Recent observations suggest the presence of supermassive black holes at the centers of many galaxies. The existence of intermediate-mass black holes (IMBHs) in globular clusters has also been predicted. We focus on gravitational lensing as a new way to explore these entities. It is known that the mass distribution of a self-gravitating system such as a globular cluster changes greatly depending on the presence or absence of a central massive object. After considering possible mass distributions for a globular cluster belonging to the Milky Way galaxy, we estimate that the effect on the separation angle of gravitational lensing due to an IMBH would be of milliarcsecond order.
Small distortions in the images of Einstein rings or giant arcs offer the exciting prospect of detecting dark matter haloes or subhaloes of mass below $10^9$M$_{\odot}$, most of which are too small to have made a visible galaxy. A very large number of such haloes are predicted to exist in the cold dark matter model of cosmogony; in contrast other models, such as warm dark matter, predict no haloes below a mass of this order which depends on the properties of the warm dark matter particle. Attempting to detect these small perturbers could therefore discriminate between different kinds of dark m…
Lensing flux-ratio anomalies have been frequently observed and taken as evidence for the presence of abundant dark matter substructures in lensing galaxies, as predicted by the cold dark matter (CDM) model of cosmogony. In previous work, we examined the cusp-caustic relations of the multiple images of background quasars lensed by galaxy-scale dark matter haloes, using a suite of high-resolution N-body simulations (the Aquarius simulations). In this work, we extend our previous calculations to incorporate both the baryonic and diffuse dark components in lensing haloes. We include in each lensin…
We propose a new formation channel for intermediate mass black hole (IMBH) binaries via globular cluster collisions in the Galactic disc. Using numerical simulations, we show that the IMBHs form a tight binary that enters the gravitational waves (GWs) emission dominated regime driven by stellar interactions, and ultimately merge in $\lesssim 0.5$ Gyr. These events are clearly audible to LISA and can be associated with electromagnetic emission during the last evolutionary stages. During their orbital evolution, the IMBHs produce runaway stars comparable with GAIA and LAMOST observations.
Modelling and Subtracting Diffuse Cluster Light in JWST Images: A Relation between the Spatial Distribution of Globular Clusters, Dwarf Galaxies, and Intracluster Light in the Lensing Cluster SMACS 0723
Intermediate-mass black holes are the missing link that connects stellar-mass to supermassive black holes and are key to understanding galaxy evolution. Gravitational waves, like photons, can be lensed, leading to discernable effects such as diffraction or repeated signals. We investigate the detectability of intermediate-mass black hole deflectors in the LIGO-Virgo detector network. In particular, we simulate gravitational waves with variable source distributions lensed by an astrophysical population of intermediate-mass black holes, and use standard LIGO tools to infer the properties of thes…
We present a photometric study of the isolated elliptical NGC 6411 and its globular cluster (GC) system, based on Gemini/GMOS g', r', i' photometry. This galaxy has been the host of a SNIa. Spectral studies indicate an intermediate-age and very metal-rich stellar population in its inner region. The extent of the globular cluster system is about 65 kpc. Its population contains $700\pm45$ members, implying a rather poor system, as normally found for isolated ellipticals. The colour bimodality and luminosity distribution are typical of old GC systems. An excess of bright GCs with intermediate col…
Using the Next Generation Very Large Array (ngVLA), we will make a comprehensive inventory of intermediate-mass black holes (IMBHs) in hundreds of globular cluster systems out to a distance of 25 Mpc. IMBHs have masses of about 100 to 100,000 solar masses. Finding them in globular clusters would validate a formation channel for seed black holes in the early universe and inform event predictions for gravitational wave facilities. Reaching a large number of globular clusters is key, as Fragione et al. (2018) predict that only a few percent will have retained their gravitational-wave fostering IM…
We present the results of combining Hubble Space Telescope optical photometry with ground-based Ks-band photometry from the Gemini imagers NIRI and FLAMINGOS-I to study the globular-cluster populations in four early-type galaxies that are candidate remnants of recent mergers (NGC1700, NGC2865, NGC4382, and NGC7727). These galaxies were chosen based on their blue colors and fine structure, such as shells and ripples that are indicative of past interactions. We fit the combined VIKs globular-cluster data with simple toy models of mixed cluster populations that contain three subpopulations of dif…
