scholarly journals The interaction between supermassive black holes and globular clusters

2014 ◽  
Vol 10 (S312) ◽  
pp. 118-121
Author(s):  
Mario Spera ◽  
Manuel Arca-Sedda ◽  
Roberto Capuzzo-Dolcetta
Keyword(s):  
Globular Clusters ◽  
Star Cluster ◽  
High Mass ◽  
Host Galaxy ◽  
Formation Mechanisms ◽  
Intermediate Mass ◽  
Stellar Cluster ◽  
Hubble Sequence ◽  
Upper Limit ◽  
Almost All

AbstractAlmost all galaxies along the Hubble sequence host a compact massive object (CMO) in their center. The CMO can be either a supermassive black hole (SMBH) or a very dense stellar cluster, also known as nuclear star cluster (NSC). Generally, heavier galaxies (mass ≳ 1011 M⊙) host a central SMBH while lighter show a central NSC. Intermediate mass hosts, instead, contain both a NSC and a SMBH. One possible formation mechanisms of a NSC relies on the dry-merger (migratory) scenario, in which globular clusters (GCs) decay toward the center of the host galaxy and merge. In this framework, the absence of NSCs in high-mass galaxies can be imputed to destruction of the infalling GCs by the intense tidal field of the central SMBH. In this work, we report preliminary results of N-body simulations performed using our high-resolution, direct, code HiGPUs, to investigate the effects of a central SMBH on a single GC orbiting around it. By varying either the mass of the SMBH and the mass of the host galaxy, we derived an upper limit to the mass of the central SMBH, and thus to the mass of the host, above which the formation of a NSC is suppressed.

scholarly journals Hunting for intermediate-mass black holes in globular clusters: an astrometric study of NGC 6441

2021 ◽  
Vol 503 (1) ◽  
pp. 1490-1506
Author(s):  
Maximilian Häberle ◽  
Mattia Libralato ◽  
Andrea Bellini ◽  
Laura L Watkins ◽  
Jörg-Uwe Pott ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Velocity Dispersion ◽  
Angular Resolution ◽  
Hubble Space Telescope ◽  
High Mass ◽  
High Angular Resolution ◽  
Stellar Kinematics ◽  
Intermediate Mass ◽  
The Core ◽  
Large Telescopes

ABSTRACT 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 centremost 15 arcsec of the cluster. We reach a PM precision of ∼30 µas yr−1 for bright, well-measured stars. Our results for the velocity dispersion are in good agreement with other studies and extend already existing analyses of the stellar kinematics of NGC 6441 to its centremost region never probed before. In the innermost arcsecond of the cluster, we measure a velocity dispersion of (19.1 ± 2.0) km s−1 for evolved stars. Because of its high mass, NGC 6441 is a promising candidate for harbouring an intermediate-mass black hole (IMBH). We combine our measurements with additional data from the literature and compute dynamical models of the cluster. We find an upper limit of $M_{\rm IMBH} \lt 1.32 \times 10^4\, \textrm{M}_\odot$ but we can neither confirm nor rule out its presence. We also refine the dynamical distance of the cluster to $12.74^{+0.16}_{-0.15}$ kpc. Although the hunt for an IMBH in NGC 6441 is not yet concluded, our results show how future observations with extremely large telescopes will benefit from the long temporal baseline offered by existing high-angular-resolution data.

scholarly journals Constraining nuclear star cluster formation using MUSE-AO observations of the early-type galaxy FCC 47

2019 ◽  
Vol 628 ◽  
pp. A92 ◽  
Author(s):  
Katja Fahrion ◽  
Mariya Lyubenova ◽  
Glenn van de Ven ◽  
Ryan Leaman ◽  
Michael Hilker ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Stellar Population ◽  
High Mass ◽  
Host Galaxy ◽  
Main Body ◽  
Early Type ◽  
Cluster Galaxy ◽  
The Galaxy ◽  
Poor Population

