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The metallicity distributions of globular cluster (GC) systems in galaxies are a critical test of any GC formation scenario. In this work, we investigate the predicted GC metallicity distributions of galaxies in the MOdelling Star cluster population Assembly In Cosmological Simulations within EAGLE (E-MOSAICS) simulation of a representative cosmological volume ($L = 34.4$ comoving Mpc). We find that the predicted GC metallicity distributions and median metallicities from the fiducial E-MOSAICS GC formation model agree well the observed distributions, except for galaxies with masses $M_\ast \sim 2 \times 10^{10}$ M$_\odot$, which contain an overabundance of metal-rich GCs. The predicted fraction of galaxies with bimodal GC metallicity distributions ($37 \pm 2$ per cent in total; $45 \pm 7$ per cent for $M_\ast > 10^{10.5}$ M$_\odot$) is in good agreement with observed fractions ($44^{+10}_{-9}$ per cent), as are the mean metallicities of the metal-poor and metal-rich peaks. We show that, for massive galaxies ($M_\ast > 10^{10}$ M$_\odot$), bimodal GC distributions primarily occur as a result of cluster disruption from initially-unimodal distributions, rather than as a result of cluster formation processes. Based on the distribution of field stars with GC-like abundances in the Milky Way, we suggest that the bimodal GC metallicity distribution of Milky Way GCs also occurred as a result of cluster disruption, rather than formation processes. We conclude that separate formation processes are not required to explain metal-poor and metal-rich GCs, and that GCs can be considered as the surviving analogues of young massive star clusters that are readily observed to form in the local Universe today., 19 pages, 16 figures. Published in MNRAS

We study the morphologies of 3,964 galaxies and their progenitors with $M_\star > 10^{10} M_\odot$ in the reference EAGLE hydrodynamical simulation from redshifts $z=1$ to $z=0$, concentrating on the redshift evolution of the bar fraction. We apply two convolutional neural networks (CNNs) to classify 35,082 synthetic g-band images across 10 snapshots in redshift. We identify galaxies as either barred or unbarred, while also classifying each sample into one of four morphological types: elliptical (E), lenticular (S0), spiral (Sp), and irregular/miscellaneous (IrrM). We find that the bar fraction is roughly constant between $z = 0.0$ to $z = 0.5$ (32% to 33%), before exhibiting a general decline to 26% out to $z = 1$. The bar fraction is highest in spiral galaxies, from 49% at $z = 0$ to 39% at $z = 1$. The bar fraction in S0s is lower, ranging from 22% to 18%, with similar values for the miscellaneous category. Under 5% of ellipticals were classified as barred. We find that the bar fraction is highest in low mass galaxies ($M_\star \leq 10^{10.5} M_\odot$). Through tracking the evolution of galaxies across each snapshot, we find that some barred galaxies undergo episodes of bar creation, destruction and regeneration, with a mean bar lifetime of 2.24 Gyr. We further find that incidences of bar destruction are more commonly linked to major merging, while minor merging and accretion is linked to both bar creation and destruction., 15 pages, 18 figures, accepted for publication in MNRAS

We analyse the surface brightness profiles of disc-type galaxies in the EAGLE simulations in order to investigate the effects of galaxy mass and environment on galaxy profile types. Following observational works, we classify the simulated galaxies by their disc surface brightness profiles into single exponential (Type I), truncated (Type II) and anti-truncated (Type III) profiles. In agreement with previous observation and theoretical work, we find that Type II discs result from truncated star-forming discs that drive radial gradients in the stellar populations. In contrast, Type III profiles result from galaxy mergers, extended star-forming discs or the late formation of a steeper, inner disc. We find that the EAGLE simulations qualitatively reproduce the observed trends found between profile type frequency and galaxy mass, morphology and environment, such as the fraction of Type III galaxies increasing with galaxy mass, and the the fraction of Type II galaxies increasing with Hubble type. We investigate the lower incidence of Type II galaxies in galaxy clusters, finding, in a striking similarity to observed galaxies, that almost no S0-like galaxies in clusters have Type II profiles. Similarly, the fraction of Type II profiles for disc-dominated galaxies in clusters is significantly decreased relative to field galaxies. This difference between field and cluster galaxies is driven by star formation quenching. Following the cessation of star formation upon entering a galaxy cluster, the young stellar populations of Type II galaxies simply fade, leaving behind Type I galaxies., 11 pages, 10 figures. Accepted for publication in MNRAS

It has long been argued that the radial distribution of globular clusters (GCs) in the Fornax dwarf galaxy requires its dark matter halo to have a core of size $\sim 1$ kpc. We revisit this argument by investigating analogues of Fornax formed in E-MOSAICS, a cosmological hydrodynamical simulation that self-consistently follows the formation and evolution of GCs in the EAGLE galaxy formation model. In EAGLE, Fornax-mass haloes are cuspy and well described by the Navarro-Frenk-White profile. We post-process the E-MOSAICS to account for GC orbital decay by dynamical friction, which is not included in the original model. Dynamical friction causes 33 per cent of GCs with masses $M_{\rm GC}\geq4\times10^4 {~\rm M_\odot}$ to sink to the centre of their host where they are tidally disrupted. Fornax has a total of five GCs, an exceptionally large number compared to other galaxies of similar stellar mass. In the simulations, we find that only 3 per cent of the Fornax analogues have five or more GCs, while 30 per cent have only one and 35 per cent have none. We find that GC systems in satellites are more centrally concentrated than in field dwarfs, and that those formed in situ (45 per cent) are more concentrated than those that were accreted. The survival probability of a GC increases rapidly with the radial distance at which it formed ($r_{\rm init}$): it is 37 per cent for GCs with $r_{\rm init} \leq 1$ kpc and 92 per cent for GCs with $r_{\rm init} \geq 1$ kpc. The present-day radial distribution of GCs in E-MOSAICS turns out to be indistinguishable from that in Fornax, demonstrating that, contrary to claims in the literature, the presence of five GCs in the central kiloparsec of Fornax does not exclude a cuspy DM halo., 15 pages, 13 figures. submitted to MNRAS, comments welcome!