JWST's PEARLS: 119 multiply imaged galaxies behind MACS0416, lensing properties of caustic crossing galaxies, and the relation between halo mass and number of globular clusters at $z=0.4$
In this paper, we address the question: What is the probability of stellar-mass black hole (BH) binaries co-existing in a globular cluster with an intermediate-mass black hole (IMBH)? Our results suggest that the detection of one or more BH binaries can strongly constrain the presence of an IMBH in most Galactic globular clusters. More specifically, the detection of one or more BH binaries could strongly indicate against the presence of an IMBH more massive than $\gtrsim 10^3$ M$_{\rm \odot}$ in roughly 80\% of the clusters in our sample. To illustrate this, we use a combination of N-body simu…
AGB stars have long been held responsible for the important star-to-star variations in light elements observed in Galactic globular clusters. We analyse the main impacts of a first generation of rotating intermediate-mass stars on the chemical properties of second-generation globular cluster stars. The rotating models were computed without magnetic fields and without the effects of internal gravity waves. They account for the transports by meridional currents and turbulence. We computed the evolution of both standard and rotating stellar models with initial masses between 2.5 and 8 Msun within…
NGC 2419 is one of the remotest star clusters in the Milky Way halo and its exact nature is yet unclear: While it has traits reminiscent of a globular cluster (GC), its large radius and suggestions of an abundance spread have fueled the discussion about its origin in an extragalactic environment, possibly the remnants of the accretion of a dwarf galaxy. Here, we present first results from deep intermediate-band photometry of NGC 2419, which enables us to search for chemical (light element) abundance variations, metallicity spreads, and thus multiple stellar populations through well calibrated …
We discuss the potential of the gravitational microlensing method as a unique tool to detect unambiguous signals caused by intermediate-mass black holes in globular clusters. We select clusters near the line of sight to the Galactic Bulge and the Small Magellanic Cloud, estimate the density of background stars for each of them, and carry out simulations in order to estimate the probabilities of detecting the astrometric signatures caused by black hole lensing. We find that for several clusters, the probability of detecting such an event is significant with available archival data from the Hubb…
Context. The chemical processes during the Asymptotic Giant Branch (AGB) evolution of intermediate mass single stars predict most of the observations of the different populations in globular clusters although some important issues still need to be further clarified. In particular, to reproduce the observed anticorrelations of Na-O and Al-Mg, chemically enriched gas lost during the AGB phase of intermediate mass single stars must be mixed with matter with a pristine chemical composition. The source of this matter is still a matter of debate. Furthermore, observations reveal that a significant f…
Globular clusters have been alternatively predicted to host intermediate-mass black holes (IMBHs) or nearly impossible to form and retain them in their centres. Over the last decade enough theoretical and observational evidence have accumulated to believe that many galactic globular clusters may host IMBHs in their centres, just like galaxies do. The well-established correlations between the supermassive black holes and their host galaxies do suggest that, in extrapolation, globular clusters (GCs) follow the same relations. Most of the attempts in search of the central black holes (BHs) are no…
For a sample of nine Galactic globular clusters we measured the inner kinematic profiles with integral-field spectroscopy that we combined with existing outer kinematic measurements and HST luminosity profiles. With this information we are able to detect the crucial rise in the velocity-dispersion profile which indicates the presence of a central black hole. In addition, N-body simulations compared to our data will give us a deeper insight in the properties of clusters with black holes and stronger selection criteria for further studies. For the first time, we obtain a homogeneous sample of gl…
