Where did the globular clusters of the Milky Way form? Insights from the E-MOSAICS simulations
Benjamin W. Keller, J. M. Diederik Kruijssen, Joel Pfeffer, Marta Reina-Campos, Nate Bastian, Sebastian Trujillo-Gomez, Meghan E. Hughes, Robert A. Crain
备注：
20 pages, 20 figures, resubmitted to MNRAS after accounting for referee's comments
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.
It has been a long-standing open question why observed globular cluster (GC) populations of different metallicities differ in their ages and spatial distributions, with metal-poor GCs being the older and radially more extended of the two. We use the suite of 25 Milky Way-mass cosmological zoom-in simulations from the E-MOSAICS project, which self-consistently model the formation and evolution of stellar clusters and their host galaxies, to understand the properties of observed GC populations. We find that the different ages and spatial distributions of metal-poor and metal-rich GCs are the res…
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 go 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…
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 t…
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 \si…
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 …
We present 25 cosmological zoom-in simulations of Milky Way-mass galaxies in the `MOdelling Star cluster population Assembly In Cosmological Simulations within EAGLE' (E-MOSAICS) project. E-MOSAICS couples a detailed physical model for the formation, evolution, and disruption of star clusters to the EAGLE galaxy formation simulations. This enables following the co-formation and co-evolution of galaxies and their star cluster populations, thus realising the long-standing promise of using globular clusters (GCs) as tracers of galaxy formation and assembly. The simulations show that the age-metal…
We summarize the results presented in Krause et al. (2012) on the impact of supernova-driven shells and dark-remnant accretion on gas expulsion in globular cluster infancy.
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 matte…
We study the present-day rotational velocity ($V_{rot}$) and velocity dispersion ($σ$) 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…
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 (${\s…
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 spannin…
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 ($[\rm{Fe/H}]<-1.2$), and inner ($r<8\rm{kpc}$) versus outer ($r>8\rm{kpc}$) 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 describin…
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. …
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 simulatio…
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…
Globular clusters (GCs) are bright objects that span a wide range of galactocentric distances, and are thus probes of the structure of dark matter (DM) haloes. In this work, we explore whether the projected radial profiles of GCs can be used to infer the structural properties of their host DM haloes. We use the simulated GC populations in a sample of 166 central galaxies from the $(34.4~\rm cMpc)^3$ periodic volume of the E-MOSAICS project. We find that more massive galaxies host stellar and GC populations with shallower density profiles that are more radially extended. In addition, the metal-…
Faint fuzzies are a relatively new class of star cluster, first found in the nearby S0 galaxy NGC 1023 by Larsen & Brodie using WFPC2 images from the Hubble Space Telescope (HST). Here we investigate the star cluster system of NGC 1023 using an eight pointing mosaic of ACS images from HST. We identify blue and red normal globular clusters (two of which are particularly luminous and dense) and two ultra compact dwarf objects (with effective radius ~10 pc). With our more complete spatial coverage, we also find 81 red and 27 blue faint fuzzies (FFs). We confirm the association of the red FFs with…
We present HST/ACS $g$ and $z$ photometry and half-light radii $R_{\rm h}$ measurements of 360 globular cluster (GC) candidates around the nearby S0 galaxy NGC 3115. We also include Subaru/Suprime-Cam $g$, $r$, and $i$ photometry of 421 additional candidates. The well-established color bimodality of the GC system is obvious in the HST/ACS photometry. We find evidence for a "blue tilt" in the blue GCs, wherein the blue GCs get redder as luminosity increases, indicative of a mass-metallicity relationship. We find a color gradient in both the red and blue subpopulations, with each group of cluste…
Using astrometric techniques developed by Anderson et al., we determine proper motions (PMs) in 14.60 arcmin X 16.53 arcmin area of the kinematically "thick-disk" globular cluster M12. The cluster's proximity and sparse nature makes it a suitable target for ground-based telescopes. Archive images with time gap of 11.1 years were observed with wide-field imager (WFI) mosaic camera mounted on ESO 2.2 m telescope. The median value of PM error in both components is 0.7 mas/yr for the stars having V less than or equal to 20 mag. PMs are used to determine membership probabilities and to separate fie…
The masses of supermassive black holes (SMBHs, M_BH=10^6-10^11 Msun) in the centres of galaxies are related to the host stellar spheroid mass and velocity dispersion. A key question is how these relations originate, and over which range of black hole masses they hold. It has been speculated that intermediate-mass black holes (IMBHs, M_BH=10^2-10^5 Msun) could play a fundamental role in the growth of SMBHs. A handful of IMBHs has recently been detected in Galactic globular clusters (GCs), but their masses are inconsistent with the galactic scaling relations of SMBHs. In this Letter, we derive t…
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 populatio…
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 include…
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 subse…
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 los…
This is a "biased" review because I will show recent evidence on the contribution of globular clusters (GCs) to the halo of our Galaxy seen through the lens of the new paradigm of multiple populations in GCs. I will show a few examples where the chemistry of multiple populations helps to answer hot questions including whether and how much GCs did contribute to the halo population, if we have evidence of the GCs-halo link, what are the strengths and weak points concerning this contribution.