We use the hydrodynamical EAGLE simulation to test if ultra-compact dwarf galaxies (UCDs) can form by tidal stripping by predicting the ages and metallicities of tidally stripped galaxy nuclei in massive galaxy clusters, and compare these results to compiled observations of age and metallicities of observed UCDs. We further calculate the colours of our sample of simulated stripped nuclei using SSP models and compare these colours to observations of UCDs in the Virgo cluster. We find that the ages of observed UCDs are consistent with simulated stripped nuclei, with both groups of objects having a mean age > 9 Gyr. Both stripped nuclei and UCDs follow a similar mass-metallicity relationship, and the metallicities of observed UCDs are consistent with those of simulated stripped nuclei for objects with M > $10^{7}~M_{\odot}$. The colours of observed UCDs are also consistent with our simulated stripped nuclei, for objects with M > $10^{7}~M_{\odot}$, with more massive objects being redder. We find that the colours of stripped nuclei exhibit a bimodal red and blue distribution that can be explained by the dependency of colour on age and metallicity, and by the mass-colour relation. We additionally find that our low mass stripped nuclei sample is consistent with the colour of blue globular clusters. We conclude that the internal properties of simulated nuclei support the tidal stripping model of UCD formation., 12 pages, 9 figures

Linking globular clusters (GCs) to the assembly of their host galaxies is an overarching goal in GC studies. The inference of tight scaling relations between GC system properties and the mass of both the stellar and dark halo components of their host galaxies are indicative of an intimate physical connection, yet have also raised fundamental questions about how and when GCs form. Specifically, the inferred correlation between the mass of a GC system (Mgc) and the dark matter halo mass (Mhalo) of a galaxy has been posited as a consequence of a causal relation between the formation of dark matter mini-haloes and GC formation during the early epochs of galaxy assembly. We present the first results from a new simulation of a cosmological volume ($L=34.4$~cMpc on a side) from the E-MOSAICS suite, which includes treatments of the formation and evolution of GCs within the framework of a detailed galaxy formation model. The simulated Mgc-Mhalo relation is linear for halo masses $>5\times10^{11}~Msun$, and is driven by the hierarchical assembly of galaxies. Below this halo mass, the simulated relation features a downturn, which we show is consistent with observations, and is driven by the underlying stellar mass-halo mass relation of galaxies. Our fiducial model reproduces the observed Mgc-Mstar relation across the full mass range, which we argue is more physically relevant than the Mgc-Mhalo relation. We also explore the physical processes driving the observed constant value of $Mgc / Mhalo \sim 5\times10^{-5}$ and find that it is the result of a combination of cluster formation physics and cluster disruption., 13 pages, 9 figures, accepted for publication in MNRAS

Modern observational and analytic techniques now enable the direct measurement of star formation histories and the inference of galaxy assembly histories. However, current theoretical predictions of assembly are not ideally suited for direct comparison with such observational data. We therefore extend the work of prior examinations of the contribution of ex-situ stars to the stellar mass budget of simulated galaxies. Our predictions are specifically tailored for direct testing with a new generation of observational techniques by calculating ex-situ fractions as functions of galaxy mass and morphological type, for a range of surface brightnesses. These enable comparison with results from large FoV IFU spectrographs, and increasingly accurate spectral fitting, providing a look-up method for the estimated accreted fraction. We furthermore provide predictions of ex-situ mass fractions as functions of galaxy mass, galactocentric radius and environment. Using $z=0$ snapshots from the 100cMpc$^3$ and 25cMpc$^3$ EAGLE simulations we corroborate the findings of prior studies, finding that ex-situ fraction increases with stellar mass for central and satellite galaxies in a stellar mass range of 2$\times$10$^{7}$ - 1.9$\times$10$^{12}$ M$_{\odot}$. For those galaxies of mass M$_*$>5$\times$10$^{8}$M$_{\odot}$, we find that the total ex-situ mass fraction is greater for more extended galaxies at fixed mass. When categorising satellite galaxies by their parent group/cluster halo mass we find that the ex-situ fraction decreases with increasing parent halo mass at fixed galaxy mass. This apparently counter-intuitive result may be the result of high passing velocities within large cluster halos inhibiting efficient accretion onto individual galaxies., 16 pages, 11 figures. Accepted for publication in MNRAS

Globular clusters (GCs) are typically old, with most having formed at z >~ 2. This makes understanding their birth environments difficult, as they are typically too distant to observe with sufficient angular resolution to resolve GC birth sites. Using 25 cosmological zoom-in simulations of Milky Way-like galaxies from the E-MOSAICS project, with physically-motivated models for star formation, feedback, and the formation, evolution, and disruption of GCs, we identify the birth environments of present-day GCs. We find roughly half of GCs in these galaxies formed in-situ (52.0 +/- 1.0 per cent) between z ~ 2 - 4, in turbulent, high-pressure discs fed by gas that was accreted without ever being strongly heated through a virial shock or feedback. A minority of GCs form during mergers (12.6 +/- 0.6 per cent in major mergers, and 7.2 +/- 0.5 per cent in minor mergers), but we find that mergers are important for preserving the GCs seen today by ejecting them from their natal, high density interstellar medium (ISM), where proto-GCs are rapidly destroyed due to tidal shocks from ISM substructure. This chaotic history of hierarchical galaxy assembly acts to mix the spatial and kinematic distribution of GCs formed through different channels, making it difficult to use observable GC properties to distinguish GCs formed in mergers from ones formed by smooth accretion, and similarly GCs formed in-situ from those formed ex-situ. These results suggest a simple picture of GC formation, in which GCs are a natural outcome of normal star formation in the typical, gas-rich galaxies that are the progenitors of present-day galaxies., 20 pages, 20 figures, resubmitted to MNRAS after accounting for referee's comments

Many disc galaxies in clusters have been found with bulges of similar age or younger than their surrounding discs, at odds with field galaxies of similar morphology and their expected inside-out formation. We use the EAGLE simulations to test potential origins for this difference in field and cluster galaxies. We find, in agreement with observations, that on average disc-dominated field galaxies in the simulations have older inner regions, while similar galaxies in groups and clusters have similarly aged or younger inner regions. This environmental difference is a result of outside-in quenching of the cluster galaxies. Prior to group/cluster infall, galaxies of a given present-day mass and morphology exhibit a similar evolution in their specific star formation rate (sSFR) profiles. Post-infall, the outer sSFRs of group and cluster galaxies significantly decrease due to interstellar medium stripping, while the central sSFR remains similar to field galaxies. Field disc galaxies instead generally retain radially increasing sSFR profiles. Thus, field galaxies continue to develop negative age gradients (younger discs), while cluster galaxies instead develop positive age gradients (younger bulges)., 14 pages, 11 figures. Accepted for publication in MNRAS