The chemical processes during the Asymptotic Giant Branch (AGB) evolution of intermediate mass single stars predict most of the observations of the different populations in Globular Clusters although some important issues still need to be further clarified. In particular, to reproduce the observed anticorrelations of Na-O and Al-Mg, chemically enriched gas lost during the AGB phase of intermediate mass single stars must be mixed with matter with a pristine chemical composition. The source of this matter is still a matter of debate. Furthermore, observations reveal that a significant fraction o…
Recently, Bahramian et al. investigated a large sample of globular clusters (GCs) and found that bright intermediate polars (IPs) are a factor of 10 less frequent in GCs than in the Galactic field. We theoretically investigate here this discrepancy based on GC numerical simulations. We found that, due to disruptive dynamical interaction, there is on average a reduction of only half of bright IP progenitors, which is clearly not enough to explain the observed deficiency. However, if the rotation- and crystallization-driven dynamo scenario recently proposed by Schreiber et al. is incorporated in…
With a goal of searching for accreting intermediate-mass black holes (IMBHs), we report the results of ultra-deep Jansky VLA radio continuum observations of the cores of three Galactic globular clusters: M15, M19, and M22. We reach rms noise levels of 1.5-2.1 uJy/beam at an average frequency of 6 GHz. No sources are observed at the center of any of the clusters. For a conservative set of assumptions about the properties of the accretion, we set 3-sigma upper limits on IMBHs from 360-980 M_sun. These limits are among the most stringent obtained for any globular cluster. They add to a growing bo…
We consider the possibility of detecting intermediate-mass ($10^3-10^4 M_{\odot}$) black holes, whose existence at the centers of globular clusters is expected from optical and infrared observations, using precise pulse arrival timing for the millisecond pulsars in globular clusters known to date. For some of these pulsars closest to the cluster centers, we have calculated the expected delay times of pulses as they pass in the gravitational field of the central black hole. The detection of such a time delay by currently available instruments for the known pulsars is shown to be impossible at a…
Globular clusters may host intermediate mass black holes (IMBHs) at their centres. Here we propose a new method for their identification using millisecond pulsars (MSPs) as probes. We show that measuring the first (jerk) and second (jounce) derivatives of the accelerations of an ensemble of MSPs will let us infer the presence of an IMBH in a globular cluster better than measuring the sole accelerations. We test this concept by simulating a set of star clusters with and without a central IMBH to extract the distributions of the stellar jerks and jounces. We then apply this technique to the ense…
We discuss a new scenario for the formation of intermediate mass black holes in dense star clusters. In this scenario, intermediate mass black holes are formed as a result of dynamical interactions of hard binaries containing a stellar mass black hole, with other stars and binaries. We discuss the necessary conditions to initiate the process of intermediate mass black hole formation and the influence of an intermediate mass black hole on the host global globular cluster properties. We discuss two scenarios for intermediate mass black hole formation. The SLOW and FAST scenarios. They occur late…
The dynamical formation of black hole binaries in globular clusters that merge due to gravitational waves occurs more frequently in higher stellar density. Meanwhile, the probability to form intermediate mass black holes (IMBHs) also increases with the density. To explore the impact of the formation and growth of IMBHs on the population of stellar mass black hole binaries from globular clusters, we analyze the existing large survey of Monte-Carlo globular cluster simulation data (MOCCA SURVEY Database I). We show that the number of binary black hole mergers agrees with the prediction based on …
Using spectra obtained with the VLT/FORS2 and Gemini-S/GMOS instruments we have investigated carbon, nitrogen and sodium abundances in a sample of red giants in the Small Magellanic Cloud cluster Kron 3. The metallicity and luminosity of this cluster are comparable to those of Galactic globular clusters although with a notably younger age of $\sim$ 6.5 Gyr. Specifically we have investigated the strengths of the CH ($λ$ 4300 A) and CN ($λ$ 3800, $λ$ 4215) molecular bands finding a bimodality of CN band-strengths and a CH/CN anti-correlation. Application of spectrum synthesis techniques reveals …