The mass function of globular cluster (GC) populations is a fundamental observable that encodes the physical conditions under which these massive stellar clusters formed and evolved. The high-mass end of star cluster mass functions are commonly described using a Schechter function, with an exponential truncation mass $M_{c,*}$. For the GC mass functions in the Virgo galaxy cluster, this truncation mass increases with galaxy mass ($M_{*}$). In this paper we fit Schechter mass functions to the GCs in the most massive galaxy group ($M_{\mathrm{200}} = 5.14 \times 10^{13} M_{\odot}$) in the E-MOSA…
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 it…
NGC 4753 is a bright (M_V approx -22.3) lenticular galaxy. It is a very interesting target to test different theories of formation of lenticular galaxies, due to its low-density environment and complex structure. We perform the first comprehensive study of NGC 4753 globular cluster system (GCS), using Gemini/GMOS and CTIO/MosaicII images. Our results indicate a rather poor GCS of approx 1000 members. Its azimuthal distribution follows the shape of the galaxy bulge. The GC colour distribution is peculiar, presenting an intermediate subpopulation in addition to blue and red ones. This intermedia…
Once fixed the age and metallicity; the colour distribution of horizontal branch stars in a globular cluster depends on few parameters: the helium abundance of the population and the mass lost during the pre-HB stages. These parameters are usually derived from the HB itself, hence they are degenerate. Breaking this degeneracy and understanding their role is a tricky and challenging problem that no study has tried to solve yet. Combining the information obtained from the chromosome maps and the analysis of multi-band photometry with state of the art stellar evolution models, we can obtain a sol…
Recently, new Sagittarius (Sgr) dwarf galaxy globular clusters were discovered, which opens the question on the actual size of the Sgr globular cluster population, and therefore on our understanding of the Sgr galaxy formation and accretion history onto the Milky Way. Based on Gaia EDR3 and SDSS IV DR16 (APOGEE-2) data sets, we performed an analysis of the color-magnitude diagrams (CMDs) of the eight new Sgr globular clusters found by from a sound cleaning of the contamination of Milky Way and Sgr field stars, complemented by Minniti et al. (2021b) available kinematic and metal abundance infor…
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 prog…
We present a study of the spatial and color distributions of four early-type galaxies and their globular cluster (GC) systems observed as part of our ongoing wide-field imaging survey. We use $BVR$ KPNO-4m+MOSAIC imaging data to characterize the galaxies' GC populations, perform surface photometry of the galaxies, and compare the projected two-dimensional shape of the host galaxy light to that of the GC population. The GC systems of the ellipticals NGC 4406 and NGC 5813 both show an elliptical distribution consistent with that of the host galaxy light. Our analysis suggests a similar result fo…
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 distrib…
There are only about 65 R Coronae Borealis stars known in our Galaxy, and none in globular clusters. As these stars are thought to result from the merger of two white dwarfs, one would expect the higher stellar density of globular clusters to favor their formation. We have searched for such stars in Galactic globular clusters, as their presence in a specific category of clusters might provide more clues as to their formation. We selected from the WISE all-Sky source catalog all the stars within the tidal radius of the 150 globular clusters within 50 kpc, which is the distance to which RCB star…
We use our Galactic Globular Cluster Catalog (G2C2) photometry for 111 Galactic globular clusters (GC) in g and z, as well as r and i photometry for a subset of 60 GCs and u photometry for 22 GCs, to determine the structural parameters assuming King (1962) models. In general, the resulting core radii are in good comparison with the current literature values. However, our half-light radii are slightly lower than the literature. The concentrations (and therefore also the tidal radii) are poorly constrained mostly because of the limited radial extent of our imaging. Therefore, we extensively disc…
We here present the luminosity function (LF) of globular clusters (GCs) in five nearby spiral galaxies using the samples of GC candidates selected in Hubble Space Telescope mosaic images in F435W, F555W and F814W filters. Our search, which surpasses the fractional area covered by all previous searches in these galaxies, has resulted in the detection of 158 GC candidates in M81, 1123 in M101, 226 in NGC4258, 293 in M51 and 173 in NGC628. The LFs constructed from this dataset, after correcting for relatively small contamination from reddened young clusters, are log-normal in nature, which was hi…
