by the limited spectral coverage and line availability. We find overall similar abundance, emphasizing the importance of line selection for spectroscopic studies. However, some elements (e.g, Ti II, Sc II) show larger discrepancies, possibly due to blending that becomes more pronounced as resolution decreases or is HFS-sensitive. Our comparative analysis shows that the abundances for Fe I, Ni I, Ti I, and Si I present less scatter across all resolutions, including R28. Our findings indicate that for some elements, synthetic fitting and the EW method give similar abundances, especially at the highest resolution. However, we also find that the highest resolution is not always essential for chemical abundance measurements. Our results provide practical guidelines for upcoming large surveys to reconstruct the chemical history of the Milky Way.

astro-ph.SR↗

arXiv2026

The high-altitude, inner-disc, and chemically peculiar open cluster UBC 1052

Out of all the discovered open clusters (OCs) that are located in the inner part of the Galaxy, only a small fraction has been observed with high-resolution spectroscopy. An intriguing population of inner-disc OCs at relatively high altitudes ($Z$) from the Galactic plane remains poorly studied. There are few reliable detections of such OCs, and their occurrence rate, dynamical origin and survival mechanism remain uncertain. We perform a detailed spectroscopic analysis of UBC 1052, located at a cylindrical galactocentric radius $R_{GC} = 6.1$ kpc and $Z = 340$ pc, which stands out as the oldest and highest-|$Z$| inner-disc OC studied at high resolution to date. We used FLAMES/VLT to acquire high signal-to-noise ratio UVES spectra of four red clump (RC) members ($G\sim14$ mag). From them we derived high-precision radial velocities ($v_{r}$) and local thermodynamic equilibrium chemical abundances for 23 elements through a strict line-by-line differential analysis, achieving a median precision in [X/H] of $\simeq0.06$ dex for each star. The four RC stars have fully compatible chemical abundances, with [X/H] dispersions among them <$0.03$ dex for 20 elements. We also acquired GIRAFFE spectra of other candidate members and derived their $v_{r}$. We find that UBC 1052 has an age of $2.25\pm0.25$ Gyr, a distance of $3.11\pm0.07$ kpc, an extinction $A_{V} =1.23$ mag, a mean radial velocity of $34.0\pm0.6$ $km$ ${s}^{-1}$, and a slightly super-solar [Fe/H] = $0.05\pm0.01$ dex. Such relatively low [Fe/H] at its $R_{GC}$ suggests that UBC 1052 is a rare candidate for an inward-migrated OC in the inner disc. Its detailed abundance pattern (e.g. [Ba/Zr] and [Nd/Y]) shows some interesting features that appear to be unique in the current census of OCs studied at high resolution, making it an interesting object for potential strong chemical-tagging searches for already dispersed member stars. [Abridged]

astro-ph.GA↗

arXiv2026

Gaia FGK Benchmark Stars: Selecting Infrared Lines for Abundance Determination

The advent of new and more powerful infrared spectrographs has significantly motivated the advancement of the study of atomic and molecular line lists and stellar atmosphere models. While optical abundance determinations rely on extensively validated line lists and modeling frameworks, infrared measurements still face larger uncertainties, largely driven by the choice of atmospheric models and the quality of the available atomic data. In this work, we aim to deliver a homogeneous and reproducible set of atomic absorption lines in the Y, J, and H bands (9800 - 18000 (Angstrom)), based exclusively on laboratory atomic data. We analyse CRIRES spectra of six Gaia FGK Benchmark Stars spanning a wide range in effective temperature, surface gravity, and chemical composition. Synthetic spectra are computed using the benchmark stellar parameters, and each transition is evaluated independently in every star through a quantitative sequence that examines line depth, saturation, blending (purity), and the agreement between observed and synthetic line profiles. We identify a set of robust atomic transitions in these bands that remain consistent across the full range of stellar parameters represented in our sample. Lines of alpha-elements such as Mg I, Si I, and Ca I, together with several Fe I transitions, satisfy all robustness criteria. Among the neutron-capture species explored, only Sr II provides lines that consistently meet our requirements. Beyond the specific list of accepted transitions, this study demonstrates that a fully quantitative, multi-criteria framework provides a transparent and reproducible foundation for near-infrared line validation as laboratory data, stellar atmosphere models, and instrumentation continue to improve.