Intermediate mass black holes (IMBHs) are among the most elusive objects in contemporary astrophysics. Both theoretical and observational evidence of their existence is subject of debate. Conversely, both theory and observations confirm the presence of a large population of millisecond pulsars (MSPs) with low mass companions residing in globular cluster (GC) centers. If IMBHs are common in GC centers as well, then dynamical interactions will inevitably break up many of these binaries, causing the ejection of several fast MSPs in the Galactic halo. Such population of fast halo MSPs, hard to pro…
In this paper we explore the interplay between intermediate-mass black holes (IMBHs) and their nursing globular clusters (GCs), taking advantage of over 2000 Monte Carlo GC models. We find that the average density of IMBHs sphere of influence can be uniquely connected to the host GCs luminosity and half-light radius via a fundamental plane. We propose a statistical approach to systematically identify potential Galactic GCs harbouring either an IMBH or a massive subsystem comprised of stellar BHs. Our models show that the IMBH is often bound to a stellar companion or a stellar BH, which can lea…
Finding an intermediate-mass black hole (IMBH) in a globular cluster (GC), or proving its absence, is a crucial ingredient in our understanding of galaxy formation and evolution. The challenge is to identify a unique signature of an IMBH that cannot be accounted for by other processes. Observational claims of IMBH detection are often based on analyses of the kinematics of stars, such as a rise in the velocity dispersion profile towards the centre. In this contribution we discuss the degeneracy between this IMBH signal and pressure anisotropy in the GC. We show that that by considering anisotro…
We review spectroscopic results concerning multiple stellar populations in globularclusters. The cluster initial mass is the most important parameter determining the fraction of second generation stars. The threshold for the onset of the multiple population phenomenon is 1-3x10^5 MSun. Nucleosynthesis is influenced by metallicity: Na/O and Mg/Al anti-correlations are more extended in metal-poor than in metal-rich clusters. Massive clusters are more complex systems than the smaller ones, with several populations characterized by different chemical compositions. The high Li abundance observed in…
Ibata et al. reported evidence for density and kinematic cusps in the Galactic globular cluster M54, possibly due to the presence of a 9400 solar-mass black hole. Radiative signatures of accretion onto M54's candidate intermediate-mass black hole (IMBH) could bolster the case for its existence. Analysis of new Chandra and recent Hubble Space Telescope astrometry rules out the X-ray counterpart to the candidate IMBH suggested by Ibata et al. If an IMBH exists in M54, then it has an Eddington ratio of L(0.3-8 keV) / L(Edd) < 1.4 x 10^(-10), more similar to that of the candidate IMBH in M15 than …
We present a kinematic analysis of the globular cluster systems and diffuse stellar light of four intermediate luminosity (sub-$L^{\ast}$) early-type galaxies in the Virgo cluster based on Gemini/GMOS data. Our galaxy sample is fainter ($-23.8<M_K<-22.7$) than most previous studies, nearly doubling the number of galaxies in this magnitude range that now have GC kinematics. The data for the diffuse light extends to $4R_e$, and the data for the globular clusters reaches 8--$12R_e$. We find that the kinematics in these outer regions are all different despite the fact that these four galaxies have…
Intermediate mass black holes play a critical role in understanding the evolutionary connection between stellar mass and super-massive black holes. However, to date the existence of these species of black holes remains ambiguous and their formation process is therefore unknown. It has been long suspected that black holes with masses $10^{2}-10^{4}M_{\odot}$ should form and reside in dense stellar systems. Therefore, dedicated observational campaigns have targeted globular cluster for many decades searching for signatures of these elusive objects. All candidates found in these targeted searches…
We have determined the masses and mass-to-light ratios of 50 Galactic globular clusters by comparing their velocity dispersion and surface brightness profiles against a large grid of 900 N-body simulations of star clusters of varying initial concentration, size and central black hole mass fraction. Our models follow the evolution of the clusters under the combined effects of stellar evolution and two-body relaxation allowing us to take the effects of mass segregation and energy equipartition between stars self-consistently into account. For a subset of 16 well observed clusters we also derive …
