Star Clusters Research Articles

Inconsistent metallicity spreads in first-generation stars of globular clusters from high-resolution spectroscopy and HST photometry

Inconsistent metallicity spreads in first-generation stars of globular clusters from high-resolution spectroscopy and HST photometry

Empirical SED Templates for Star Clusters Observed with HST and JWST: No Strong PAH or IR Dust Emission after 5 Myr

Empirical SED Templates for Star Clusters Observed with HST and JWST: No Strong PAH or IR Dust Emission after 5 Myr

Beyond the Goldilocks Zone: Identifying Critical Features in Massive Black Hole Formation

Abstract Most galaxies, including the Milky Way, host a supermassive black hole (SMBH) at the center. These SMBHs can be observed out to high redshifts (z ≥ 6) if the accretion rate is sufficiently large. However, we do not fully understand the mechanism through which these black holes form at early times. The heavy (or direct collapse) seeding mechanism has emerged as a probable contender in which the core of an atomic cooling halo directly collapses into a dense stellar cluster that could host supermassive stars that proceed to form a black hole seed of mass ∼ 105 M ⊙. We use the Renaissance Simulations to investigate the properties of 35 direct collapse black hole (DCBH) candidate host halos at z = 15–24 and compare them to noncandidate halos. We aim to understand what features differentiate halos capable of hosting a DCBH from the general halo population with the use of statistical analysis and machine learning methods. We examine 18 halo, central, and environmental properties. We find that DCBH candidacy is more dependent on a halo’s core internal properties than on exterior factors such as Lyman–Werner (LW) flux and distance to the closest galaxy; our analysis selects density and radial mass influx as the most important features (outside candidacy establishing features). Our results concur with the recent suggestion that DCBH host halos neither need to lie within a “Goldilocks zone” nor have a significant amount of LW flux to suppress cooling. This paper presents insight to the dynamics possibly occurring in potential DCBH host halos and seeks to provide guidance to DCBH subgrid formation models.

Study of open star clusters using the Gaia DR3: I-poorly studied King 2 and King 5

Abstract In this study, we utilize photometric and kinematic data from Gaia DR3 and the ASteCA package to analyze the sparsely studied open clusters, King 2 and King 5. For King 2, we identify 340 probable members with membership probabilities exceeding 50%. Its mean proper motion components are determined as (μα cosδ, μδ) = (−1.407 ± 0.008, −0.863 ± 0.012) mas yr-1, and its limiting radius is derived as 6.94 +0.22 −1.06 arcminutes based on radial density profiles. The cluster has an estimated age of 4.80 ± 0.30 Gyr, a distance of 6586 ± 164 pc, and a metallicity of [Fe/H] = -0.25 dex (z = 0.0088). We detect 17 blue straggler stars (BSSs) concentrated in its core, and its total mass is estimated to be 356 ± 19 M⊙. The computed apex motion is (Ao, Do) = (−142o. 61 ± 0o. 08, −63o. 58 ± 0o. 13). Similarly, King 5 consists of 403 probable members with a mean proper motion components (μα cosδ, μδ) = (−0.291 ± 0.005, −1.256 ± 0.005) mas yr-1 and a limiting radius of 11.33+5.45 −2.16 arcminutes. The cluster’s age is determined as 1.45 ± 0.10 Gyr, with a distance of 2220 ± 40 pc and a metallicity of [Fe/H] = -0.15 dex (z = 0.0109). We identify 4 centrally concentrated BSSs, and the total mass is estimated as 484±22 M⊙. The apex motion is calculated as (Ao, Do) = (−115o. 10 ± 0o. 09, −73o. 16 ± 0o. 12). Theorbital analysis of King 2 and King 5 indicates nearly circular orbits, characterized by low eccentricities and minimal variation in their apogalactic and perigalactic distances. King 2 and King 5 reach maximum heights of 499 ± 25 pc and 177 ± 2 pc from the Galactic plane, respectively, confirming their classification as young stellar disc population.