Context. Nuclear star clusters (NSCs) are found in at least 70% of all galaxies, but their formation path is still unclear. In the most common scenarios, NSCs form in-situ from the galaxy’s central gas reservoir, through the merging of globular clusters (GCs), or through a combination of both. Aims. As the scenarios pose different expectations for angular momentum and stellar population properties of the NSC in comparison to the host galaxy and the GC system, it is necessary to characterise the stellar light, NSC, and GCs simultaneously. The large NSC (reff = 66 pc) and rich GC system of the early-type Fornax cluster galaxy FCC 47 (NGC 1336) render this galaxy an ideal laboratory to constrain NSC formation. Methods. Using Multi Unit Spectroscopic Explorer science verification data assisted by adaptive optics, we obtained maps for the stellar kinematics and stellar-population properties of FCC 47. We extracted the spectra of the central NSC and determined line-of-sight velocities of 24 GCs and metallicities of five. Results. The galaxy shows the following kinematically decoupled components (KDCs): a disk and a NSC. Our orbit-based dynamical Schwarzschild model revealed that the NSC is a distinct kinematic feature and it constitutes the peak of metallicity and old ages in FCC 47. The main body consists of two counter-rotating populations and is dominated by a more metal-poor population. The GC system is bimodal with a dominant metal-poor population and the total GC system mass is ∼17% of the NSC mass (∼7 × 108 M⊙). Conclusions. The rotation, high metallicity, and high mass of the NSC cannot be explained by GC-inspiral alone. It most likely requires additional, quickly quenched, in-situ formation. The presence of two KDCs likely are evidence of a major merger that has significantly altered the structure of FCC 47, indicating the important role of galaxy mergers in forming the complex kinematics in the galaxy-NSC system.

scholarly journals The UCD Population of the Coma Cluster

2015 ◽  
Vol 12 (S316) ◽  
pp. 253-254
Author(s):  
Kristin Chiboucas ◽  
Peter Ferguson ◽  
R. Brent Tully ◽  
David Carter ◽  
Steven Phillipps ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Massive Star ◽  
Star Clusters ◽  
High Mass ◽  
Host Galaxy ◽  
Galaxy Mergers ◽  
Coma Cluster ◽  
Large Survey ◽  
Larger Sample

AbstractUCDs are super massive star clusters found largely in dense regions but have also been found around individual galaxies and in smaller groups. Their origin is still under debate but consensus is that they formed either during major galaxy mergers as mergers of super massive star clusters, are simply the high mass end of the globular cluster luminosity function and formed in the same way as globular clusters, or that they formed from the threshing of galaxies and are remnant nuclear star clusters, which themselves may have formed from the mergers of globular star clusters within galaxies. We are attempting to disentangle these competing formation scenarios with a large survey of UCDs in the Coma cluster. Using ACS two-passband imaging from the HST/ACS Coma Cluster Treasury Survey, we are using colors and sizes to identify the UCD cluster members. With a large sample within the core region of the Coma cluster, we will use the population size, properties, and spatial distribution, and comparison with the Coma globular cluster and nuclear star cluster populations to discriminate between the threshing and globular cluster scenarios. In particular, previously we have found a possible correlation of UCD colors with host galaxy and a possible excess of UCDs around a non-central giant galaxy with an unusually large globular cluster population, both suggestive of a globular cluster origin. With a larger sample size, we are investigating whether the color correlation with host persists and whether the UCD population is consistent with, or in excess of, the bright end of the GCLF. We present initial results from the survey.

scholarly journals New insights into star cluster evolution towards energy equipartition

2021 ◽  
Vol 504 (1) ◽  
pp. L12-L16
Author(s):  
Václav Pavlík ◽  
Enrico Vesperini
Keyword(s):  
Radial Velocity ◽  
Globular Clusters ◽  
Velocity Dispersion ◽  
Tangential Velocity ◽  
Star Cluster ◽  
High Mass ◽  
Stellar Kinematics ◽  
Low Mass Stars ◽  
Velocity Anisotropy ◽  
Energy Equipartition

ABSTRACT We present the results of a study aimed at exploring the evolution towards energy equipartition in star cluster models with different initial degrees of anisotropy in the velocity distribution. Our study reveals a number of novel aspects of the cluster dynamics and shows that the rate of evolution towards energy equipartition (i) depends on the initial degree of radial velocity anisotropy – it is more rapid for more radially anisotropic systems; and (ii) differs for the radial and the tangential components of the velocity dispersion. (iii) The outermost regions of the initially isotropic system evolve towards a state of ‘inverted’ energy equipartition in which high-mass stars have a larger velocity dispersion than low-mass stars – this inversion originates from the mass dependence of the tangential velocity dispersion whereas the radial velocity dispersion shows no anomaly. Our results add new fundamental elements to the theoretical framework needed to interpret the wealth of recent and upcoming observational studies of stellar kinematics in globular clusters, and shed further light on the link between the clusters’ internal kinematics, their formation, and evolutionary history.