We present deep (V ~ 28.0) BV photometry obtained with the wide field channel of the Advanced Camera for Surveys on board HST for four M31 globular clusters that were identified as candidate intermediate-age (age ~ 1-9 Gyr) by various authors, based on their integrated spectra and/or broad/intermediate-band colors. Two of them (B292 and B350) display an obvious blue horizontal branch, indicating that they are as old as the oldest Galactic globulars. On the other hand, for the other two (B058 and B337), which display red horizontal branches, it was not possible either to confirm or disconfirm t…
During the last decades, much effort has been devoted to explain the discrepancy between the amount of intracluster medium (ICM) estimated from stellar evolution theories and that emerging from observations in globular clusters (GCs). One possible scenario is the accretion of this medium by an intermediate-mass black hole (IMBH) at the centre of the cluster. In this work, we aim at modelling the cluster colour-excess profile as a tracer of the ICM density, both with and without an IMBH. Comparing the profiles with observations allows us to test the existence of IMBHs and their possible role in…
Self-lensing binaries in globular clusters -- predictions for ELT
Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences（尼古拉·哥白尼天文中心，波兰科学院）；School of Physics & Astronomy, University of Southampton（南安普顿大学物理与天文学学院）；School of Mathematics, Statistics, and Physics, Newcastle University（纽卡斯尔大学数学、统计与物理学院）
To investigate the dynamical properties of globular clusters, the surface brightness and kinematic data were collected and fitted to a family of lowered isothermal models called LIMEPY models. For 18 studied globular clusters, the amounts of concentration, truncation, and anisotropy were determined. In addition, the cluster mass, half-mass radius, distance, and mass-to-light ratio were also obtained. In general, LIMEPY models could describe these clusters well. Among these 18 clusters, NGC 5139, NGC 6388, and NGC 7078 were claimed to be candidates to host intermediate-mass black holes in liter…
PSR B1820$-$30A is located in the globular cluster NGC 6624 and is the closest known pulsar to the centre of any globular cluster. We present more than 25 years of high-precision timing observations of this millisecond pulsar and obtain four rotational frequency time derivative measurements. Modelling these higher-order derivatives as being due to orbital motion, we find solutions which indicate that the pulsar is in either a low-eccentricity ($0.33\lesssim e\lesssim0.4$) smaller orbit with a low mass companion (such as a main sequence star, white dwarf, neutron star, or stellar mass black hol…
The study of intermediate-mass black holes (IMBHs) is a young and promising field of research. Formed by runaway collisions of massive stars in young and dense stellar clusters, intermediate-mass black holes could still be present in the centers of globular clusters, today. Our group investigated the presence of intermediate-mass black holes for a sample of 10 Galactic globular clusters. We measured the inner kinematic profiles with integral-field spectroscopy and determined masses or upper limits of central black holes in each cluster. In combination with literature data we further studied th…
We present an astrometric study of the proper motions (PMs) in the core of the globular cluster NGC 6441. The core of this cluster has a high density and observations with current instrumentation are very challenging. We combine ground-based, high-angular-resolution NACO@VLT images with Hubble Space Telescope ACS/HRC data and measure PMs with a temporal baseline of 15 yr for about 1400 stars in the centermost 15 arcseconds of the cluster. We reach a PM precision of $\sim$30 $μ$as yr$^{-1}$ for bright, well-measured stars. Our results for the velocity dispersion are in good agreement with other…
Intermediate-mass black holes (IMBHs) are of interest in a wide range of astrophysical fields. In particular, the possibility of finding them at the centers of globular clusters has recently drawn attention. IMBHs became detectable since the quality of observational data sets, particularly those obtained with HST and with high resolution ground based spectrographs, advanced to the point where it is possible to measure velocity dispersions at a spatial resolution comparable to the size of the gravitational sphere of influence for plausible IMBH masses. We present results from ground based VLT/F…
We present the study of dynamical status of the globular cluster NGC 1851. A combination of multiwavelength space and ground-based data sets are used for the present analysis. In order to select the genuine cluster members, we used the astro-photometric data available from HST and GAIA-DR2 catalogs. The BSS radial distribution of the cluster is plotted from the center of the cluster to the outskirts. The radial distribution of BSS shows a central peak, followed by a dip at the intermediate radii (rmin ~ 90'') and a rising trend in the outskirts. We also estimated A+rh parameter as 0.391 +/- 0.…