MAGICS. III. Seeds Sink Swiftly: Nuclear Star Clusters Dramatically Accelerate Seed Black Hole Mergers

Abstract Merger rate predictions of massive black hole (MBH) seeds from large-scale cosmological simulations differ widely, with recent studies highlighting the challenge of low-mass MBH seeds failing to reach the galactic center, a phenomenon known as the seed sinking problem. In this work, we tackle this issue by integrating cosmological simulations and galaxy merger simulations from the MAGICS-I and MAGICS-II resimulation suites with high-resolution N-body simulations. Building on the findings of MAGICS-II, which showed that only MBH seeds embedded in stellar systems are able to sink to the center, we extend the investigation by incorporating nuclear star clusters (NSCs) into our models. Utilizing N-body resimulations with up to 107 particles, we demonstrate that interactions between NSCs and their surrounding galactic environment, particularly tidal forces triggered by cluster interactions, significantly accelerate the sinking of MBHs to the galactic center. This process leads to the formation of a hard binary in ≲500 Myr after the onset of a galaxy merger. Our results show that in eight out of 12 models, the high stellar density of the surrounding NSCs enhances MBH hardening, facilitating gravitational-wave mergers by redshift z = 4. We conclude that at z > 4, dense NSCs serve as the dominant channel for MBH seed mergers, producing a merger rate of 0.3–0.6 yr−1 at z = 4, which is approximately 300–600 times higher than in non-NSC environments. In contrast, in environments without NSCs, surrounding dark matter plays a more significant role in loss-cone scattering.

Testing Cluster Membership of Planetary Nebulae with High-precision Proper Motions. II. HST Observations of PHR J1315–6555 in the Open Cluster AL 1 (ESO 96-SC04)

Abstract Planetary nebulae (PNe) shown to be members of star clusters provide information on their properties and evolutionary histories that cannot be determined for PNe in the field, in particular the initial masses of their progenitor stars. Here we investigate the bipolar PN PHR J1315−6555 (hereafter PHR J1315), which lies near the open cluster AL 1 (ESO 96-SC04) on the sky. Previous work has established that the PN and cluster have similar radial velocities and amounts of interstellar reddening, and similar distances estimated using independent methods. We have obtained new images of the PN and cluster using the Hubble Space Telescope (HST). Combined with archival HST frames taken 12 yr earlier, they provide high-precision proper motions (PMs) for two candidate central stars of PHR J1315. We find that the PMs of both candidates are consistent with those of cluster members, strongly confirming the PN’s membership in AL 1. The candidate lying closer to the center of PHR J1315 has the color and luminosity of an early F-type dwarf, suggesting that it may be the optical primary in a close post-common-envelope binary. We used the HST data to construct a color–magnitude diagram for AL 1, which we corrected for significant foreground differential reddening. Isochrone fitting reveals that the cluster lies at a remarkably large distance of about 13 kpc, and has an age of about 1.0 Gyr. The initial mass of the progenitor of PHR J1315 was about 2.1 M ⊙. We suggest follow-up investigations that would provide tighter constraints on the object’s evolution.

Identification of a Turnover in the Initial Mass Function of a Young Stellar Cluster Down to 0.5 MJ

Abstract A successful theory of star formation should predict the number of objects as a function of their mass produced through star-forming events. Previous studies in star-forming regions and the solar neighborhood have identified a mass function increasing from the hydrogen-burning limit down to about 10 M J. Theory predicts a limit to the fragmentation process, providing a natural turnover in the mass function down to the opacity limit of turbulent fragmentation, thought to be near 1–10 M J. Programs to date have not been sensitive enough to probe the hypothesized opacity limit of fragmentation. We present the first identification of a turnover in the initial mass function below 12 M J within NGC 2024, a young star-forming region. With JWST/NIRCam deep exposures across 0.7–5 μm, we identified several free-floating objects down to roughly 3 M J with sensitivity to 0.5 M J. We present evidence for a double power-law model increasing from about 60 M J to roughly 12 M J, consistent with previous studies, followed by a decrease down to 0.5 M J. Our results support the predictions of star and brown dwarf formation theory, identifying the theoretical turnover in the mass function and suggesting the fundamental limit of turbulent fragmentation to be near 3 M J.