The optical morphology of galaxies is strongly related to galactic environment, with the fraction of early-type galaxies increasing with local galaxy density. In this work we present the first analysis of the galaxy morphology-density relation in a cosmological hydrodynamical simulation. We use a convolutional neural network, trained on observed galaxies, to perform visual morphological classification of galaxies with stellar masses $M_\ast > 10^{10} \, \mathrm{M}_\odot$ in the EAGLE simulation into elliptical, lenticular and late-type (spiral/irregular) classes. We find that EAGLE reproduces both the galaxy morphology-density and morphology-mass relations. Using the simulations, we find three key processes that result in the observed morphology-density relation: (i) transformation of disc-dominated galaxies from late-type (spiral) to lenticular galaxies through gas stripping in high-density environments, (ii) formation of lenticular galaxies by merger-induced black hole feedback in low-density environments, and (iii) an increasing fraction of high-mass galaxies, which are more often elliptical galaxies, at higher galactic densities., 19 pages, 17 figures, published in MNRAS

We study the present-day rotational velocity ($V_{rot}$) and velocity dispersion (${\sigma}$) profiles of the globular cluster (GC) systems in a sample of 50 lenticular (S0) galaxies from the E-MOSAICS galaxy formation simulations. We find that 82% of the galaxies have GCs that are rotating along the photometric major axis of the galaxy ($aligned$), while the remaining 18% of the galaxies do not ($misaligned$). This is generally consistent with the observations from the SLUGGS survey. For the $aligned$ galaxies, classified as $peaked$ $and$ $outwardly$ $decreasing$ (49%), $flat$ (24%) and $increasing$ (27%) based on the $V_{rot}/{\sigma}$ profiles out to large radii, we do not find any clear correlation between these present-day $V_{rot}/{\sigma}$ profiles of the GCs and the past merger histories of the S0 galaxies, unlike in previous simulations of galaxy stars. For just over half of the $misaligned$ galaxies, we find that the GC misalignment is the result of a major merger within the last 10 Gyr so that the $ex$-$situ$ GCs are misaligned by an angle between 0{\deg} (co-rotation) to 180{\deg} (counter-rotation) with respect to the $in$-$situ$ GCs, depending on the orbital configuration of the merging galaxies. For the remaining $misaligned$ galaxies, we suggest that the $in$-$situ$ metal-poor GCs, formed at early times, have undergone more frequent kinematic perturbations than the $in$-$situ$ metal-rich GCs. We also find that the GCs accreted early and the $in$-$situ$ GCs are predominantly located within 0.2 virial radii ($R_{200}$) from the centre of galaxies in 3D phase-space diagrams., Comment: 19 pages, 13 figures

The α-element abundances of the globular cluster (GC) and field star populations of galaxies encode information about the formation of each of these components. We use the E-MOSAICS cosmological simulations of ∼L* galaxies and their GCs to investigate the [α/Fe]–[Fe/H] distribution of field stars and GCs in 25 Milky Way–mass galaxies. The [α/Fe]–[Fe/H] distribution of GCs largely follows that of the field stars and can also therefore be used as tracers of the [α/Fe]–[Fe/H] evolution of the galaxy. Due to the difference in their star formation histories, GCs associated with stellar streams (i.e. which have recently been accreted) have systematically lower [α/Fe] at fixed [Fe/H]. Therefore, if a GC is observed to have low [α/Fe] for its [Fe/H] there is an increased possibility that this GC was accreted recently alongside a dwarf galaxy. There is a wide range of shapes for the field star [α/Fe]–[Fe/H] distribution, with a notable subset of galaxies exhibiting bimodal distributions, in which the high [α/Fe] sequence is mostly comprised of stars in the bulge, a high fraction of which are from disrupted GCs. We calculate the contribution of disrupted GCs to the bulge component of the 25 simulated galaxies and find values between 0.3 and 14 per cent, where this fraction correlates with the galaxy’s formation time. The upper range of these fractions is compatible with observationally inferred measurements for the Milky Way, suggesting that in this respect the Milky Way is not typical of L*galaxies, having experienced a phase of unusually rapid growth at early times.

We present an analysis of young star clusters (YSCs) that form in the E-MOSAICS cosmological, hydrodynamical simulations of galaxies and their star cluster populations. Through comparisons with observed YSC populations, this work aims to test models for YSC formation and obtain an insight into the formation processes at work in part of the local galaxy population. We find that the models used in E-MOSAICS for the cluster formation efficiency and high-mass truncation of the initial cluster mass function ($M_\mathrm{c,\ast}$) both quantitatively reproduce the observed values of cluster populations in nearby galaxies. At higher redshifts ($z \geq 2$, near the peak of globular cluster formation) we find that, at a constant star formation rate (SFR) surface density, $M_\mathrm{c,\ast}$ is larger than at $z=0$ by a factor of four due to the higher gas fractions in the simulated high-redshift galaxies. Similar processes should be at work in local galaxies, offering a new way to test the models. We find that cluster age distributions may be sensitive to variations in the cluster formation rate (but not SFR) with time, which may significantly affect their use in tests of cluster mass loss. By comparing simulations with different implementations of cluster formation physics, we find that (even partially) environmentally-independent cluster formation is inconsistent with the brightest cluster-SFR and specific luminosity-$\Sigma_\mathrm{SFR}$ relations, whereas these observables are reproduced by the fiducial, environmentally-varying model. This shows that models in which a constant fraction of stars form in clusters are inconsistent with observations., Comment: 20 pages, 17 figures, accepted for publication in MNRAS

We present the evolution of the rest-frame ultraviolet (UV) properties of the globular cluster (GC) populations and their host galaxies formed in the E-MOSAICS suite of cosmological hydrodynamical simulations. We compute the luminosities of all clusters associated with 25 simulated Milky Way-mass galaxies, discussed in previous works, in the rest-frame UV and optical bands by combining instantaneous cluster properties (age, mass, metallicity) with simple stellar population models, from redshifts $z=0$ to 10. Due to the rapid fading of young stellar populations in the UV, most of the simulated galaxies do not host GCs bright enough to be individually identified in deep Hubble Space Telescope (HST) observations, even in highly magnified systems. The median age of the most UV-luminous GCs is $2$ is typically $M_{\rm UV} \sim -16$, consistent with the luminosities of observed compact, high-redshift sources., 15 pages, 9 figures, accepted for publication in MNRAS (4 June 2019)