Mergers of stellar-mass black holes were recently observed in the gravitational wave window opened by LIGO. This puts the spotlight on dense stellar systems and their ability to create intermediate-mass black holes (IMBHs) through repeated merging. Unfortunately, attempts at direct and indirect IMBH detection in star clusters in the nearby universe have proven inconclusive as of now. Indirect detection methods attempt to constrain IMBHs through their effect on star cluster photometric and kinematic observables. They are usually based on looking for a specific, physically motivated signature. W…
[abridged] Theoretical investigations have suggested the presence of Intermediate Mass Black Holes (IMBHs, with masses in the 100-10000 Msun range) in the cores of some Globular Clusters (GCs). In this paper we present the first application of a new technique to determine the presence or absence of a central IMBH in globular clusters that have reached energy equipartition via two-body relaxation. The method is based on the measurement of the radial profile for the average mass of stars in the system, using the fact that a quenching of mass segregation is expected when an IMBH is present. Here …
Spectroscopic and photometric observations show that many globular clusters host multiple stellar populations, challenging the common paradigm that globular clusters are "simple stellar populations" composed of stars of uniform age and chemical composition. The chemical abundances of second-generation (SG) stars constrain the sources of gas out of which these stars must have formed, indicating that the gas must contain matter processed through the high-temperature CNO cycle. First-generation massive Asymptotic Giant Branch (AGB) stars have been proposed as the source of this gas. In a previous…
For galaxies hosting supermassive black holes (SMBHs), it has been observed that the mass of the central black hole (M_BH) tightly correlates with the effective or central velocity dispersion (sigma) of the host galaxy. The origin of this M_BH - sigma scaling relation is assumed to lie in the merging history of the galaxies but many open questions about its origin and the behavior in different mass ranges still need to be addressed. The goal of this work is to study the black-hole scaling relations for low black-hole masses, where the regime of intermediate-mass black holes (IMBHs) in globular…
Globular clusters are an excellent laboratory for stellar population and dynamical research. Recent studies have shown that these stellar systems are not as simple as previously assumed. With multiple stellar populations as well as outer rotation and mass segregation they turn out to exhibit high complexity. This includes intermediate-mass black holes which are proposed to sit at the centers of some massive globular clusters. Today's high angular resolution ground based spectrographs allow velocity-dispersion measurements at a spatial resolution comparable to the radius of influence for plausi…
We consider the formation of binary intermediate black holes (BIMBH) in globular clusters (GC), which could happen either in situ or due to the mergers between clusters. We simulate the evolution of the BIMBH orbit (and its subsequent merger) due to stellar ejections. We also take into account the evaporation of GCs due to the tidal field of the host galaxy and two-body relaxation. Our results show that if at least $10^{-3}$ of all GCs become BIMBH hosts and the BIMBH masses are $\sim1\%$ of the GC mass, at least one of the inspiralling (or merging) BIMBHs will be detected by LISA during its 4…
Intermediate-mass black holes (IMBHs) have masses of about 100 to 100,000 solar masses. They remain elusive. Observing IMBHs in present-day globular clusters (GCs) would validate a formation channel for seed black holes in the early universe and inform event predictions for gravitational wave facilities. Reaching a large number of GCs per galaxy is key, as models predict that only a few percent will have retained their gravitational-wave fostering IMBHs. Related, many galaxies will need to be examined to establish a robust sample of IMBHs in GCs. These needs can be meet by using a next-generat…
Globular clusters display significant variations in their light-element content, pointing to the existence of a second stellar generation formed from the ejecta of an earlier generation. The nature of these internal polluters is still a matter of debate: the two most popular scenarios indicate intermediate-mass AGB stars and fast rotating massive stars. Abundances determination for some key elements can help distinguish between these competitor candidates. We present in this paper Y abundances for a sample of 103 red giant branch stars in NGC 6121. Within measurement errors, we find that the […