New probe of dark matter-baryon interactions in compact stellar systems

We investigate the astrophysical consequences of an attractive long-range interaction between dark matter and baryonic matter. Our study highlights the role of this interaction in inducing dynamical friction between dark matter and stars, which can significantly influence the evolution of compact stellar systems. Using the star cluster in Eridanus II as a case study, we derive a new stringent upper bound on the interaction strength α˜≤314.5 for the interaction range λ=1 pc. This constraint is independent of the dark matter mass and can improve the existing model-independent limits on α˜ by a few orders of magnitude. Furthermore, we observe that the constraint is insensitive to the mass of the stellar system and the dark matter density in the stellar system as long as the system is dark matter dominated. This new approach can be applied to many other stellar systems, and we obtain comparable constraints from compact stellar halos observed in ultrafaint dwarf galaxies. Published by the American Physical Society 2025

Spatial distribution and clustering properties of the young stellar populations in the Carina Nebula complex and Car OB1

Aims. We use Gaia DR3 astrometry and photometry to analyze the spatial distribution of the young stellar populations and stellar clusters and to search for new OB star candidates in the Carina Nebula complex and the full extent (∼5°, corresponding to ∼200 pc) of the Car OB1 association. Methods. We first performed a new census of high-mass stars in Car OB1 and compiled a comprehensive catalog of 517 stars with known spectral types (128 O-type, WR, and supergiant stars, and 389 B-type stars) that have Gaia DR3 parallaxes consistent with membership in the association. We applied the clustering algorithm DBSCAN on the Gaia DR3 data of the region to find stellar clusters, determine their distances and kinematics, and estimate ages. We also used Gaia astrometry and the additional astrophysical_parameters table to perform a spatially unbiased search for further high-mass members of Car OB1 over the full area of the association. Results. Our DBSCAN analysis finds 15 stellar clusters and groups in Car OB1, four of which were not known before. Most clusters (80%) show signs of expansion or contraction, four of them with a ≥2σ significance. We find a global expansion of the Car OB1 association with a velocity of vout = 5.25 ± 0.02 km s−1. A kinematic traceback of the high-mass stars shows that the spatial extent of the association was at a minimum 3–4 Myr ago. Using astrophysical parameters by Gaia DR3, we identified 15 new O-type and 589 new B-type star candidates in Car OB1. The majority (≳54%) of the high-mass stars constitute a non-clustered distributed stellar population. Based on our sample of high-mass stars, we estimate a total stellar population of at least ∼8 × 104 stars in Car OB1. Conclusions. Our study is the first systematic astrometric analysis that covers the full spatial extent of the Car OB1 association, and it therefore substantially increases the knowledge of the distributed stellar population and spatial evolution of the entire association. Our results suggest suggests Car OB1 to be the most massive known star-forming complex in our Galaxy.

Mapping the Milky Way with Gaia Bp/Rp spectra

Context. Gaia Bp/Rp spectrophotometry for over two hundred million stars has been publicly released as part of Gaia Data Release 3 (DR3). These data have great potential for mapping metallicity across the Milky Way. Several recent studies have analyzed this data set to derive atmospheric parameters and identify new metal-poor stars. In addition, systematics in the fluxes of the Bp/Rp spectra have also been identified and characterized. Aims. We aim to construct an alternative catalog of atmospheric parameters from Gaia Bp/Rp spectra by fitting them with synthetic spectra based on model atmospheres, and provide corrections to the Bp/Rp fluxes according to stellar colors, magnitudes, and interstellar extinction. Methods. We use GaiaXPy to obtain calibrated spectra and apply FERЯ to match the corrected Bp/Rp spectra with models and infer atmospheric parameters. We train a neural network (NN) using stars in the Apache Point Observatory Galactic Evolution Experiment (APOGEE) to predict flux corrections as a function of wavelength for each target. Results. Based on the comparison with APOGEE parameters, we conclude that our estimated parameters have systematic errors and uncertainties in Teff, log g, and [M/H] about −38 ± 167 K, 0.05 ± 0.40 dex, and −0.12 ± 0.19 dex, respectively, for stars in the range 4000 ≤ Teff ≤ 7000 K. The corrected Bp/Rp spectra show improved agreement with both models and Hubble Space Telescope (HST) CALSPEC data. Our correction increases the precision of the relative spectrophotometry of the Bp/Rp data from 3.2–3.7% to 1.2–2.4%. We also compare our results with other similar catalogs from the literature and validate them using star clusters. Finally, we have built a catalog of atmospheric parameters for stars within 4000 ≤ Teff ≤ 7000 K, comprising 68 394 431 sources, along with a subset of 124 188 stars with [M/H] ≤ −2.5. Our catalogs and flux correction code are publicly available. Conclusions. Our results confirm that the Gaia Bp/Rp flux calibrated spectra show systematic patterns as a function of wavelength that are tightly related to colors, magnitudes, and extinction. Our optimization algorithm can give us accurate atmospheric parameters of stars with a clear and direct link to models of stellar atmospheres, and can be used to efficiently search for extremely metal-poor (EMP) stars.