scholarly journals Planetary systems in a star cluster II: intermediate-mass black holes and planetary systems

2020 ◽  
Vol 497 (3) ◽  
pp. 3623-3637
Author(s):  
Francesco Flammini Dotti ◽  
M B N Kouwenhoven ◽  
Qi Shu ◽  
Wei Hao ◽  
Rainer Spurzem
Keyword(s):  
Black Holes ◽  
Star Clusters ◽  
Planetary Systems ◽  
Dynamical Evolution ◽  
Star Cluster ◽  
High Mass ◽  
Intermediate Mass ◽  
Massive Black Holes ◽  
Mass Segregation ◽  
Intermediate Mass Black Holes

ABSTRACT Most stars form in dense stellar environments. It is speculated that some dense star clusters may host intermediate-mass black holes (IMBHs), which may have formed from runaway collisions between high-mass stars, or from the mergers of less massive black holes. Here, we numerically explore the evolution of populations of planets in star clusters with an IMBH. We study the dynamical evolution of single-planet systems and free-floating planets, over a period of 100 Myr, in star clusters without an IMBH, and in clusters with a central IMBH of mass $100\, \mathrm{M}_\odot$ or $200\, \mathrm{M}_\odot$. In the central region ($r\lesssim 0.2$ pc), the IMBH’s tidal influence on planetary systems is typically 10 times stronger than the average neighbour star. For a star cluster with a $200\, \mathrm{M}_\odot$ IMBH, the region in which the IMBH’s influence is stronger within the virial radius (∼1 pc). The IMBH quenches mass segregation, and the stars in the core tend to move towards intermediate regions. The ejection rate of both stars and planets is higher when an IMBH is present. The rate at which planets are expelled from their host star rate is higher for clusters with higher IMBH masses, for t < 0.5trh, while remains mostly constant while the star cluster fills its Roche lobe, similar to a star cluster without an IMBH. The disruption rate of planetary systems is higher in initially denser clusters, and for wider planetary orbits, but this rate is substantially enhanced by the presence of a central IMBH.

scholarly journals Supernova host galaxies in the dark energy survey: I. Deep coadds, photometry, and stellar masses

2020 ◽  
Vol 495 (4) ◽  
pp. 4040-4060 ◽  
Author(s):  
P Wiseman ◽  
M Smith ◽  
M Childress ◽  
L Kelsey ◽  
A Möller ◽  
...  
Keyword(s):  
Dark Energy ◽  
High Redshift ◽  
High Mass ◽  
Host Galaxy ◽  
Formation Mechanisms ◽  
Atmospheric Conditions ◽  
Host Galaxies ◽  
Dark Energy Survey ◽  
Stellar Masses ◽  
Energy Survey

ABSTRACT The 5-yr Dark Energy Survey Supernova Programme (DES-SN) is one of the largest and deepest transient surveys to date in terms of volume and number of supernovae. Identifying and characterizing the host galaxies of transients plays a key role in their classification, the study of their formation mechanisms, and the cosmological analyses. To derive accurate host galaxy properties, we create depth-optimized coadds using single-epoch DES-SN images that are selected based on sky and atmospheric conditions. For each of the five DES-SN seasons, a separate coadd is made from the other four seasons such that each SN has a corresponding deep coadd with no contaminating SN emission. The coadds reach limiting magnitudes of order ∼27 in g band, and have a much smaller magnitude uncertainty than the previous DES-SN host templates, particularly for faint objects. We present the resulting multiband photometry of host galaxies for samples of spectroscopically confirmed type Ia (SNe Ia), core-collapse (CCSNe), and superluminous (SLSNe) as well as rapidly evolving transients (RETs) discovered by DES-SN. We derive host galaxy stellar masses and probabilistically compare stellar-mass distributions to samples from other surveys. We find that the DES spectroscopically confirmed sample of SNe Ia selects preferentially fewer high-mass hosts at high-redshift compared to other surveys, while at low redshift the distributions are consistent. DES CCSNe and SLSNe hosts are similar to other samples, while RET hosts are unlike the hosts of any other transients, although these differences have not been disentangled from selection effects.