A number of the massive clusters in the halo, bulge and disc of the Galaxy are not genuine globular clusters (GCs), but instead are different beasts altogether. They are the remnant nuclear star clusters (NSCs) of ancient galaxies since accreted by the Milky Way. While some clusters are readily identifiable as NSCs, and can be readily traced back to their host galaxy (e.g., M54 and the Sagittarius Dwarf galaxy) others have proven more elusive. Here we combine a number of independent constraints, focusing on their internal abundances and overall kinematics, to find NSCs accreted by the Galaxy and trace them to their accretion event. We find that the true NSCs accreted by the Galaxy are: M54 from the Sagittarius Dwarf, $\omega$ Centari from Gaia-Enceladus/Sausage, NGC 6273 from Kraken and (potentially) NGC 6934 from the Helmi Streams. These NSCs are prime candidates for searches of intermediate mass black holes (BHs) within star clusters, given the common occurrence of galaxies hosting both NSCs and central massive BHs. No NSC appears to be associated with Sequoia or other minor accretion events. Other claimed NSCs are shown not to be such. We also discuss the peculiar case of Terzan 5, which may represent a unique case of a cluster-cluster merger., Comment: 11 pages, accepted for publication in MNRAS

We use the hydrodynamical EAGLE simulation to predict the numbers, masses and radial distributions of tidally stripped galaxy nuclei in massive galaxy clusters, and compare these results to observations of ultra-compact dwarf galaxies (UCDs) in the Virgo cluster. We trace the merger trees of galaxies in massive galaxy clusters back in time and determine the numbers and masses of stripped nuclei from galaxies disrupted in mergers. The spatial distribution of stripped nuclei in the simulations is consistent with those of UCDs surrounding massive galaxies in the Virgo cluster. Additionally, the numbers of stripped nuclei are consistent with the numbers of M > $10^{7}~M_{\odot}$ UCDs around individual galaxies and in the Virgo cluster as a whole. The mass distributions in this mass range are also consistent. We find that the numbers of stripped nuclei surrounding individual galaxies correlates better with the stellar or halo mass of individual galaxies than the total cluster mass. We conclude that most high mass (M > $10^{7}~M_{\odot}$ UCDs are likely stripped nuclei. It is difficult to draw reliable conclusions about low mass (M < $10^{7}~M_{\odot}$ UCDs because of observational selection effects. We additionally predict that a few hundred stripped nuclei below a mass of $2~\times~10^{6}~M_{\odot}$ should exist in massive galaxies that will overlap in mass with the globular cluster population. Approximately 1-3 stripped nuclei in the process of forming also exist per massive galaxy., 17 pages, 16 figures, Published in MNRAS

We set out to compare the age-metallicity relation (AMR) of massive clusters from Magellanic Cloud mass galaxies in the E-MOSAICS suite of numerical cosmological simulations with an amalgamation of observational data of massive clusters in the Large and Small Magellanic Clouds (LMC/SMC). We aim to test if: i) star cluster formation proceeds according to universal physical processes, suggestive of a common formation mechanism for young-massive clusters (YMCs), intermediate-age clusters (IACs), and ancient globular clusters (GCs); ii) massive clusters of all ages trace a continuous AMR; iii) the AMRs of smaller mass galaxies show a shallower relation when compared to more massive galaxies. Our results show that, within the uncertainties, the predicted AMRs of L/SMC-mass galaxies with similar star formation histories to the L/SMC follow the same relation as observations. We also find that the metallicity at which the AMR saturates increases with galaxy mass, which is also found for the field star AMRs. This suggests that relatively low-metallicity clusters can still form in dwarfs galaxies. Given our results, we suggest that ancient GCs share their formation mechanism with IACs and YMCs, in which GCs are the result of a universal process of star cluster formation during the early episodes of star formation in their host galaxies., Accepted for publication in MNRAS

We report evidence from APOGEE for the presence of a new metal-poor stellar structure located within $\sim$4~kpc of the Galactic centre. Characterised by a chemical composition resembling those of low mass satellites of the Milky Way, this new inner Galaxy structure (IGS) seems to be chemically and dynamically detached from more metal-rich populations in the inner Galaxy. We conjecture that this structure is associated with an accretion event that likely occurred in the early life of the Milky Way. Comparing the mean elemental abundances of this structure with predictions from cosmological numerical simulations, we estimate that the progenitor system had a stellar mass of $\sim5\times10^8M_\odot$, or approximately twice the mass of the recently discovered Gaia-Enceladus/Sausage system. We find that the accreted:{\it in situ} ratio within our metal-poor ([Fe/H]$, Comment: Accepted for publication in MNRAS. 22 pages, 13 Figures

We use the age-metallicity distribution of 96 Galactic globular clusters (GCs) to infer the formation and assembly history of the Milky Way (MW), culminating in the reconstruction of its merger tree. Based on a quantitative comparison of the Galactic GC population to the 25 cosmological zoom-in simulations of MW-mass galaxies in the E-MOSAICS project, which self-consistently model the formation and evolution of GC populations in a cosmological context, we find that the MW assembled quickly for its mass, reaching $\{25,50\}\%$ of its present-day halo mass already at $z=\{3,1.5\}$ and half of its present-day stellar mass at $z=1.2$. We reconstruct the MW's merger tree from its GC age-metallicity distribution, inferring the number of mergers as a function of mass ratio and redshift. These statistics place the MW's assembly $\textit{rate}$ among the 72th-94th percentile of the E-MOSAICS galaxies, whereas its $\textit{integrated}$ properties (e.g. number of mergers, halo concentration) match the median of the simulations. We conclude that the MW has experienced no major mergers (mass ratios $>$1:4) since $z\sim4$, sharpening previous limits of $z\sim2$. We identify three massive satellite progenitors and constrain their mass growth and enrichment histories. Two are proposed to correspond to Sagittarius (few $10^8~{\rm M}_\odot$) and the GCs formerly associated with Canis Major ($\sim10^9~{\rm M}_\odot$). The third satellite has no known associated relic and was likely accreted between $z=0.6$-$1.3$. We name this enigmatic galaxy $\textit{Kraken}$ and propose that it is the most massive satellite ($M_*\sim2\times10^9~{\rm M}_\odot$) ever accreted by the MW. We predict that $\sim40\%$ of the Galactic GCs formed ex-situ (in galaxies with masses $M_*=2\times10^7$-$2\times10^9~{\rm M}_\odot$), with $6\pm1$ being former nuclear clusters., Comment: 24 pages (including appendices), 6 figures, 5 tables; accepted by MNRAS (June 12, 2018), originally submitted on March 25, 2018; Figures 4 and 6 show the main results of the paper. Updated with published version, clarifying the intended historical use of "Canis Major" as referring to a group of GCs rather than a galaxy