The VISCACHA Survey

Context. In the Large Magellanic Cloud (LMC), only seven star clusters have been discovered to be older than ∼4 Gyr and younger than ∼10 Gyr, placing them in what is known as the age gap. Aims. We aim to analyze the photometric data from the VISCACHA survey in the V and I bands to determine, for the first time, the astrophysical parameters of SL 2, revealing that the cluster is indeed situated within the age gap. Methods. We used our newly developed SIESTA code to carry out a statistical isochrone fitting with synthetic color-magnitude diagrams (CMDs) to determine the cluster age, metallicity, distance, color excess, and binary fraction with two grids of stellar evolution models. In addition, the cluster mass was estimated based on its integrated magnitude. Results. The ages obtained from isochrone fitting are compatible with the age gap, amounting to (7.17 ± 0.35) Gyr when using PARSEC-COLIBRI isochrones and (8.02 ± 0.45) Gyr when using MIST. Notably, SL 2 is the first age gap cluster discovered in the southern region of the LMC. The mass of the cluster is considerably smaller than that of the group of older LMC clusters. Conclusions. SL 2 has a comparable metallicity to the other two age gap clusters with similar ages, namely, ESO 121-03 and KMHK 1592, as well as the LMC field star population. While the discovery of a new cluster with such characteristics could be seen as evidence that age gap clusters were formed in situ, the heliocentric distance of SL2 locates it far from the LMC center, akin to the SMC distance. Therefore, the question of its origin, alongside that of other age gap clusters, remains unresolved and open to further investigation.

The S2 orbit and tidally disrupted binaries: Indications for collisional depletion in the Galactic center

The properties of the stellar cluster surrounding Sagittarius A* can be assessed indirectly through the motion of the S-stars. Specifically, the current accuracy to which the prograde precession of the S2 star is measured allows one to place significant constraints on the extended mass enclosed by its orbit. We suggest that high velocity destructive collisions (DCs) offer a natural mechanism for depleting the mass inside the S2 orbit, thus allowing the measured precession and the existence of a dense stellar cluster to be reconciled. Such a solution is especially necessary when considering that stars are supplied to the inner part of the cluster by both dynamical relaxation and by being captured in tight orbits during tidal disruption of binaries. We use analytic arguments and results from simulations to demonstrate that in order to obtain a precession that is consistent with observations, collisional depletion is necessary if the capture rate is greater than a few 10−6 yr−1. We also show that fluctuations arising from the finite number of stars cannot serve as an alternative to DCs for generating consistency with the observed S2 precession. We conclude that astrometric observations of the S-stars provide a meaningful indication that the inner part of the Galactic center is shaped by collisional depletion, supporting the hypothesis that DCs occur in galactic nuclei at an astrophysically significant rate.

Give to Ursa Minor what is Ursa Minor’s: An updated census of the RR Lyrae population in the Ursa Minor dwarf galaxy based on Gaia DR3

Aims. We used RR Lyrae stars identified by the Gaia third data release (DR3) to explore the outskirts of the Ursa Minor (UMi) dwarf spheroidal galaxy (dSph) and update the census of its variable star population. Methods. We adopted different tools based on the Gaia DR3 astrometric and photometric data (proper motions, Period–Wesenheit–Metallicity relations, spatial distribution, colour–magnitude diagram and stellar isochrone fitting) to discriminate between different types of variable stars, and to identify UMi members. Results. We found a total of 129 RR Lyrae stars and 10 Anomalous Cepheids (ACs) that belong to UMi. In this paper we report 47 new RR Lyrae stars (46 bona fide and 1 candidate) and 5 new ACs (4 bona fide and 1 candidate), including new possible members in the extreme periphery of the galaxy at a distance of ∼12 half-light radii. We reclassified 13 RR Lyrae stars identified by the Gaia DR3 Specific Object Study pipeline for Cepheids and RR Lyrae stars (SOS Cep&RRL), using data from the literature and Gaia astrometry and photometry. Specifically, we assigned these 13 DR3 RR Lyrae stars to ten Anomalous Cepheids and three doublemode RR Lyrae (RRd), respectively. From the average luminosity of the RR Lyrae stars we derive for UMi a distance modulus of (m − M)0 = 19.23 ± 0.11 mag, in excellent agreement with the literature. Finally, we investigated whether some of UMi’s variable stars might be members of the ultra-faint stellar cluster Muñoz 1 that lies at a projected distance of 45′ from UMi’s centre. Based on the properties of the variable stars (distances, colours, and metallicities), we find it unlikely that they belong to the cluster.

