scholarly journals Kinematics of multiple stellar populations in Globular Clusters with Gaia

2019 ◽  
Vol 14 (S351) ◽  
pp. 281-284
Author(s):  
G. Cordoni ◽  
A. P. Milone ◽  
A. Mastrobuono-Battisti ◽  
A. F. Marino ◽  
E. P. Lagioia ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Velocity Dispersion ◽  
Stellar Populations ◽  
Field Of View ◽  
Large Field ◽  
Proper Motions ◽  
Physical Processes ◽  
Internal Dynamics ◽  
Data Release ◽  
First Time

AbstractThe internal dynamics of multiple stellar populations in Globular Clusters (GCs) provides unique constraints on the physical processes responsible for their formation. Specifically, the present-day kinematics of cluster stars, such as rotation and velocity dispersion, seems to be related to the initial configuration of the system. In recent work (Milone et al. 2018), we analyzed for the first time the kinematics of the different stellar populations in NGC 0104 (47 Tucanae) over a large field of view, exploiting the Gaia Data Release 2 proper motions combined with multi-band ground-based photometry. In this paper, based on the work by Cordoni et al. (2019), we extend this analysis to six GCs, namely NGC 0288, NGC 5904 (M 5), NGC 6121 (M 4), NGC 6752, NGC 6838 (M 71) and further explore NGC 0104. Among the analyzed clusters only NGC 0104 and NGC 5904 show significant rotation on the plane of the sky. Interestingly, multiple stellar populations in NGC 5904 exhibit different rotation curves.

scholarly journals The eye of Gaia on globular clusters structure: tidal tails

2020 ◽  
Vol 495 (2) ◽  
pp. 2222-2233 ◽  
Author(s):  
A Sollima
Keyword(s):  
Globular Clusters ◽  
Stellar Population ◽  
Milky Way ◽  
Field Of View ◽  
Proper Motions ◽  
Mixture Modelling ◽  
Background Density ◽  
Data Release ◽  
Observational Estimate ◽  
Tidal Tails

ABSTRACT I analyse the projected density distribution of member stars over a wide area surrounding 18 Galactic globular clusters using the photometric and astrometric information provided by the second data release of the Gaia mission. A 5D mixture modelling technique has been employed to optimally isolate the signal of the cluster stellar population from the contamination of the Galactic field, taking advantage of its different distribution in the space formed by colours, magnitudes, parallaxes, and proper motions. In 7 clusters I detect collimated overdensities at a >3σ level above the background density extending well beyond the cluster tidal radius, consistent with the distortion expected as a result of the tidal interaction with the Milky Way potential. In five of these clusters (NGC 288, NGC 2298, NGC 5139, NGC 6341, and NGC 7099) spectacular tidal tails extend up to the border of the analysed field of view at 5 deg from the centre. At large distances from the cluster centre, the orientation of the detected overdensities appears to be systematically aligned with the cluster orbital path, in agreement with the predictions of N-body simulations. The fraction of stars contained in the tidal tails of these clusters is also used to determine the first observational estimate of their present-day destruction rates.

scholarly journals Keck Cosmic Web Imager (KCWI) spectra of globular clusters and ultracompact dwarfs in the halo of M87

2020 ◽  
Vol 497 (1) ◽  
pp. 765-775
Author(s):  
Duncan A Forbes ◽  
Anna Ferré-Mateu ◽  
Mark Durré ◽  
Jean P Brodie ◽  
Aaron J Romanowsky
Keyword(s):  
Globular Clusters ◽  
Stellar Population ◽  
Velocity Dispersion ◽  
Population Analysis ◽  
Stellar Populations ◽  
Element Abundances ◽  
Dispersion Profile ◽  
Self Consistent ◽  
First Time