We introduce the MOdelling Star cluster population Assembly In Cosmological Simulations within EAGLE (E-MOSAICS) project. E-MOSAICS incorporates models describing the formation, evolution and disruption of star clusters into the EAGLE galaxy formation simulations, enabling the examination of the co-evolution of star clusters and their host galaxies in a fully cosmological context. A fraction of the star formation rate of dense gas is assumed to yield a cluster population; this fraction, and the population's initial properties, are governed by the physical properties of the natal gas. The subsequent evolution and disruption of the entire cluster population is followed accounting for two-body relaxation, stellar evolution, and gravitational shocks induced by the local tidal field. This introductory paper presents a detailed description of the model and initial results from a suite of 10 simulations of $\sim L^\star$ galaxies with disc-like morphologies at $z=0$. The simulations broadly reproduce key observed characteristics of young star clusters and globular clusters (GCs), without invoking separate formation mechanisms for each population. The simulated GCs are the surviving population of massive clusters formed at early epochs ($z\gtrsim1-2$), when the characteristic pressures and surface densities of star-forming gas were significantly higher than observed in local galaxies. We examine the influence of the star formation and assembly histories of galaxies on their cluster populations, finding that (at similar present-day mass) earlier-forming galaxies foster a more massive and disruption-resilient cluster population, while galaxies with late mergers are capable of forming massive clusters even at late cosmic epochs. (Abridged), 40 pages, 29 figures, accepted for publication in MNRAS (30 November 2017)

The ages and metallicities of globular clusters (GCs) are known to be powerful tracers of the properties of their progenitor galaxies, enabling their use in determining the merger histories of galaxies. However, while useful in separating GCs into individual accretion events, the orbits of GC groups themselves have received less attention as probes of their progenitor galaxy properties. In this work, we use simulations of galaxies and their GC systems from the E-MOSAICS project to explore how the present-day orbital properties of GCs are related to the properties of their progenitor galaxies. We find that the orbits of GCs deposited by accretion events are sensitive to the mass and merger redshift of the satellite galaxy. Earlier mergers and larger galaxy masses deposit GCs at smaller median apocentres and lower total orbital energy. The orbital properties of accreted groups of GCs can therefore be used to infer the properties of their progenitor galaxy, though there exists a degeneracy between galaxy mass and accretion time. Combining GC orbits with other tracers (GC ages, metallicities) will help to break the galaxy mass/accretion time degeneracy, enabling stronger constraints on the properties of their progenitor galaxy. In situ GCs generally orbit at lower energies (small apocentres) than accreted GCs, however they exhibit a large tail to high energies and even retrograde orbits (relative to the present-day disc), showing significant overlap with accreted GCs. Applying the results to Milky Way GCs groups suggests a merger redshift $z \sim 1.5$ for the Gaia Sausage/Enceladus and $z>2$ for the `low-energy'/Kraken group, adding further evidence that the Milky Way had two significant mergers in its past., 13 pages, 7 figures. Accepted for publication in MNRAS (21 September 2020)

We summarise recent results from analysis of APOGEE/Gaia data for stellar populations in the Galactic halo, disk, and bulge, leading to constraints on the contribution of dwarf galaxies and globular clusters to the stellar content of the Milky Way halo. Interpretation of the extant data in light of cosmological numerical simulations suggests that the Milky Way has been subject to an unusually intense accretion history at z >~ 1.5., To Appear in "Star Clusters: From the Milky Way to the Early Universe ", Proceedings of IAU Symposium No. 351, 2019, A. Bragaglia, M.B. Davies, A. Sills & E. Vesperini, eds. Four pages, no figures

Globular clusters (GCs) have been posited, alongside dwarf galaxies, as significant contributors to the field stellar population of the Galactic halo. In order to quantify their contribution, we examine the fraction of halo stars formed in stellar clusters in the suite of 25 present-day Milky Way-mass cosmological zoom simulations from the E-MOSAICS project. We find that a median of $2.3$ and $0.3$ per cent of the mass in halo field stars formed in clusters and GCs, defined as clusters more massive than $5\times 10^3$ and $10^5~M_{\odot}$, respectively, with the $25$-$75$th percentiles spanning $1.9$-$3.0$ and $0.2$-$0.5$ per cent being caused by differences in the assembly histories of the host galaxies. Under the extreme assumption that no stellar cluster survives to the present day, the mass fractions increase to a median of $5.9$ and $1.8$ per cent. These small fractions indicate that the disruption of GCs plays a sub-dominant role in the build-up of the stellar halo. We also determine the contributed halo mass fraction that would present signatures of light-element abundance variations considered to be unique to GCs, and find that clusters and GCs would contribute a median of $1.1$ and $0.2$ per cent, respectively. We estimate the contributed fraction of GC stars to the Milky Way halo, based on recent surveys, and find upper limits of $2$-$5$ per cent (significantly lower than previous estimates), suggesting that models other than those invoking strong mass loss are required to describe the formation of chemically enriched stellar populations in GCs., 7 pages, 2 figures; submitted to MNRAS (Oct. 10th 2019)

Globular cluster ages provide both an important test of models of globular cluster formation and a powerful method to constrain the assembly history of galaxies. Unfortunately, measuring the ages of unresolved old stellar populations has proven challenging. Here, we present a novel technique that combines optical photometry with metallicity constraints from near-infrared spectroscopy in order to measure ages. After testing the method on globular clusters in the Milky Way and its satellite galaxies, we apply our technique to three massive early-type galaxies using data from the SLUGGS Survey. The three SLUGGS galaxies and the Milky Way show dramatically different globular cluster age and metallicity distributions, with NGC 1407 and the Milky Way showing mostly old globular clusters while NGC 3115 and NGC 3377 show a range of globular ages. This diversity implies different galaxy formation histories and that the globular cluster optical colour-metallicity relation is not universal as is commonly assumed in globular cluster studies. We find a correlation between the median age of the metal rich globular cluster populations and the age of the field star populations, in line with models where globular cluster formation is a natural outcome of high intensity star formation., 12 pages, 6 figures. Accepted for publication in the Monthly Notices of the Royal Astronomical Society

The formation histories of globular clusters (GCs) are a key diagnostic for understanding their relation to the evolution of the Universe through cosmic time. We use the suite of 25 cosmological zoom-in simulations of present-day Milky Way-mass galaxies from the E-MOSAICS project to study the formation histories of stars, clusters, and GCs, and how these are affected by the environmental dependence of the cluster formation physics. We find that the median lookback time of GC formation in these galaxies is ${\sim}10.73~$Gyr ($z=2.1$), roughly $2.5~$Gyr earlier than that of the field stars (${\sim}8.34~$Gyr or $z=1.1$). The epoch of peak GC formation is mainly determined by the time evolution of the maximum cluster mass, which depends on the galactic environment and largely increases with the gas pressure. Different metallicity subpopulations of stars, clusters and GCs present overlapping formation histories, implying that star and cluster formation represent continuous processes. The metal-poor GCs ($-2.5, Comment: 15 pages, 6 figures; accepted by MNRAS (April 30, 2019)