Asteroseismic Study of Subgiants and Giants of the Open Cluster M67 using Kepler/K2: Expanded Sample and Precise Masses

Abstract Sparked by the asteroseismic space revolution, ensemble studies have been used to produce empirical relations linking observed seismic properties and fundamental stellar properties. Cluster stars are particularly valuable because they have the same metallicity, distance, and age, thus reducing scatter to reveal smoother relations. We present the first study of a cluster that spans the full evolutionary sequence from subgiants to core helium-burning red giants using asteroseismology to characterise the stars in M67, including a yellow straggler. We use Kepler/K2 data to measure seismic surface gravity, examine the potential influence of core magnetic fields, derive an empirical expression for the seismic surface term, and determine the phase term ε of the asymptotic relation for acoustic modes, extending its analysis to evolutionary states previously unexplored in detail. Additionally, we calibrate seismic scaling relations for stellar mass and radius, and quantify their systematic errors if surface term corrections are not applied to state-of-the-art stellar models. Our masses show that the Reimers mass loss parameter can not be larger than η ∼ 0.23 at the 2σ level. We use isochrone models designed for M67 and compare their predictions with individual mode frequencies. We find that the seismic masses for subgiants and red giant branch stars align with the isochrone-predicted masses as per their luminosity and colour. However, our results are inconsistent with the mass of one of the stellar components of an eclipsing binary system near the TAMS. We use traditional seismic χ2 fits to estimate a seismic cluster age of 3.95 ± 0.35 Gyrs.

Formation of free-floating planetary mass objects via circumstellar disk encounters.

The origin of planetary mass objects (PMOs) wandering in young star clusters remains enigmatic, especially when they come in pairs. They could represent the lowest-mass object formed via molecular cloud collapse or high-mass planets ejected from their host stars. However, neither theory fully accounts for their abundance and multiplicity. Here, we show via hydrodynamic simulations that free-floating PMOs have a unique formation channel via the fragmentation of tidal bridges between encountering circumstellar disks. This process can be highly productive in dense clusters like Trapezium forming metal-poor PMOs with disks. Free-floating multiple PMOs also naturally emerge when neighboring PMOs are caught by their mutual gravity. PMOs may thus form a distinct population that is fundamentally different from stars and planets.

Using Detailed Single-star and Binary-evolution Models to Probe the Large Observed Luminosity Spread of Red Supergiants in Young Open Star Clusters

Abstract Red supergiants (RSGs) represent a late evolutionary stage of massive stars. Recent observations reveal that the observed luminosity range of RSGs in young open clusters is wider than expected from single-star evolution models. Binary evolution effects have been suggested as a possible explanation. Here, we analyze 3670 detailed binary-evolution models, as well as corresponding single-star models, to probe the contribution of binary mass transfer and binary mergers to the luminosity distribution of RSGs in star clusters with ages up to 100 Myr. We confirm that the expected luminosity range of RSGs in a coeval population can span a factor of 10, as a consequence of mergers between two main-sequence stars, which reproduces the observed RSG luminosity ranges in rich clusters well. While the luminosity increase as consequence of mass transfer is more limited, it may help to increase the number of overluminous RSGs. However, our results also demonstrate that binary effects alone are insufficient to account for the number of RSGs found with luminosities of up to 3 times those predicted by current single-star models. We discuss observational accuracy, rotational mixing, age spread, and intrinsic RSG variability as possible explanations. Further observations of RSGs in young open clusters, in particular studies of their intrinsic brightness variability, appear crucial for disentangling these effects.

