scholarly journals The dynamics of the globular cluster NGC 3201 out to the Jacobi radius

2021 ◽  
Vol 502 (3) ◽  
pp. 4513-4525
Author(s):  
Zhen Wan ◽  
William H Oliver ◽  
Holger Baumgardt ◽  
Geraint F Lewis ◽  
Mark Gieles ◽  
...  
Keyword(s):  
Dark Matter ◽  
Globular Cluster ◽  
Proper Motion ◽  
Globular Clusters ◽  
Velocity Dispersion ◽  
Outer Part ◽  
Dark Matter Halo ◽  
Body Model ◽  
The Difference ◽  
Tidal Tails

ABSTRACT As part of a chemodynamical survey of five nearby globular clusters with 2dF/AAOmega on the Anglo-Australian Telescope (AAT), we have obtained kinematic information for the globular cluster NGC 3201. Our new observations confirm the presence of a significant velocity gradient across the cluster which can almost entirely be explained by the high proper motion of the cluster (${\sim}9\, \mathrm{mas\, yr^{-1}}$). After subtracting the contribution of this perspective rotation, we found a remaining rotation signal with an amplitude of ${\sim}1\, \mathrm{km\, s^{-1}}$ around a different axis to what we expect from the tidal tails and the potential escapers, suggesting that this rotation is internal and can be a remnant of its formation process. At the outer part, we found a rotational signal that is likely a result from potential escapers. The proper motion dispersion at large radii reported by Bianchini et al. ($3.5\pm 0.9\, \mathrm{km\, s^{-1}}$) has previously been attributed to dark matter. Here, we show that the LOS dispersion between 0.5 and 1 Jacobi radius is lower ($2.01\pm 0.18\, \mathrm{km\, s^{-1}}$), yet above the predictions from an N-body model of NGC 3201 that we ran for this study ($1.48\pm 0.14\, \mathrm{km\, s^{-1}}$). Based on the simulation, we find that potential escapers cannot fully explain the observed velocity dispersion. We also estimate the effect on the velocity dispersion of different amounts of stellar-mass black holes and unbound stars from the tidal tails with varying escape rates and find that these effects cannot explain the difference between the LOS dispersion and the N-body model. Given the recent discovery of tidal tail stars at large distances from the cluster, a dark matter halo is an unlikely explanation. We show that the effect of binary stars, which is not included in the N-body model, is important and can explain part of the difference in dispersion. We speculate that the remaining difference must be the result of effects not included in the N-body model, such as initial cluster rotation, velocity anisotropy, and Galactic substructure.

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 Globular Clusters in Early-Type Galaxies with GMOS

2005 ◽  
Vol 13 ◽  
pp. 173-174
Author(s):  
Terry Bridges ◽  
Mike Beasley ◽  
Favio Faifer ◽  
Duncan Forbes ◽  
Juan Forte ◽  
...  
Keyword(s):  
Dark Matter ◽  
Globular Clusters ◽  
Velocity Dispersion ◽  
Dark Matter Halo ◽  
Early Type ◽  
Color Distribution ◽  
Local Mass

AbstractWe present recent results from our long-term Gemini/GMOS study of globular clusters (GCs) in early-type galaxies. To date, we have obtained photometry and spectroscopy for GCs in NGCs 3379, 4649, 524, 7332, and IC 1459. We find a clear bimodality in the NGC 4649 GC color distribution, with the fraction of blue/red clusters increasing with galacto-centric radius. We derive ages and metallicities for 22 GCs in NGC 3379, finding that most of the clusters appear old (10–15 Gyr); however, there is a group of 4 metal-rich, younger clusters with ages of 2–6 Gyr. The NGC 3379 GC velocity dispersion decreases with radius, as does the inferred (local) mass-to-light ratio: there is no evidence for a dark matter halo in NGC 3379 based on our GC data.

scholarly journals Mass and shape of the Milky Way’s dark matter halo with globular clusters from Gaia and Hubble

2019 ◽  
Vol 621 ◽  
pp. A56 ◽  
Author(s):  
Lorenzo Posti ◽  
Amina Helmi
Keyword(s):  
Dark Matter ◽  
Phase Space ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Cluster System ◽  
Dark Matter Halo ◽  
Proper Motions ◽  
Axis Ratio ◽  
The Galaxy ◽  
Globular Cluster System