Recent work indicates that the nearby Galactic halo is dominated by the debris from a major accretion event. We confirm that result from an analysis of APOGEE-DR14 element abundances and $\textit{Gaia}$-DR2 kinematics of halo stars. We show that $\sim$2/3 of nearby halo stars have high orbital eccentricities ($e \gtrsim 0.8$), and abundance patterns typical of massive Milky Way dwarf galaxy satellites today, characterised by relatively low [Fe/H], [Mg/Fe], [Al/Fe], and [Ni/Fe]. The trend followed by high $e$ stars in the [Mg/Fe]-[Fe/H] plane shows a change of slope at [Fe/H]$\sim-1.3$, which is also typical of stellar populations from relatively massive dwarf galaxies. Low $e$ stars exhibit no such change of slope within the observed [Fe/H] range and show slightly higher abundances of Mg, Al and Ni. Unlike their low $e$ counterparts, high $e$ stars show slightly retrograde motion, make higher vertical excursions and reach larger apocentre radii. By comparing the position in [Mg/Fe]-[Fe/H] space of high $e$ stars with those of accreted galaxies from the EAGLE suite of cosmological simulations we constrain the mass of the accreted satellite to be in the range $10^{8.5}\lesssim M_*\lesssim 10^{9}\mathrm{M_\odot}$. We show that the median orbital eccentricities of debris are largely unchanged since merger time, implying that this accretion event likely happened at $z\lesssim1.5$. The exact nature of the low $e$ population is unclear, but we hypothesise that it is a combination of $\textit{in situ}$ star formation, high $|z|$ disc stars, lower mass accretion events, and contamination by the low $e$ tail of the high $e$ population. Finally, our results imply that the accretion history of the Milky Way was quite unusual., 19 Pages, 11 Figures (+4 in abstracts), Accepted for publication in MNRAS. ** Important new additions include an appendix showing numerical convergence tests, and a new figure and accompanying text demonstrating the consistency in element abundances between accreted satellites in EAGLE and the high eccentricity stars from APOGEE **

The recent discovery of super-massive black holes (SMBHs) in the centers of high-mass ultra compact dwarf galaxies (UCDs) suggests that at least some UCDs are the stripped nuclear star clusters of lower mass galaxies. Tracing these former nuclei of stripped galaxies provides a unique way to track the assembly history of a galaxy or galaxy cluster. In this paper we present a new method to estimate how many UCDs host an SMBH in their center and thus are stripped galaxy nuclei. We revisit the dynamical mass measurements that suggest many UCDs have more mass than expected from stellar population estimates, which recent observations have shown is due to the presence of an SMBH. We revise the stellar population mass estimates using a new empirical relation between the mass-to-light ratio (M/L) and metallicity, and use this to predict which UCDs are most likely to host an SMBH. This enables us to calculate the fraction of UCDs that host SMBHs across their entire luminosity range for the first time. We then apply the SMBH occupation fraction to the observed luminosity function of UCDs and estimate that in the Fornax and Virgo cluster alone there should be $69^{+32}_{-25}$ stripped nuclei with SMBHs. This analysis shows that stripped nuclei with SMBHs are almost as common in clusters as present-day galaxy nuclei. We estimate the local SMBH number density in stripped nuclei to $3-8\times10^{-3}Mpc^{-3}$, which represents a significant fraction (10-40\%) of the SMBH density in the local Universe. These SMBHs hidden in stripped nuclei will increase expected event rates for tidal disruption events and SMBH-SMBH and SMBH-BH mergers. The existence of numerous stripped nuclei with SMBHs are a direct consequence of hierarchical galaxy formation, but until now their impact on the SMBH density had not been quantified., 15 pages, 8 Figures, accepted for publication in ApJ

Several models have been advanced to explain the multiple stellar populations observed in globular clusters (GCs). Most models necessitate a large initial population of unenriched stars that provide the pollution for an enriched population, and which are subsequently lost from the cluster. This scenario generally requires clusters to lose $>90$ per cent of their birth mass. We use a suite of 25 cosmological zoom-in simulations of present-day Milky Way-mass galaxies from the \emosaics project to study whether dynamical disruption by evaporation and tidal shocking provides the necessary mass loss. We find that GCs with present-day masses $M>10^5~M_{\odot}$ were only $2$-$4$ times more massive at birth, in conflict with the requirements of the proposed models. This factor correlates weakly with metallicity, gas pressure at birth, or galactocentric radius, but increases towards lower GC masses. To reconcile our results with observational data, either an unphysically steep cluster mass-size relation must be assumed, or the initial enriched fractions must be similar to their present values. We provide the required relation between the initial enriched fraction and cluster mass. Dynamical cluster mass loss cannot reproduce the high observed enriched fractions nor their trend with cluster mass., 6 pages, 4 figures; accepted by MNRAS (September 4, 2018)

The metal-poor sub-population of globular cluster (GC) systems exhibits a correlation between the GC average colour and luminosity, especially in those systems associated with massive elliptical galaxies. More luminous (more massive) GCs are typically redder and hence more metal-rich. This 'blue tilt' is often interpreted as a mass-metallicity relation stemming from GC self-enrichment, whereby more massive GCs retain a greater fraction of the enriched gas ejected by their evolving stars, fostering the formation of more metal-rich secondary generations. We examine the E-MOSAICS simulations of the formation and evolution of galaxies and their GC populations, and find that their GCs exhibit a colour-luminosity relation similar to that observed in local galaxies, without the need to invoke mass-dependent self-enrichment. We find that the blue tilt is most appropriately interpreted as a dearth of massive, metal-poor GCs: the formation of massive GCs requires high interstellar gas surface densities, conditions that are most commonly fostered by the most massive, and hence most metal rich, galaxies, at the peak epoch of GC formation. The blue tilt is therefore a consequence of the intimate coupling between the small-scale physics of GC formation and the evolving properties of interstellar gas hosted by hierarchically-assembling galaxies., 24 pages, 11 figures. Accepted for publication in the Monthly Notices of the Royal Astronomical Society