Herbig Ae/Be stars with TGAS parallaxes in the HR diagram

2017 ◽  
Vol 12 (S330) ◽  
pp. 277-278
Author(s):  
Miguel Vioque ◽  
René D. Oudmaijer ◽  
Deborah Baines
Keyword(s):  
Main Sequence ◽  
Large Fraction ◽  
High Mass ◽  
Formation Mechanisms ◽  
Evolutionary Analysis ◽  
Be Stars ◽  
Intermediate Mass ◽  
Low Mass Stars ◽  
Low Mass ◽  
Hr Diagram

AbstractThe intermediate mass Herbig Ae/Be stars are young stars approaching the Main Sequence and are key to understanding the differences in formation mechanisms between magnetic low mass stars and non-magnetic high mass stars. A large fraction of known Herbig Ae/Be stars have TGAS parallaxes, which were used to derive luminosities and place 107 of these objects in the HR diagram, increasing the number of objects using directly determined parallaxes by a factor of 5. We also studied the characteristics of the infrared excesses of this set of Herbig Ae/Be stars and we linked our results to an evolutionary analysis.

scholarly journals MOCCA code for star cluster simulations – IV. A new scenario for intermediate mass black hole formation in globular clusters

2015 ◽  
Vol 454 (3) ◽  
pp. 3150-3165 ◽  
Author(s):  
Mirek Giersz ◽  
Nathan Leigh ◽  
Arkadiusz Hypki ◽  
Nora Lützgendorf ◽  
Abbas Askar
Keyword(s):  
Black Hole ◽  
Globular Clusters ◽  
Star Cluster ◽  
Hole Formation ◽  
Intermediate Mass ◽  
Black Hole Formation

scholarly journals From a star cluster ensemble to its formation history

2015 ◽  
Vol 12 (S316) ◽  
pp. 263-264
Author(s):  
Christine Schulz ◽  
Michael Hilker
Keyword(s):  
Globular Clusters ◽  
Dwarf Galaxies ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Galaxy Cluster ◽  
Mass Function ◽  
Star Cluster ◽  
Upper Limit ◽  
Formation History ◽  
Individual Star

AbstractThe present-day sample of ultra-compact dwarf galaxies (UCDs) and globular clusters (GCs) around NGC 1399 is interpreted to be composed of individual star cluster (SC) populations. It is assumed that such an SC population forms at a constant star-formation rate (SFR), and its mass distribution is described by the embedded cluster mass function (ECMF) up to the upper limit Mmax. The GCs and UCDs probably formed in interactions of the progenitor galaxies during the assembly of the central Fornax galaxy cluster which is why we use them as tracers of those events. After some corrections, the overall GC/UCD mass function is decomposed into separate SC populations, each described by an ECMF. Mmax of each ECMF is converted to an SFR according to the SFR-Mmax relation, revealing the SFRs reached during the assembly of galaxies in the central Fornax galaxy cluster.

scholarly journals Globular cluster clustering around ultra compact dwarf galaxies in the halo of NGC 1399

2015 ◽  
Vol 11 (S317) ◽  
pp. 365-366 ◽  
Author(s):  
Karina Voggel ◽  
Michael Hilker ◽  
Tom Richtler
Keyword(s):  
Spatial Distribution ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Large Scale ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Star Cluster ◽  
Host Galaxy ◽  
Cluster Complex ◽  
Fornax Cluster

AbstractWe tested the spatial distribution of UCDs and GCs in the halo of NGC 1399 in the Fornax cluster. In particular we tried to find out if globular clusters are more abundant in the vicinity of UCDs than what is expected from their global distribution. A local overabundance of globular clusters was found around UCDs on a scale of 1 kpc compared to what is expected from the large scale distribution of globulars in the host galaxy. This effect is stronger for the metal-poor blue GCs and weaker for the red GCs. An explanation for these clustered globulars is either that they are the remains of a GC system of an ancestor dwarf galaxy before it was stripped to its nucleus, which appears as UCD today. Alternatively these clustered GCs could have been originally part of a super star cluster complex.

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