Aims. We estimate the mass of the inner (< 20 kpc) Milky Way and the axis ratio of its inner dark matter halo using globular clusters as tracers. At the same time, we constrain the distribution in phase-space of the globular cluster system around the Galaxy. Methods. We use the Gaia Data Release 2 catalogue of 75 globular clusters’ proper motions and recent measurements of the proper motions of another 20 distant clusters obtained with the Hubble Space Telescope. We describe the globular cluster system with a distribution function (DF) with two components: a flat, rotating disc-like one and a rounder, more extended halo-like one. While fixing the Milky Way’s disc and bulge, we let the mass and shape of the dark matter halo and we fit these two parameters, together with six others describing the DF, with a Bayesian method. Results. We find the mass of the Galaxy within 20 kpc to be M(<20 kpc) = 1.91−0.17+0.18×1011 M⊙, of which MDM(<20 kpc) = 1.37−0.17+0.18×1011 M⊙ is in dark matter, and the density axis ratio of the dark matter halo to be q = 1.30 ± 0.25. Assuming a concentration-mass relation, this implies a virial mass Mvir = 1.3±0.3×1012 M⊙. Our analysis rules out oblate (q <  0.8) and strongly prolate halos (q >  1.9) with 99% probability. Our preferred model reproduces well the observed phase-space distribution of globular clusters and has a disc component that closely resembles that of the Galactic thick disc. The halo component follows a power-law density profile ρ ∝ r−3.3, has a mean rotational velocity of Vrot ≃ −14km s−1 at 20 kpc, and has a mildly radially biased velocity distribution (β ≃ 0.2 ± 0.07, which varies significantly with radius only within the inner 15 kpc). We also find that our distinction between disc and halo clusters resembles, although not fully, the observed distinction in metal-rich ([Fe/H] > −0.8) and metal-poor ([Fe/H] ≤ −0.8) cluster populations.

scholarly journals The globular cluster population of NGC 1052-DF2: evidence for rotation

2019 ◽  
Vol 491 (1) ◽  
pp. L1-L5 ◽  
Author(s):  
Geraint F Lewis ◽  
Brendon J Brewer ◽  
Zhen Wan
Keyword(s):  
Dark Matter ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Model Comparison ◽  
Velocity Dispersion ◽  
Rotational Component ◽  
Kinematic Data ◽  
Velocity Amplitude ◽  
Bayesian Model Comparison ◽  
Stellar Component

ABSTRACT Based upon the kinematics of 10 globular clusters, it has recently been claimed that the ultra-diffuse galaxy, NGC 1052-DF2, lacks a significant quantity of dark matter. Dynamical analyses have generally assumed that this galaxy is pressure supported, with the relatively small velocity dispersion of the globular cluster population indicating the deficit of dark matter. However, the presence of a significant rotation of the globular cluster population could substantially modify this conclusion. Here, we present the discovery of such a signature of rotation in the kinematics of NGC 1052-DF2’s globular clusters, with a velocity amplitude of ${\sim}12.44^{+4.40}_{-5.16}$ km s−1, which, through Bayesian model comparison, represents a marginally better fit to the available kinematic data; note that this rotation is distinct from, and approximately perpendicular to, the recently identified rotation of the stellar component of NGC 1052-DF2. Assuming this truly represents an underlying rotation, it is shown that the determined mass depends upon the inclination of the rotational component and, with a moderate inclination, the resultant mass-to-light ratio can exceed M/L ∼ 10.

scholarly journals Limits on the dark matter content of globular clusters

2009 ◽  
Vol 5 (S266) ◽  
pp. 365-365
Author(s):  
H. Baumgardt ◽  
P. Côté ◽  
M. Hilker ◽  
M. Rejkuba ◽  
S. Mieske ◽  
...  
Keyword(s):  
Dark Matter ◽  
Globular Clusters ◽  
Stellar Population ◽  
Velocity Dispersion ◽  
Large Mass ◽  
Matter Content ◽  
Dark Matter Halo ◽  
Dark Matter Halos ◽  
Galactocentric Distance ◽  
Rule Out