We discuss some of the key open questions regarding the formation and evolution of globular clusters (GCs) during galaxy formation and assembly within a cosmological framework. The current state-of-the-art for both observations and simulations is described, and we briefly mention directions for future research. The oldest GCs have ages $\ge$ 12.5 Gyr and formed around the time of reionisation. Resolved colour-magnitude diagrams of Milky Way GCs and direct imaging of lensed proto-GCs at z $\sim$ 6 with JWST promise further insight. Globular clusters are known to host multiple populations of stars with variations in their chemical abundances. Recently, such multiple populations have been detected in $\sim$2 Gyr old compact, massive star clusters. This suggests a common, single pathway for the formation of GCs at high and low redshift. The shape of the initial mass function for GCs remains unknown, however for massive galaxies a power-law mass function is favoured. Significant progress has been made recently modelling GC formation in the context of galaxy formation, with success in reproducing many of the observed GC-galaxy scaling relations., Comment: 28 pages, accepted for publication in the Proceedings of the Royal Society A journal. Version 2 with updated references

Ultra Compact Dwarf Galaxies (UCDs) and dwarf galaxy nuclei have many common properties, such as internal velocity dispersions and colour-magnitude trends, suggesting tidally stripped dwarf galaxies as a possible UCD origin. However, UCDs typically have sizes more than twice as large as nuclei at the same luminosity. We use a GPU-enabled version of the particle-mesh code \textsc{superbox} to study the possibility of turning nucleated dwarf galaxies into UCDs by tidally stripping them in a Virgo-like galaxy cluster. We find that motion in spherical potentials, where close passages happen many times, leads to the formation of compact ($r_h \lesssim 20$ pc) star clusters/UCDs. In contrast, orbital motion where close passages happen only once or twice leads to the formation of extended objects which are large enough to account for the full range of observed UCD sizes. For such motion, we find that dwarf galaxies need close pericentre passages with distances less than 10 kpc to undergo strong enough stripping so that UCD formation is possible. As tidal stripping produces objects with similar properties to UCDs, and our estimates suggest dwarf galaxies have been destroyed in sufficient numbers to explain the observed number of UCDs in M87, we consider tidal stripping to be a likely origin of UCDs. However, comparison with cosmological simulations is needed to determine if the number and spatial distribution of UCDs formed by tidal stripping matches the observations of UCDs in galaxy clusters., Comment: 10 pages, 5 figures, accepted for publication in MNRAS

We compare the predictions of a semi-analytic model for ultra-compact dwarf galaxy (UCD) formation by tidal stripping to the observed properties of globular clusters (GCs) and UCDs in the Fornax and Virgo clusters. For Fornax we find the predicted number of stripped nuclei agrees very well with the excess number of GCs$+$UCDs above the GC luminosity function. GCs$+$UCDs with masses $>10^{7.3}$ M$_\odot$ are consistent with being entirely formed by tidal stripping. Stripped nuclei can also account for Virgo UCDs with masses $>10^{7.3}$ M$_\odot$ where numbers are complete by mass. For both Fornax and Virgo, the predicted velocity dispersions and radial distributions of stripped nuclei are consistent with that of UCDs within $\sim$50-100 kpc but disagree at larger distances where dispersions are too high and radial distributions too extended. Stripped nuclei are predicted to have radially biased anisotropies at all radii, agreeing with Virgo UCDs at clustercentric distances larger than 50 kpc. However, ongoing disruption is not included in our model which would cause orbits to become tangentially biased at small radii. We find the predicted metallicities and central black hole masses of stripped nuclei agree well with the metallicities and implied black hole masses of UCDs for masses $>10^{6.5}$ M$_\odot$. The predicted black hole masses also agree well with that of M60-UCD1, the first UCD with a confirmed central black hole. These results suggest that observed GC$+$UCD populations are a combination of genuine GCs and stripped nuclei, with the contribution of stripped nuclei increasing toward the high-mass end., 18 pages, 12 figures, accepted for publication in MNRAS

Ultra-compact dwarf galaxies (UCDs) are intermediate objects between globular clusters and dwarf galaxies, with many similarities to the nuclear clusters of dwarf galaxies. Tidal stripping of nucleated galaxies is a likely origin for UCDs since tidal stripping must occur in any hierarchical galaxy formation scenario. During the tidal stripping process the main body of the galaxy is removed while the nucleus remains since the nuclear clusters are too compact to be destroyed. In this thesis I present new theoretical work addressing the possibility of UCDs having a tidal stripping origin. Through the use of N-body simulations I show that tidal stripping of nucleated galaxies in galaxy clusters under the assumption of dark matter free galaxies can account for the observed sizes and masses of UCDs. I find that incomplete stripping of the UCD progenitor galaxy, resulting in a UCD with an extended stellar envelope, may account for the observed size difference between nuclear clusters and UCDs. In a second study, I use a semi-analytic model of galaxy formation to predict the number of UCDs expected to form via tidal stripping. I find that tidal stripping cannot account for all UCDs observed in the Fornax cluster but is most important for high mass UCDs, accounting for about 50 per cent of objects with masses larger than 107M☉. Additionally, I compare the predictions for radial distributions, metallicities and implied central black hole masses from the semi-analytic models with observed UCDs in the Fornax and Virgo clusters, finding good agreement between the predictions and observations. This work suggest most UCDs are simply high-mass globular clusters, with the most massive and extended UCDs being formed by tidal stripping. Finally, I present a new method to incorporate tidal stripping of satellite galaxies into semi-analytic models of galaxy formation. Comparing with observed dwarf galaxies in the Fornax cluster, I find this method gives better agreement with the predicted numbers and radial distributions of galaxies when compared with models not taking into account tidal stripping.