Investigating Pulsating Variables and Eclipsing Binaries in NGC 2126 using Ground and Space-based Photometry, Astrometry, Spectroscopy and Modeling

Abstract Pulsating variables are prevalent in the classical δ Scuti instability strip of intermediate-age open star clusters. The cluster membership of these stars facilitates a comparative analysis of their evolution in analogous environments. In this study, we integrate ground-based observations, TESS Full Frame Images (FFIs), and Gaia DR3 data to investigate variable stars in the intermediate-age open star cluster NGC 2126. We performed ground-based time-series observations of NGC 2126 to identify variable stars within its vicinity. Next, we determined the membership of these stars using parallax and the proper motions from Gaia DR3 archive. Then, we searched the TESS Full Frame Images (FFIs) for counterparts to the variables identified above and performed their frequency analysis and classification. Finally, we modeled the light curves (LCs) of detected eclipsing binaries (EBs), including V551 Aur, which has a pulsating component. We found 25 members and 85 field variable stars. In TESS FFIs, we found LCs for 11 known variables and a new rotational variable. We determined that the pulsating EB V551 Aur is a member of the cluster. The low- and medium-resolution spectra revealed the line profile variation and the basic parameters for the star, respectively. Simultaneous modeling of the eclipses and the embedded pulsations resulted in improved orbital parameters for the binary system. We also report the determination of orbital parameters for the previously uncharacterized EB system UCAC4 700-043174.

The formation, evolution and disruption of star clusters with improved gravitational dynamics in simulated dwarf galaxies

Abstract So far, even the highest resolution galaxy formation simulations with gravitational softening have failed to reproduce realistic life cycles of star clusters. We present the first star-by-star galaxy models of star cluster formation to account for hydrodynamics, star formation, stellar evolution and collisional gravitational interactions between stars and compact remnants using the updated sphgal+ketju code, part of the griffin-project. Gravitational dynamics in the vicinity of >3 M⊙ stars and their remnants are solved with a regularised integrator (ketju) without gravitational softening. Comparisons of idealised star cluster evolution with sphgal+ketju and direct N-body show broad agreement and the failure of simulations that use gravitational softening. In the hydrodynamical simulations of idealised dwarf galaxies run with sphgal+ketju, clusters up to ∼900 M⊙ form compact (effective radii 0.1–1 pc) and their sizes increase by up to a factor of ten in agreement with previous N-body simulations and the observed sizes of exposed star clusters. The sizes increase rapidly once the clusters become exposed due to photoionising radiation. On average 63 % of the gravitationally bound clusters disrupt during the first 100 Myr of evolution in the galactic tidal field. The addition of collisional dynamics reduces the fraction of supernovae in bound clusters by a factor of ∼1.7, however the global star formation and outflow histories change by less than 30 %. We demonstrate that the accurate treatment of gravitational encounters with massive stars enables more realistic star cluster life cycles from the earliest stages of cluster formation until disruption in simulated low-mass galaxies.

A Comprehensive Catalog of Emission-line Nebulae, Star Clusters, and Supergiants in M31 from the LAMOST Spectroscopic Survey

A Comprehensive Catalog of Emission-line Nebulae, Star Clusters, and Supergiants in M31 from the LAMOST Spectroscopic Survey

Formation of massive star clusters with and without iron abundance spreads in a dwarf galaxy merger

Abstract To study the formation of star clusters and their properties in a dwarf–dwarf merging galaxy, we have performed a numerical simulation of a dwarf–dwarf galaxy merger by using the Tree+GRAPE $N$-body/SPH code ASURA. In our simulation, 13 young star clusters are formed during the merger process. We show that our simulated star clusters can be divided into two types: with and without [Fe$/$H] abundance variations. The former is created by a seed star cluster (the first-generation stars) formed in compressed gas. These stars contaminate the surrounding gas by Type II supernovae. At that time, the energy injection is insufficient to induce an outflow of the surrounding gas. After that, the contaminated gas falls into the seed, thereby forming a new generation of stars from the contaminated gas. We also show that most star clusters are formed in the galactic central region after the second encounter and fall into the galactic center due to dynamical friction within several hundred Myr. As a result, close encounters and mergers between the clusters take place. Although the clusters with shallower gravitational potential are tidally disrupted by these close encounters, others survive and finally merge at the center of the merged dwarf galaxies to create a nuclear star cluster. Therefore, the nuclear star cluster comprises various stellar components in ${[\rm Fe/H]}$ abundance and age. We discuss our work in the context of observations and demonstrate the diagnostic power of high-resolution simulations in the context of star cluster formation.