AbstractWe have measured the velocity dispersion of the Galactic globular cluster NGC 2419 to determine if a substantial amount of dark matter is present in this cluster. NGC 2419 is one of the best globular clusters to look for dark matter due to its large mass, long relaxation time and large Galactocentric distance, which makes tidal stripping of dark matter unlikely. Our results can be summarized as follows. (i) We found a global velocity dispersion of 4.14 ± 0.48 km s−1, which leads to a total cluster mass of (9.02 ± 2.22) × 105 M⊙ and implies a global mass-to-light ratio of 2.05 ± 0.50 M⊙/L⊙. (ii) Our derived mass-to-light ratio is completely consistent with the mass-to-light ratio of a standard stellar population at the metallicity and age of NGC 2419. In addition, the mass-to-light ratio of NGC 2419 does not increase towards the outer cluster parts. (iii) We can therefore rule out the presence of a dark-matter halo with a central density greater than about 0.02 M⊙ pc−3. Similar limits are found for other halo globular clusters, like Pal 14. These observations therefore indicate that NGC 2419 and other halo globular clusters did not form at the centers of dark-matter halos similar to those surrounding dwarf galaxies. Instead, an origin driven by gas-dynamical processes during mergers between galaxies or proto-galactic fragments seems to be the more likely explanation for the formation of even the lowest-metallicity globular clusters.

scholarly journals 2dF Spectroscopy of Globular Clusters in M104

2005 ◽  
Vol 13 ◽  
pp. 199-199
Author(s):  
Terry Bridges ◽  
Steve Zepf ◽  
Katherine Rhode ◽  
Ken Freeman
Keyword(s):  
Dark Matter ◽  
Strong Evidence ◽  
Total Mass ◽  
Globular Clusters ◽  
Total Sample ◽  
Dark Matter Halo ◽  
Large Radius ◽  
Counter Rotation ◽  
Spatial Coverage

AbstractWe have found 56 new globular clusters in M104 from 2dF multi-fiber spectroscopy, doubling the number of confirmed clusters, and extending the spatial coverage to 50 kpc radius. We find no significant rotation in the total sample, or for subsets split by color or radius. However, there are hints that the blue clusters have a higher rotation than the red clusters, and for counter-rotation of clusters at large radius. We find a total mass of M ~ 1 × 1012M⊙ and a (M/L)B =30 out to 50 kpc radius, which is strong evidence for a dark matter halo in M104.

scholarly journals Globular cluster ejection, infall, and the host dark matter halo of the Pegasus dwarf galaxy

2020 ◽  
Vol 492 (4) ◽  
pp. 5102-5120
Author(s):  
Ryan Leaman ◽  
Tomás Ruiz-Lara ◽  
Andrew A Cole ◽  
Michael A Beasley ◽  
Alina Boecker ◽  
...  
Keyword(s):  
Dark Matter ◽  
Relaxation Time ◽  
Density Profile ◽  
Globular Cluster ◽  
Dwarf Galaxy ◽  
Orbital Evolution ◽  
Dark Matter Halo ◽  
Host Galaxy ◽  
Structural Constraints ◽  
The Galaxy

ABSTRACT Recent photometric observations revealed a massive, extended (MGC ≳ 105 M⊙; Rh ∼ 14 pc) globular cluster (GC) in the central region (D3D ≲ 100 pc) of the low-mass (M* ∼ 5 × 106 M⊙) dwarf irregular galaxy Pegasus. This massive GC offers a unique opportunity to study star cluster inspiral as a mechanism for building up nuclear star clusters, and the dark matter (DM) density profile of the host galaxy. Here, we present spectroscopic observations indicating that the GC has a systemic velocity of ΔV = 3 ± 8 km s−1 relative to the host galaxy, and an old, metal-poor stellar population. We run a suite of orbital evolution models for a variety of host potentials (cored to cusped) and find that the GC’s observed tidal radius (which is ∼3 times larger than the local Jacobi radius), relaxation time, and relative velocity are consistent with it surviving inspiral from a distance of Dgal ≳ 700 pc (up to the maximum tested value of Dgal = 2000 pc). In successful trials, the GC arrives to the galaxy centre only within the last ∼1.4 ± 1 Gyr. Orbits that arrive in the centre and survive are possible in DM haloes of nearly all shapes, however to satisfy the GC’s structural constraints a galaxy DM halo with mass MDM ≃ 6 ± 2 × 109 M⊙, concentration c ≃ 13.7 ± 0.6, and an inner slope to the DM density profile of −0.9 ≤ γ ≤ −0.5 is preferred. The gas densities necessary for its creation and survival suggest the GC could have formed initially near the dwarf’s centre, but then was quickly relocated to the outskirts where the weaker tidal field permitted an increased size and relaxation time – with the latter preserving the former during subsequent orbital decay.

scholarly journals Testing dark energy models with a new sample of strong-lensing systems