We take advantage of exquisitely deep optical imaging data from HST/ACS in the F475W ($g_{F475W}$) and F606W ($V_{F606W}$) bands, to study the properties of the globular cluster (GC) population in the intermediate mass lenticular galaxy PGC 087327, in the Hydra I galaxy cluster. We inspect the photometric (magnitudes and color) and morphometric (compactness, elongation, etc.) properties of sources lying in an area of $\sim19\times19$ kpc centered on PGC 087327, and compare them with four neighbouring fields over the same HST/ACS mosaic. This allowed us to identify a list of GC candidates and t…
Globular clusters (GCs) are powerful tracers of the galaxy assembly process, and have already been used to obtain a detailed picture of the progenitors of the Milky Way. Using the E-MOSAICS cosmological simulation of a (34.4 Mpc)$^3$ volume that follows the formation and co-evolution of galaxies and their star cluster populations, we develop a method to link the origin of GCs to their observable properties. We capture this complex link using a supervised deep learning algorithm trained on the simulations, and predict the origin of individual GCs (whether they formed in the main progenitor or w…
Nantais et al. used the Hubble Space Telescope to localize probable globular clusters (GCs) in M81, a spiral galaxy at a distance of 3.63 Mpc. Theory predicts that GCs can host intermediate-mass black holes (IMBHs) with masses M_BH \sim 100 - 100,000 M_sun. Finding IMBHs in GCs could validate a formation channel for seed BHs in the early universe, bolster gravitational-wave predictions for space missions, and test scaling relations between stellar systems and the central BHs they host. We used the NRAO Karl G. Jansky Very Large Array (VLA) to search for the radiative signatures of IMBH accreti…
We present new wide-field photometry and spectroscopy of the globular clusters (GCs) around NGC 4649 (M60), the third brightest galaxy in the Virgo cluster. Imaging of NGC 4649 was assembled from a recently-obtained HST/ACS mosaic, and new Subaru/Suprime-Cam and archival CFHT/MegaCam data. About 1200 sources were followed up spectroscopically using combined observations from three multi-object spectrographs: Keck/DEIMOS, Gemini/GMOS and MMT/Hectospec. We confirm 431 unique GCs belonging to NGC 4649, a factor of 3.5 larger than previous datasets and with a factor of 3 improvement in velocity pr…
We investigate possible relations between the abundances of zinc and the light elements sodium, magnesium, and potassium in the atmospheres ofred giant branch (RGB) stars of the Galactic globular cluster 47~Tuc and study connections between the chemical composition and dynamical properties of the cluster RGB stars. The abundance of zinc was determined in 27 RGB stars of 47~Tuc using 1D local thermal equilibrium (LTE) synthetic line profile fitting to the high-resolution 2dF spectra obtained with the Anglo-Australian Telescope (AAT). Synthetic spectra used in the fitting procedure were computed…
We present Keck/DEIMOS spectroscopy of stars in the recently discovered Milky Way satellites Hydra II, Pisces II, and Laevens 1. We measured a velocity dispersion of 5.4 (+3.6 -2.4) km/s for Pisces II, but we did not resolve the velocity dispersions of Hydra II or Laevens 1. We marginally resolved the metallicity dispersions of Hydra II and Pisces II but not Laevens 1. Furthermore, Hydra II and Pisces II obey the luminosity-metallicity relation for Milky Way dwarf galaxies (<[Fe/H]> = -2.02 +/- 0.08 and -2.45 +/- 0.07, respectively), whereas Laevens 1 does not (<[Fe/H]> = -1.68 +/- 0.05). The …
We present g and z photometry and size estimates for globular clusters (GCs) in the massive Virgo elliptical NGC 4649 (M60) using a five-pointing Hubble Space Telescope/Advanced Camera for Surveys mosaic. The metal-poor GCs show a monotonic negative metallicity gradient of (-0.43 +/- 0.10) dex per dex in radius over the full radial range of the data, out to ~ 24 kpc. There is evidence for substantial color substructure among the metal-rich GCs. The metal-poor GCs have typical sizes ~ 0.4 pc larger than the metal-rich GCs out to large galactocentric distances (~> 20 kpc), favoring an intrinsic …
We present an implementation of the matched-filter technique to detect tidal tails of globular clusters. The method was tested using SDSS data for the globular cluster Palomar 5 revealing its well known tidal tails. We also ran a simulation of a globular cluster with a tidal tail where we successfully recover the tails for a cluster at the same position and with the same characteristics of NGC 2298. Based on the simulation we estimate that the matched-filter increases the contrast of the tail relative to the background of stars by a factor of 2.5 for the case of NGC 2298. We also present the p…
Aluminum is the heaviest light element displaying large star--to--star variations in Galactic globular clusters (GCs). This element may provide additional insight into the origin of the multiple populations now known to be a common place in GCs, and also the nature of the first-generation stars responsible for a cluster's chemical inhomogeneities. In a previous analysis we found that, unlike more metal-poor GCs, 47 Tuc did not exhibit a strong Na-Al correlation, which motivates a careful study of the similar metallicity but less massive GC M71. We present chemical abundances of O, Na, Al, and …