astro-ph.SR↗

arXiv2025

The chemical enrichment histories across the Milky Way disk

The variation of metal production over time and its dilution in the interstellar medium depend on the star formation and gas accretion rates. Measuring age-chemistry relations across the Milky Way disk provides key constraints on the gas accretion and star formation histories, and offers insight into the birth locations of stars. We present a study based on a sample of nearly 30000 dwarf stars from the APOGEE DR17 survey within 2 kpc of the Sun, for which we measure accurate ages. Various parameter combinations are tested to optimize stellar age determination from isochrones. The resulting age-chemistry relations for a selected subsample of 12000 stars are interpreted with the aid of a chemical evolution model. The data reveal a well-defined, tight thick disk sequence, characterized by high [alpha/Fe], subsolar metallicities, and ages older than 8 Gyr. The thin disk, with lower [alpha/Fe] and younger ages, exhibits a wide spread in metallicity at all ages, with apparent structures. Dividing the sample by guiding radius into inner, intermediate, and outer disks shows distinct chemical evolution patterns. The inner disk displays a monotonic, homogeneous chemical evolution with little dispersion, while the outer disk shows little metallicity increase over the past 8 Gyr. The solar neighborhood appears as a mixture, not only due to stellar migration but also because the chemical evolution of the ISM in this intermediate region results from the mixing of gas from the inner and outer disks. In particular, we demonstrate that the solar vicinity experienced a decrease in the mean ISM metallicity 7-9 Gyr ago. A plausible explanation involves a radial inflow of lower-metallicity gas from the outer disk at that time, which diluted the gas leftover by the thick disk formation, contributing to the observed metallicity gradient in the intermediate region.

astro-ph.GA↗

arXiv2024

Abundance ties: Nephele and the globular cluster population accreted with $ω$ Cen. Based on APOGEE DR17 and Gaia EDR3

The peculiar Galactic globular cluster $ω$ Centauri (NGC 5139) has drawn attention for its unique features - such as a high stellar mass and a broad distribution of chemical elements - that have led to the hypothesis that it might be the nuclear remnant of an ancient dwarf galaxy accreted by the Milky Way (MW), potentially bringing along its own globular cluster (GC) system. In this work, we adopt an innovative approach by examining the individual chemical abundances of Galactic GCs. Applying Gaussian Mixture Models to globular cluster stars, whose membership is based on Gaia EDR3, and whose chemical abundances are provided by APOGEE DR17, we depart from traditional kinematic-based procedures and search for GCs that are chemically compatible with $ω$ Cen in a 8-dimensional space defined by [Fe/H], [Mg/Fe], [Si/Fe], [Ca/Fe], [C/Fe], [Al/Fe], [K/Fe], and [Mn/Fe]. Our analysis leads to the identification of six GCs - NGC 6752, NGC 6656, NGC 6809, NGC 6273, NGC 6205, and NGC 6254 - that exhibit strong chemical similarities with $ω$ Cen, and which have metallicities that coincide with those of the two main peaks of $ω$ Cen's metallicity distribution. The chemical patterns of these clusters lead to the exclusion that they formed in progenitor galaxies with chemical enrichment histories similar to those of the Large and Small Magellanic Clouds, Sagittarius, and Fornax. Once placed in kinematic spaces such as the energy - angular momentum plane, these GCs result scattered across an extended region, which is predicted by N-body simulations if their common progenitor was sufficiently massive compared to the MW. Our novel approach suggests a common origin for NGC 6752, NGC 6656, NGC 6809, NGC 6273, NGC 6205, NGC 6254 and $ω$ Cen, indicating that Nephele, as we propose to call the progenitor in which these GCs formed, played a substantial role in the Galaxy's history.