ABSTRACT Using the Keck Cosmic Web Imager, we obtain spectra of several globular clusters (GCs), ultracompact dwarfs (UCDs), and the inner halo starlight of M87, at a similar projected galactocentric radius of ∼5 kpc. This enables us, for the first time, to apply the same stellar population analysis to the GCs, UCDs, and starlight consistently to derive ages, metallicities, and alpha-element abundances in M87. We find evidence for a dual stellar population in the M87 halo light, i.e. an ∼80 per cent component by mass that is old and metal-rich and a ∼20 per cent component that is old but metal-poor. Two red GCs share similar stellar populations to the halo light suggesting they may have formed contemporaneously with the dominant halo component. Three UCDs, and one blue GC, have similar stellar populations, with younger mean ages, lower metallicities, and near solar alpha-element abundances. Combined with literature data, our findings are consistent with the scenario that UCDs are the remnant nucleus of a stripped galaxy. We further investigate the discrepancy in the literature for M87’s kinematics at large radii, favouring a declining velocity dispersion profile. This work has highlighted the need for more self-consistent studies of galaxy haloes.

Kinematical evolution of Globular Clusters

2019 ◽  
Vol 14 (S351) ◽  
pp. 524-527
Author(s):  
Maria A. Tiongco ◽  
Enrico Vesperini ◽  
Anna Lisa Varri
Keyword(s):  
Angular Momentum ◽  
Structural Properties ◽  
Globular Clusters ◽  
Velocity Dispersion ◽  
Three Dimensional ◽  
Stellar Populations ◽  
Velocity Space ◽  
Fundamental Understanding

AbstractWe present several results of the study of the evolution of globular clusters’ internal kinematics, as driven by two-body relaxation and the interplay between internal angular momentum and the external Galactic tidal field. Via a large suite of N-body simulations, we explored the three-dimensional velocity space of tidally perturbed clusters, by characterizing their degree of velocity dispersion anisotropy and their rotational properties. These studies have shown that a cluster’s kinematical properties contain distinct imprints of the cluster’s initial structural properties, dynamical history, and tidal environment. Building on this fundamental understanding, we then studied the dynamics of multiple stellar populations in globular clusters, with attention to the largely unexplored role of angular momentum.

scholarly journals Testing for Dark Matter in the Outskirts of Globular Clusters

2021 ◽  
Vol 922 (2) ◽  
pp. 104
Author(s):  
Raymond G. Carlberg ◽  
Carl J. Grillmair
Keyword(s):  
Dark Matter ◽  
Globular Clusters ◽  
High Probability ◽  
Velocity Dispersion ◽  
High Redshift ◽  
Dark Matter Halo ◽  
The Sun ◽  
Proper Motions ◽  
Preliminary Results ◽  
Galactic Background

Abstract The proper motions of stars in the outskirts of globular clusters are used to estimate cluster velocity dispersion profiles as far as possible within their tidal radii. We use individual color–magnitude diagrams to select high-probability cluster stars for 25 metal-poor globular clusters within 20 kpc of the Sun, 19 of which have substantial numbers of stars at large radii. Of the 19, 11 clusters have a falling velocity dispersion in the 3–6 half-mass radii range, 6 are flat, and 2 plausibly have a rising velocity dispersion. The profiles are all in the range expected from simulated clusters that started at high redshift in a zoom-in cosmological simulation. The 11 clusters with falling velocity dispersion profiles are consistent with no dark matter above the Galactic background. The six clusters with approximately flat velocity dispersion profiles could have local dark matter, but are ambiguous. The two clusters with rising velocity dispersion profiles are consistent with a remnant local dark matter halo, but need membership confirmation and detailed orbital modeling to further test these preliminary results.

scholarly journals Shadow monochromatic backlighting: Large-field high resolution X-ray shadowgraphy with improved spectral tunability

2001 ◽  
Vol 19 (2) ◽  
pp. 285-293 ◽  
Author(s):  
T.A. PIKUZ ◽  
A. YA. FAENOV ◽  
M. FRAENKEL ◽  
A. ZIGLER ◽  
F. FLORA ◽  
...  
Keyword(s):  
High Resolution ◽  
High Spatial Resolution ◽  
Field Of View ◽  
Large Field ◽  
X Ray ◽  
Traditional Scheme ◽  
Wide Range ◽  
Wide Wavelength Range ◽  
Bent Crystals ◽  
First Time