2020 ◽  
Vol 498 (4) ◽  
pp. 6013-6033
Author(s):  
Mario H Amante ◽  
Juan Magaña ◽  
V Motta ◽  
Miguel A García-Aspeitia ◽  
Tomás Verdugo
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Velocity Dispersion ◽  
Cosmological Parameters ◽  
Cosmic Acceleration ◽  
Dark Matter Halo ◽  
Measured Velocity ◽  
Strong Lensing ◽  
The Impact ◽  
Einstein Radius

ABSTRACT Inspired by a new compilation of strong-lensing systems, which consist of 204 points in the redshift range 0.0625 &lt; zl &lt; 0.958 for the lens and 0.196 &lt; zs &lt; 3.595 for the source, we constrain three models that generate a late cosmic acceleration: the ω-cold dark matter model, the Chevallier–Polarski–Linder, and the Jassal–Bagla–Padmanabhan parametrizations. Our compilation contains only those systems with early-type galaxies acting as lenses, with spectroscopically measured stellar velocity dispersions, estimated Einstein radius, and both the lens and source redshifts. We assume an axially symmetric mass distribution in the lens equation, using a correction to alleviate differences between the measured velocity dispersion (σ) and the dark matter halo velocity dispersion (σDM) as well as other systematic errors that may affect the measurements. We have considered different subsamples to constrain the cosmological parameters of each model. Additionally, we generate a mock data of SLS to asses the impact of the chosen mass profile on the accuracy of Einstein radius estimation. Our results show that cosmological constraints are very sensitive to the selected data: Some cases show convergence problems in the estimation of cosmological parameters (e.g. systems with observed distance ratio Dobs &lt; 0.5), others show high values for the χ2 function (e.g. systems with a lens equation Dobs &gt; 1 or high velocity dispersion σ &gt; 276 km s−1). However, we obtained a fiduciary sample with 143 systems, which improves the constraints on each tested cosmological model.

scholarly journals Globular clusters as probes of dark matter cusp-core transformations

2019 ◽  
Vol 488 (3) ◽  
pp. 2977-2988 ◽  
Author(s):  
M D A Orkney ◽  
J I Read ◽  
J A Petts ◽  
M Gieles
Keyword(s):  
Dark Matter ◽  
Globular Clusters ◽  
Massive Star ◽  
Dwarf Galaxies ◽  
Dynamical Evolution ◽  
Dark Matter Halo ◽  
Constant Density ◽  
Ngc 6822 ◽  
Hubble Time

Abstract Bursty star formation in dwarf galaxies can slowly transform a steep dark matter cusp into a constant density core. We explore the possibility that globular clusters (GCs) retain a dynamical memory of this transformation. To test this, we use the nbody6df code to simulate the dynamical evolution of GCs, including stellar evolution, orbiting in static and time-varying potentials for a Hubble time. We find that GCs orbiting within a cored dark matter halo, or within a halo that has undergone a cusp-core transformation, grow to a size that is substantially larger (Reff &gt; 10 pc) than those in a static cusped dark matter halo. They also produce much less tidal debris. We find that the cleanest signal of an historic cusp-core transformation is the presence of large GCs with tidal debris. However, the effect is small and will be challenging to observe in real galaxies. Finally, we qualitatively compare our simulated GCs with the observed GC populations in the Fornax, NGC 6822, IKN, and Sagittarius dwarf galaxies. We find that the GCs in these dwarf galaxies are systematically larger (〈Reff〉 ≃ 7.8 pc), and have substantially more scatter in their sizes than in situ metal-rich GCs in the Milky Way and young massive star clusters forming in M83 (〈Reff〉 ≃ 2.5 pc). We show that the size, scatter, and survival of GCs in dwarf galaxies are all consistent with them having evolved in a constant density core, or a potential that has undergone a cusp-core transformation, but not in a dark matter cusp.

scholarly journals Globular Cluster Formation in Galaxy Mergers

2005 ◽  
Vol 13 ◽  
pp. 205-205
Author(s):  
Yuexing Li ◽  
Mordecai-Mark Mac Low ◽  
Ralf S. Klessen
Keyword(s):  
High Resolution ◽  
Equation Of State ◽  
Globular Cluster ◽  
Orbital Period ◽  
Globular Clusters ◽  
Cluster Formation ◽  
Galaxy Mergers ◽  
Barotropic Equation ◽  
Tidal Tails ◽  
Resolution Simulation

AbstractWe present preliminary results of a high resolution simulation of globular cluster formation in a galaxy merger using GADGET (Springel et al. 2001). A barotropic equation of state (Li et al 2003) is implemented to include effects of cooling and heating. After one orbital period, a dozen proto-globular clusters are identified in the tidal tails.

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