We use the Millennium II cosmological simulation combined with the semi-analytic galaxy formation model of Guo et al. (2011) to predict the contribution of galactic nuclei formed by the tidal stripping of nucleated dwarf galaxies to globular cluster (GC) and ultra-compact dwarf galaxy (UCD) populations of galaxies. We follow the merger trees of galaxies in clusters back in time and determine the absolute number and stellar masses of disrupted galaxies. We assume that at all times nuclei have a distribution in nucleus-to-galaxy mass and nucleation fraction of galaxies similar to that observed in the present day universe. Our results show stripped nuclei follow a mass function $N(M) \sim M^{-1.5}$ in the mass range $10^6 < M/M_\odot < 10^8$, significantly flatter than found for globular clusters. The contribution of stripped nuclei will therefore be most important among high-mass GCs and UCDs. For the Milky Way we predict between 1 and 3 star clusters more massive than $10^5 M_\odot$ come from tidally disrupted dwarf galaxies, with the most massive cluster formed having a typical mass of a few times $10^6 M_\odot$, like omega Centauri. For a galaxy cluster with a mass $7 \times 10^{13} M_\odot$, similar to Fornax, we predict $\sim$19 UCDs more massive than $2\times10^6 M_\odot$ and $\sim$9 UCDs more massive than $10^7 M_\odot$ within a projected distance of 300 kpc come from tidally stripped dwarf galaxies. The observed number of UCDs are $\sim$200 and 23, respectively. We conclude that most UCDs in galaxy clusters are probably simply the high mass end of the GC mass function., 15 pages, 9 figures, accepted for publication in MNRAS

We present a detailed comparison of the Milky Way (MW) globular cluster (GC) kinematics with the 25 Milky Way-mass cosmological simulations from the E-MOSAICS project. While the MW falls within the kinematic distribution of GCs spanned by the simulations, the relative kinematics of its metal-rich ($[\rm{Fe/H}]>-1.2$) versus metal-poor ($[\rm{Fe/H}]8\rm{kpc}$) populations are atypical for its mass. To understand the origins of these features, we perform a comprehensive statistical analysis of the simulations, and find 18 correlations describing the assembly of $L^*$ galaxies and their dark matter haloes based on their GC population kinematics. The correlations arise because the orbital distributions of accreted and in-situ GCs depend on the masses and accretion redshifts of accreted satellites, driven by the combined effects of dynamical fraction, tidal stripping, and dynamical heating. Because the kinematics of in-situ/accreted GCs are broadly traced by the metal-rich/metal-poor and inner/outer populations, the observed GC kinematics are a sensitive probe of galaxy assembly. We predict that relative to the population of $L^*$ galaxies, the MW assembled its dark matter and stellar mass rapidly through a combination of in-situ star formation, more than a dozen low-mass mergers, and $1.4\pm1.2$ early ($z=3.1\pm1.3$) major merger. The rapid assembly period ended early, limiting the fraction of accreted stars. We conclude by providing detailed quantitative predictions for the assembly history of the MW., Comment: 24 pages, 20 figures. Published in MNRAS

Globular clusters (GCs) formed when the Milky Way experienced a phase of rapid assembly. We use the wealth of information contained in the Galactic GC population to quantify the properties of the satellite galaxies from which the Milky Way assembled. To achieve this, we train an artificial neural network on the E-MOSAICS cosmological simulations of the co-formation and co-evolution of GCs and their host galaxies. The network uses the ages, metallicities, and orbital properties of GCs that formed in the same progenitor galaxies to predict the stellar masses and accretion redshifts of these progenitors. We apply the network to Galactic GCs associated with five progenitors: {\it Gaia}-Enceladus, the Helmi streams, Sequoia, Sagittarius, and the recently discovered, `low-energy' GCs, which provide an excellent match to the predicted properties of the enigmatic galaxy `Kraken'. The five galaxies cover a narrow stellar mass range [$M_\star=(0.6{-}4.6)\times10^8~{\rm M}_\odot$], but have widely different accretion redshifts ($z_{\rm acc}=0.57{-}2.65$). All accretion events represent minor mergers, but Kraken likely represents the most major merger ever experienced by the Milky Way, with stellar and virial mass ratios of $r_{M_\star}=1$:$31^{+34}_{-16}$ and $r_{M_{\rm h}}=1$:$7^{+4}_{-2}$, respectively. The progenitors match the $z=0$ relation between GC number and halo virial mass, but have elevated specific frequencies, suggesting an evolution with redshift. Even though these progenitors likely were the Milky Way's most massive accretion events, they contributed a total mass of only $\log{(M_{\rm \star,tot}/{\rm M}_\odot)}=9.0\pm0.1$, similar to the stellar halo. This implies that the Milky Way grew its stellar mass mostly by in-situ star formation. We conclude by organising these accretion events into the most detailed reconstruction to date of the Milky Way's merger tree., Comment: 20 pages, 9 figures, 2 tables; submitted to MNRAS (March 1, 2020); Figures 4, 5, and 9 show the main results of the paper

Stellar haloes encode a fossil record of a galaxy's accretion history, generally in the form of structures of low surface brightness, such as stellar streams. While their low surface brightness makes it challenging to determine their age, metallicity, kinematics and spatial structure, the infalling galaxies also deposit globular clusters (GCs) in the halo, which are bright and therefore easier to observe and characterise. To understand how GCs associated with stellar streams can be used to estimate the stellar mass and the infall time of their parent galaxy, we examine a subset of 15 simulations of galaxies and their star clusters from the E-MOSAICS project. E-MOSAICS is a suite of hydrodynamical simulations incorporating a sub-grid model for GC formation and evolution. We find that more massive accreted galaxies typically contribute younger and more metal rich GCs. This lower age results from a more extended cluster formation history in more massive galaxies. In addition, at fixed stellar mass, galaxies that are accreted later host younger clusters, because they can continue to form GCs without being subjected to environmental influences for longer. This explains the large range of ages observed for clusters associated with the Sagittarius dwarf galaxy in the halo of the Milky Way compared to clusters which are thought to have formed in satellites accreted early in the Milky Way's formation history. Using the ages of the GCs associated with the Sagittarius dwarf, we estimate a virial radius crossing lookback time (infall time) of $9.3 \pm 1.8 Gyr$., Accepted to MNRAS

Dynamical models allow us to connect the motion of a set of tracers to the underlying gravitational potential, and thus to the total (luminous and dark) matter distribution. They are particularly useful for understanding the mass and spatial distribution of dark matter (DM) in a galaxy. Globular clusters (GCs) are an ideal tracer population in dynamical models, since they are bright and can be found far out into the halo of galaxies. We aim to test how well Jeans-Anisotropic-MGE (JAM) models using GCs (positions and line-of-sight velocities) as tracers can constrain the mass and radial distribution of DM halos. For this, we use the E-MOSAICS suite of 25 zoom-in simulations of L* galaxies. We find that the DM halo properties are reasonably well recovered by the JAM models. There is, however, a strong correlation between how well we recover the mass and the radial distribution of the DM and the number of GCs in the galaxy: the constraints get exponentially worse with fewer GCs, and at least 150 GCs are needed in order to guarantee that the JAM model will perform well. We find that while the data quality (uncertainty on the radial velocities) can be important, the number of GCs is the dominant factor in terms of the accuracy and precision of the measurements. This work shows promising results for these models to be used in extragalactic systems with a sample of more than 150 GCs., 18 pages, 13 figures. Accepted for publication in MNRAS