astro-ph.GA↗

arXiv2023

The wide-field, multiplexed, spectroscopic facility WEAVE: Survey design, overview, and simulated implementation

WEAVE, the new wide-field, massively multiplexed spectroscopic survey facility for the William Herschel Telescope, will see first light in late 2022. WEAVE comprises a new 2-degree field-of-view prime-focus corrector system, a nearly 1000-multiplex fibre positioner, 20 individually deployable 'mini' integral field units (IFUs), and a single large IFU. These fibre systems feed a dual-beam spectrograph covering the wavelength range 366$-$959\,nm at $R\sim5000$, or two shorter ranges at $R\sim20\,000$. After summarising the design and implementation of WEAVE and its data systems, we present the organisation, science drivers and design of a five- to seven-year programme of eight individual surveys to: (i) study our Galaxy's origins by completing Gaia's phase-space information, providing metallicities to its limiting magnitude for $\sim$3 million stars and detailed abundances for $\sim1.5$ million brighter field and open-cluster stars; (ii) survey $\sim0.4$ million Galactic-plane OBA stars, young stellar objects and nearby gas to understand the evolution of young stars and their environments; (iii) perform an extensive spectral survey of white dwarfs; (iv) survey $\sim400$ neutral-hydrogen-selected galaxies with the IFUs; (v) study properties and kinematics of stellar populations and ionised gas in $z<0.5$ cluster galaxies; (vi) survey stellar populations and kinematics in $\sim25\,000$ field galaxies at $0.3\lesssim z \lesssim 0.7$; (vii) study the cosmic evolution of accretion and star formation using $>1$ million spectra of LOFAR-selected radio sources; (viii) trace structures using intergalactic/circumgalactic gas at $z>2$. Finally, we describe the WEAVE Operational Rehearsals using the WEAVE Simulator.

astro-ph.IM↗

arXiv2023

Gaia FGK Benchmark Stars: fundamental Teff and log g of the third version

Context. Large spectroscopic surveys devoted to the study of the Milky Way, including Gaia, use automated pipelines to massively determine the atmospheric parameters of millions of stars. The Gaia FGK Benchmark Stars are reference stars with Teff and log g derived through fundamental relations, independently of spectroscopy, to be used as anchors for the parameter scale. The first and second versions of the sample have been extensively used for that purpose, and more generally to help constrain stellar models. Aims. We provide the third version of the Gaia FGK Benchmark Stars, an extended set intended to improve the calibration of spectroscopic surveys, and their interconnection. Methods. We have compiled about 200 candidates which have precise measurements of angular diameters and parallaxes. We determined their bolometric fluxes by fitting their spectral energy distribution. Masses were determined using two sets of stellar evolution models. In a companion paper we describe the determination of metallicities and detailed abundances. Results. We provide a new set of 192 Gaia FGK Benchmark Stars with their fundamental Teff and logg, and with uncertainties lower than 2% for most stars. Compared to the previous versions, the homogeneity and accuracy of the fundamental parameters are significantly improved thanks to the high quality of the Gaia data reflecting on distances and bolometric fluxes.