The formation of supermassive black holes at high redshift still remains a puzzle to astronomers. Their growth becomes reasonable only when starting from a massive seed black hole with mass of the order of 10^2 - 10^5 M_SUN. Intermediate-mass black holes (IMBHs) are therefore an important field of research. Especially the possibility of finding them in the centers of globular clusters has recently drawn attention. The search for IMBHs in the centers of globular clusters could therefore shed light on the process of black-hole formation and cluster evolution. We are investigating six galactic gl…
Globular clusters (GCs) may harbour intermediate-mass black holes (IMBHs) at their centres. In these dynamically active environments stellar-mass black holes (SBHs) sink to the center soon after formation, due to dynamical friction and start interacting among themselves and with the central IMBH. Likely, some of the SBHs will form bound systems with the IMBH. A fraction of those will be triple systems composed of binary SBHs and the IMBH acting as a third distant perturber. If the SBH binary orbit is sufficiently inclined it can develop Lidov-Kozai (LK) oscillations, which can drive the system…
We present results of a series of Monte Carlo simulations investigating the imprint of a central intermediate-mass black hole (IMBH) on the structure of a globular cluster. We investigate the three-dimensional and projected density profiles, and stellar disruption rates for idealized as well as realistic cluster models, taking into account a stellar mass spectrum and stellar evolution, and allowing for a larger, more realistic, number of stars than was previously possible with direct N-body methods. We compare our results to other N-body and Fokker-Planck simulations published previously. We f…
The recent discovery of gravitational waves has opened new horizons for physics. Current and upcoming missions, such as LIGO, VIRGO, KAGRA, and LISA, promise to shed light on black holes of every size from stellar mass (SBH) sizes up to supermassive black holes which reside in galactic nuclei. The intermediate mass black hole (IMBH) family has not been detected beyond any reasonable doubt neither directly nor indirectly. Recent analyses suggest observational evidence for the presence of IMBHs in the centers of two Galactic globular clusters. In this paper, we investigate the possibility that g…
We investigate age and metallicity distributions of bright globular clusters (GCs) in the candidate intermediate-age early-type galaxies NGC 3610, NGC 584 and NGC 3377 using a combination of new Gemini/NIRI K'-band imaging and existing optical V,I photometry from HST data. The V-I vs I-K' colour-colour diagram is found to break the age-metallicity degeneracy present in optical colours, as I-K' primarily measures a populations' metallicity and is relatively insensitive, unlike optical spectroscopy, to the effect of hot horizontal branch (HB) stars, known to be present in massive old GCs. We der…
We present a survey of globular clusters (GCs) in the massive gravitational lens cluster SMACS J0723.3-7327 at $z=0.39$ based on the early released JWST/NIRCam images. In the color-magnitude diagrams of the point sources we find clearly a rich population of intracluster GCs that spread in a wide area of the cluster. Their ages, considering the cluster redshift, are younger than 9.5 Gyr. The F200W (AB) magnitudes of these GCs, $26.5<{F200W_0} <29.5$ mag, correspond to $-15.2<{M_{F200W}} <-12.2$ mag, showing that they belong to the brightest GCs (including ultracompact dwarfs). The spatial distr…
Recently, both stellar mass-segregation and binary-fractions were uniformly measured on relatively large samples of Galactic Globular Clusters (GCs). Simulations show that both sizeable binary-star populations and Intermediate-Mass Black Holes (IMBHs) quench mass-segregation in relaxed GCs. Thus mass-segregation in GCs with a reliable binary-fraction measurement is a valuable probe to constrain IMBHs. In this paper we combine mass-segregation and binary-fraction measurements from the literature to build a sample of 33 GCs (with measured core-binary fractions), and a sample of 43 GCs (with a bi…
We very briefly discuss proposed in the literature possible scenarios for intermediate mass black holes (IMBH) formation in globular clusters. We also discuss the results of the MOCCA simulations of about 2000 models (BigSurvey) regarding the distribution of events connected with electromagnetic and gravitational radiations, namely: mass transfer on IMBH, collisions and mergers with IMBH and mergers with IMBH due to gravitational radiation. The rates of these events are very small, so their observation is very improbable.