The shadow monochromatic backlighting (SMB) scheme, a modification of the well-known soft X-ray monochromatic backlighting scheme, is proposed. It is based on a spherical crystal as the dispersive element and extends the traditional scheme by allowing one to work with a wide range of Bragg angles and thus in a wide spectral range. The advantages of the new scheme are demonstrated experimentally and supported numerically by ray-tracing simulations. In the experiments, the X-ray backlighter source is a laser-produced plasma, created by the interaction of an ultrashort pulse, Ti:Sapphire laser (120 fs, 3–5 mJ, 1016 W/cm2 on target) or a short wavelength XeCl laser (10 ns, 1–2 J, 1013 W/cm2 on target) with various solid targets (Dy, Ni + Cr, BaF2). In both experiments, the X-ray sources are well localized spatially (∼20 μm) and are spectrally tunable in a relatively wide wavelength range (λ = 8–15 Å). High quality monochromatic (δλ/λ ∼ 10−5–10−3) images with high spatial resolution (up to ∼4 μm) over a large field of view (a few square millimeters) were obtained. Utilization of spherically bent crystals to obtain high-resolution, large field, monochromatic images in a wide range of Bragg angles (35° < Θ < 90°) is demonstrated for the first time.

Internal kinematics of multiple stellar populations in globular clusters

2019 ◽  
Vol 14 (S351) ◽  
pp. 324-328
Author(s):  
Mattia Libralato
Keyword(s):  
High Precision ◽  
Globular Clusters ◽  
Hubble Space Telescope ◽  
Stellar Populations ◽  
Stellar Systems ◽  
Proper Motions ◽  
Space Telescope ◽  
Formation And Evolution ◽  
Galactic Globular Clusters ◽  
Shed Light

AbstractSpectroscopy and photometry have revealed existence, complexity and properties of the multiple stellar populations (mPOPs) hosted in Galactic globular clusters. However, the conundrum of the formation and evolution of mPOPs is far from being completely exploited: the available pieces of information seem not enough to shed light on these topics. Astrometry, and in particular high-precision proper motions, can provide us the sought-after answers about how mPOPs formed and have evolved in these ancient stellar systems. In the following, I present a brief overview of the observational results on the internal kinematics of the mPOPs in some GCs thanks to Hubble Space Telescope high-precision proper motions.

scholarly journals The dynamics of an extremely young cluster probed for the first time

2009 ◽  
Vol 5 (S266) ◽  
pp. 386-389
Author(s):  
Christine Ducourant ◽  
Sylvain Bontemps ◽  
Didier Despois ◽  
Philippe André ◽  
Ramachrisna Teixeira ◽  
...  
Keyword(s):  
Velocity Field ◽  
Proper Motion ◽  
Velocity Dispersion ◽  
Open Cluster ◽  
Extended Period ◽  
Early Evolution ◽  
Proper Motions ◽  
Crucial Importance ◽  
Cluster Systems ◽  
First Time

AbstractWe present a proper-motion program that we have developed at ESO to measure, for the first time, proper motions of members of the nearby (125 pc), very young (4 × 105 yr) infrared ρ Ophiuchi cluster. Repeated imaging over an extended period will allow us to measure the global proper motion of the cluster and its velocity dispersion and will provide access to the ~ 1 km s−1 velocities for objects as faint as K = 15.7 mag. Access to the velocity field of such an extremely young cluster is of crucial importance to investigate the origin and early evolution of open cluster systems.

scholarly journals Gaia Data Release 2

2018 ◽  
Vol 616 ◽  
pp. A12 ◽  
Author(s):  
◽  
A. Helmi ◽  
F. van Leeuwen ◽  
P. J. McMillan ◽  
D. Massari ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Milky Way ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Proper Motions ◽  
Single Plane ◽  
Dwarf Spheroidal Galaxies ◽  
Orbital Parameters ◽  
Data Release ◽  
Using Data