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arXiv2022

Chemically Peculiar Stars in the Open Cluster Stock 2

The recently re-discovered open cluster Stock 2, located roughly 375 pc away and about 400 Myr old, has the potential to be an exciting new testbed for our understanding of stellar evolution. We present results from a spectroscopic campaign to characterize stars near the cluster's main-sequence turnoff; our goal is to identify candidate chemically peculiar stars among the cluster's A stars. We obtained echelle spectra for 64 cluster members with ESPaDOnS on the 3.6-m Canada-France-Hawaii Telescope, Mauna Kea Observatory, USA, and for six stars with SOPHIE on the 1.93-m telescope at the Observatoire de Haute-Provence, France. We complemented these new observations with those of 13 high-mass cluster members from the HARPS-N archive; our overall sample is of 71 stars. We derived the fundamental parameters (Teff, log g, [M/H]) as well as vsini for our sample using the Sliced Inverse Regression (SIR) technique, and then used iSpec to derive individual abundances of 12 chemical species. With these abundance determinations, we identified nine A stars with anomalous levels of Sc, Ca, and other metallic lines. Follow-up observations of these Am candidates with a known age can transform them into benchmarks for evolutionary models that include atomic diffusion and help build a better understanding of the complex interactions between macroscopic and microscopic processes in stellar interiors.

astro-ph.SR↗

arXiv2021

Assessment of [Fe/H] determinations for FGK stars in spectroscopic surveys

The number of stars with a measured value of [Fe/H] is considerably increasing thanks to spectroscopic surveys. However different methodologies, inputs and assumptions used in spectral analyses lead to different precisions in [Fe/H] and possibly to systematic differences that need to be evaluated. It is essential to understand the characteristics of each survey to fully exploit their potential, in particular if the surveys are combined. The purpose of this study is to compare [Fe/H] determinations from the largest spectroscopic surveys (APOGEE, GALAH, the Gaia ESO survey, RAVE, LAMOST, SEGUE ) to other catalogues taken as reference. Offsets and dispersions of the residuals are examined as well as their trends with other parameters. We use reference samples providing independent determinations of [Fe/H] which are compared to those from the surveys for common stars. The distribution of the residuals is assessed through simple statistics that measures the offset between two catalogues and the dispersion representative of the precision of both catalogues. When relevant, linear fits are performed. A large sample of FGK-type stars with [Fe/H] based on high-resolution, high signal to noise spectroscopy was built from the PASTEL catalogue to provide a reference sample. We also use FGK members in open and globular clusters to assess the internal consistency of [Fe/H] of each survey. The agreement of median [Fe/H] values for clusters observed by different surveys is discussed. All the surveys overestimate the low metallicities, and some of them also underestimate the high metallicities. They perform well in the most populated intermediate metallicity range, whatever the resolution. In most cases the typical precision that we deduce from the comparisons is in good agreement with the uncertainties quoted in the catalogues. Some exceptions to this general behaviour are discussed.

astro-ph.SR↗

arXiv2021

The consistency of chemical clocks among coeval stars

The abundance ratios of some chemical species have been found to correlate with stellar age, leading to the possibility of using stellar atmospheric abundances as stellar age indicators. These chemical clocks have been calibrated with solar-twins, open clusters and red giants, but it remains to be seen whether they can be effective at identifying coeval stars in a field population that spans a broad parameter space (i.e., the promise of chemical tagging). Since the components of wide binaries are known to be stars of common origins, they constitute ideal laboratories for testing the usefulness of chemical clocks for the age dating of field stars. We determined the abundances of a new sample of 5 binaries and collected data for other 31 systems from the literature in order to test the applicability of chemical clocks. We recover the well known result that the components of wide binaries have more consistent chemistry than that of random pairs. However, we also show for the first time that abundance ratios designed as chemical clocks are even more consistent among the components of wide binaries than their [X/Fe] ratios. Not only that, but the special case of the pair HIP 34426/HIP 34407 may indicate that chemical clocks are consistent for coeval stars even when the individual abundances are not. If the assumption that chemical clocks are reliable age indicators is correct, this would constitute first quantitative, statistically significant evidence that the components of wide binaries in the Galactic field are indeed coeval, validating a large body of published work that relies on that to be the case. Moreover, our results provide strong evidence that chemical clocks indeed carry important information about stellar birthplaces and chemical evolution, and thus we propose that including them in chemical tagging efforts may facilitate the identification of nowadays dissolved stellar groups.

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