We present the X-ray luminosity function (XLF) of low mass X-ray binaries (LMXBs) in the globular clusters (GCs) and fields of seven early-types galaxies. These galaxies are selected to have both deep Chandra observations, which allow their LMXB populations to be observed to X-ray luminosities of $10^{37}-10^{38}$ erg/s, and HST optical mosaics which enable the X-ray sources to be separated into field LMXBs, GC LMXBs, and contaminating background and foreground sources. We find that at all luminosities the number of field LMXBs per stellar mass is similar in these galaxies. This suggests that …
We compare the results on the chemical composition of four globular clusters (GCs) in M31 (Bol 6, Bol 20, Bol 45, and Bol 50) (Maricheva M. 2021). Study of integrated spectra of four globular clusters in M31. Astrophys. Bull. 76:389-404. doi: https://doi.org/10.1134/S199034132104009X) to the available literature data on integrated-light spectroscopy of GCs with similar ages and chemical abundances in our Galaxy and M31 and on the chemical abundances of stars in two galaxies. The clusters and their literature analogues are of moderate metallicity -1.1<[Fe/H]<-0.75 dex and old (10 Gyr). Mg, Ca, …
In the dense stellar environment of the globular clusters, compact binaries are produced dynamically. Therefore the fraction of type Ia supernovae that explode in globular clusters is expected to be higher than the fraction of mass residing in these. We have searched for globular clusters at the positions of observed type Ia supernovae. We used archival HST images and literature data, covering the positions either before the supernovae exploded, or long enough after that the supernovae have faded below the luminosities of globular clusters. We did not find evidence for globular clusters at any…
We present new number density and surface brightness profiles for the globular cluster M92 (NGC 6341). These profiles are calculated from optical images collected with the CCD mosaic camera MegaCam at the Canada-France-Hawaii-Telescope and with the Advanced Camera for Surveys on the Hubble Space Telescope. The ground-based data were supplemented with the Sloan Digital Sky Survey photometric catalog. Special care was taken to discriminate candidate cluster stars from field stars and to subtract the background contamination from both profiles. By examining the contour levels of the number densit…
An increasing body of data reveals a one-to-one linear correlation between galaxy halo mass and the total mass in its globular cluster (GC) population, M_{GCS} ~ M_h^{1.03 \pm 0.03}, valid over 5 orders of magnitude. We explore the nature of this correlation for galaxies of different morphological types, and for the subpopulations of metal-poor (blue) and metal-rich (red) GCs. For the subpopulations of different metallicity we find M_{GCS}(blue) ~ M_h^{0.96 \pm 0.03} and M_{GCS}(red) ~ M_h^{1.21 \pm 0.03} with similar scatter. The numerical values of these exponents can be derived from the det…
We explore how diffuse stellar light and globular clusters (GCs) can be used to trace the matter distribution of their host halo using an observational methodology. For this, we use 117 simulated dark matter (DM) haloes from the $(34.4~\rm cMpc)^3$ periodic volume of the E-MOSAICS project. For each halo, we compare the stellar surface brightness and GC projected number density maps to the surface densities of DM and total mass. We find that the dominant structures identified in the stellar light and in the GCs correspond closely with those from the DM and total mass. Our method is unaffected b…
Globular Clusters are among the oldest objects in the Galaxy, thus their researchers are key to understanding the processes of evolution and formation that the galaxy has experienced in early stages. Spectroscopic studies allow us to carry out detailed analyzes on the chemical composition of Globular Clusters. The aim of our research is to perform a detailed analysis of chemical abundances to a sample of stars of the Bulge Globular Cluster NGC 6553, in order to determine chemical patterns that allow us to appreciate the phenomenon of Multiple Population in one of the most metal-rich Globular C…
We have observed 15 red giant stars in the relatively massive, metal-poor globular cluster NGC 4833 using the Magellan Inamori Kyocera Echelle spectrograph at Magellan. We calculate stellar parameters for each star and perform a standard abundance analysis to derive abundances of 43 species of 39 elements, including 20 elements heavier than the iron group. We derive <[Fe/H]> = -2.25 +/- 0.02 from Fe I lines and <[Fe/H> = -2.19 +/- 0.013 from Fe II lines. We confirm earlier results that found no internal metallicity spread in NGC 4833, and there are no significant star-to-star abundance dispers…
We review the properties of globular clusters which make them useful for studying the Galactic halo, Galactic chemical evolution, and the early stages of the formation of the Milky Way. We review the evidence that GCs have a chemical inventory similar to those of halo field stars. We discuss the abundance ratios for dSph galaxies and show that it is possible to have formed at least part the Galactic halo field stellar population by dissolving globular clusters and/or accreting dSph galaxies but only if this occurred at an early stage in the formation of the Galaxy. We review the constraints on…