Context. Aims. The goal of this paper is to demonstrate the outstanding quality of the second data release of the Gaia mission and its power for constraining many different aspects of the dynamics of the satellites of the Milky Way. We focus here on determining the proper motions of 75 Galactic globular clusters, nine dwarf spheroidal galaxies, one ultra-faint system, and the Large and Small Magellanic Clouds. Methods. Using data extracted from the Gaia archive, we derived the proper motions and parallaxes for these systems, as well as their uncertainties. We demonstrate that the errors, statistical and systematic, are relatively well understood. We integrated the orbits of these objects in three different Galactic potentials, and characterised their properties. We present the derived proper motions, space velocities, and characteristic orbital parameters in various tables to facilitate their use by the astronomical community. Results. Our limited and straightforward analyses have allowed us for example to (i) determine absolute and very precise proper motions for globular clusters; (ii) detect clear rotation signatures in the proper motions of at least five globular clusters; (iii) show that the satellites of the Milky Way are all on high-inclination orbits, but that they do not share a single plane of motion; (iv) derive a lower limit for the mass of the Milky Way of 9.1-2.6+6.2 × 1011 M⊙ based on the assumption that the Leo I dwarf spheroidal is bound; (v) derive a rotation curve for the Large Magellanic Cloud based solely on proper motions that is competitive with line-of-sight velocity curves, now using many orders of magnitude more sources; and (vi) unveil the dynamical effect of the bar on the motions of stars in the Large Magellanic Cloud. Conclusions. All these results highlight the incredible power of the Gaia astrometric mission, and in particular of its second data release.

scholarly journals A chromosome map to unveil stellar populations with different magnesium abundances. The case of ω Centauri

2020 ◽  
Vol 497 (3) ◽  
pp. 3846-3859
Author(s):  
A P Milone ◽  
A F Marino ◽  
A Renzini ◽  
C Li ◽  
S Jang ◽  
...  
Keyword(s):  
Globular Clusters ◽  
First Generation ◽  
Hubble Space Telescope ◽  
Stellar Populations ◽  
Stellar Content ◽  
Chemical Abundances ◽  
Chromosome Map ◽  
First Time ◽  
Host Stars

ABSTRACT Historically, photometry has been largely used to identify stellar populations [multiple populations (MPs)] in globular clusters (GCs) by using diagrams that are based on colours and magnitudes that are mostly sensitive to stars with different metallicities or different abundances of helium, carbon, nitrogen, and oxygen. In particular, the pseudo-two-colour diagram called chromosome map (ChM), allowed the identification and the characterization of MPs in about 70 GCs by using appropriate filters of the Hubble Space Telescope (HST) that are sensitive to the stellar content of He, C, N, O, and Fe. We use here high precision HST photometry from F275W, F280N, F343N, F373N, and F814W images of ω Centauri to investigate its MPs. We introduce a new ChM whose abscissa and ordinate are mostly sensitive to stellar populations with different magnesium and nitrogen, respectively, in monometallic GCs. This ChM is effective in disentangling the MPs based on their Mg chemical abundances, allowing us to explore, for the first time, possible relations between the production of these elemental species for large samples of stars in GCs. By comparing the colours of the distinct stellar populations with the colours obtained from appropriate synthetic spectra we provide ‘photometric-like’ estimates of the chemical composition of each population. Our results show that, in addition to first-generation (1G) stars, the metal-poor population of ω Cen hosts four groups of second-generation stars with different [N/Fe], namely, 2GA–D. 2GA stars share nearly the same [Mg/Fe] as the 1G, whereas 2GB, 2GC, and 2GD are Mg depleted by ∼0.15, ∼0.25, and ∼0.45 dex, respectively. We provide evidence that the metal-intermediate populations host stars with depleted [Mg/Fe].

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