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 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 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 > 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 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 The Stellar and Dark Matter Halo of NGC 5128

2003 ◽  
Vol 209 ◽  
pp. 635-636
Author(s):  
Eric Peng ◽  
Holland Ford ◽  
Kenneth Freeman
Keyword(s):  
Dark Matter ◽  
Velocity Field ◽  
Globular Clusters ◽  
Stellar Populations ◽  
Elliptical Galaxies ◽  
Radial Velocities ◽  
Dark Matter Halo ◽  
Galaxy Halo ◽  
Kinematic Axis ◽  
Kinematic Information

Extragalactic planetary nebulae (PNe) and globular clusters (GCs) are complementary tools for obtaining kinematic information on stellar populations in the outer halos elliptical galaxies. NGC 5128, as the nearest large elliptical (D ~ 3.5 Mpc), is an excellent galaxy for halo studies. We have now identified a total of 1140 PNe, and possess radial velocities for 736 PNe at distances out to 80 and 50 kpc along the photometric axes. There is clear evidence for kinematic axis twisting (triaxiality) in the PNe velocity field. The mass of NGC 5128 continues to rise out to 80 kpc, where M(< 80 kpc) ~ 6.4 x 1011M⊙ with M80/LB ~ 20. We also conducted a new survey for GCs out to 50 and 30 kpc, and now have radial velocities for 188 GCs (125 new). Both the red and blue GC systems exhibit rotation. The red (metal-rich) GCs share a misaligned kinematic axis with the PNe. The success of this survey bodes well for future galaxy halo studies.

scholarly journals The total mass of the early-type galaxy NGC 4649 (M60)

2008 ◽  
pp. 1-7
Author(s):  
S. Samurovic ◽  
M.M. Cirkovic
Keyword(s):  
Dark Matter ◽  
Total Mass ◽  
Globular Clusters ◽  
X Rays ◽  
Early Type ◽  
X Ray ◽  
Modified Newtonian Dynamics ◽  
Newtonian Dynamics ◽  
Early Type Galaxy

In this paper the problem of the total mass and the total mass-to-light ratio of the early-type galaxy NGC 4649 (M60) is analyzed. Use is made of two independent techniques: the X-ray methodology which is based on the temperature of the X-ray halo of NGC 4649 and the tracer mass estimator (TME) which uses globular clusters (GCs) observed in this galaxy. The mass is calculated in Newtonian and Modified Newtonian Dynamics (MOND) approaches and it is found that inside 3 effective radii (Re ) there is no need for large amounts of dark matter. Beyond 3Re the dark matter starts to play important dynamical role. The possible reasons for the discrepancy between the estimates of the total mass based on X-rays and TME in the outer regions of NGC 4649 are also discussed.

scholarly journals Globular clusters and planetary nebulae kinematics and X-ray emission in the early-type galaxy NGC 5128

2006 ◽  
pp. 35-47 ◽  
Author(s):  
S. Samurovic
Keyword(s):  
Dark Matter ◽  
Total Mass ◽  
Globular Clusters ◽  
Planetary Nebulae ◽  
X Rays ◽  
X Ray ◽  
The Galaxy ◽  
The One ◽  
Early Type Galaxy ◽  
Good Agreement

The estimates of the mass of the galaxy NGC 5128 based on the different mass tracers, globular clusters (GCs) and planetary nebulae (PNe), are presented. These estimates are compared with the estimate based on the X-ray methodology and it is found that the results for the mass (and mass-to-light ratio) for all three approaches are in very good agreement interior to 25 arcmin; beyond 25 arcmin the X-rays predict the mass which is too high with respect to the one found using GCs and PNe. Some possible explanations for this discrepancy were discussed. The Jeans equation is also solved and its predictions for the velocity dispersion are then compared with the observed values, which extend to ~8 effective radii in the case of the GCs and ~15 effective radii in the case of the PNe. It is found that interior to ~25 arcmin (~5 effective radii) dark matter does not dominate because the total mass-to-light ratio in the B band in solar units is less than 10. Based on the GCs and PNe beyond ~25 arcmin the total mass-to-light ratio increases to ~14 (at ~80 arcmin) which indicates the existence of dark matter in the outer regions of NGC 5128.

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 Dark matter and no dark matter: on the halo mass of NGC 1052

2019 ◽  
Vol 489 (3) ◽  
pp. 3665-3669
Author(s):  
Duncan A Forbes ◽  
Adebusola Alabi ◽  
Jean P Brodie ◽  
Aaron J Romanowsky
Keyword(s):  
Dark Matter ◽  
Globular Clusters ◽  
Dark Matter Halo ◽  
Host Galaxy ◽  
Mass Relation ◽  
Mean Velocity ◽  
Dynamical Mass ◽  
Mass Profile ◽  
Velocity Dispersions ◽  
Internal Velocity

ABSTRACT The NGC 1052 group, and in particular the discovery of two ultra-diffuse galaxies with very low internal velocity dispersions, has been the subject of much attention recently. Here we present radial velocities for a sample of 77 globular clusters associated with NGC 1052 obtained on the Keck telescope. Their mean velocity and velocity dispersion are consistent with that of the host galaxy. Using a simple tracer mass estimator, we infer the enclosed dynamical mass and dark matter fraction of NGC 1052. Extrapolating our measurements with a Navarro–Frenk–White (NFW) mass profile we infer a total halo mass of 6.2(±0.2) × 1012 M⊙. This mass is fully consistent with that expected from the stellar mass–halo mass relation, suggesting that NGC 1052 has a normal dark matter halo mass (i.e. it is not deficient in dark matter in contrast to two ultra-diffuse galaxies in the group). We present a phase-space diagram showing the galaxies that lie within the projected virial radius (390 kpc) of NGC 1052. Finally, we briefly discuss the two dark matter-deficient galaxies (NGC 1052-DF2 and NGC 1052-DF4) and consider whether modified Newtonian dynamics (MOND) can account for their low observed internal velocity dispersions.

scholarly journals Mass of Spiral Galaxies by Means of a Maximum Disc Model

2018 ◽  
Vol 23 (2) ◽  
pp. 191-218
Author(s):  
Jerson Ivan Reina-Medrano ◽  
Framsol López-Suspes ◽  
Guillermo A González
Keyword(s):  
Dark Matter ◽  
Total Mass ◽  
Spiral Galaxies ◽  
Great Majority ◽  
The Other ◽  
Dark Matter Halo ◽  
Global Behavior ◽  
Rotation Curves ◽  
Disc Model ◽  
Major Cluster

Maximum disc mass models for a set of spiral galaxies from the Ursa Major Cluster are presented. We construct the models using the Hunther method and the particular solutions are chosen in such away that the circular velocities are adjusted very accurately to the observed rotation curves of some specific spiral galaxies. Under the maximum disc hypothesis, we consider that the rotation curves of the analyzed galaxies can be modeled with only the contribution of the disc. This implies that it is not necessary to consider the contribution of the dark matter halo in the inner part of the spiral. In this way, the models reproduce the global behavior of the rotation curves in the great majority of galaxies. Producing good adjustments to calculate the total mass of these galaxies, and yielding values of the order of 1010M0. Based on the verticalstability criterion presented by Viera & Ramos-Caro(2016), we find that all the galaxies analyzed present a vertically stable behavior.On the other hand, from the analysis of the epicyclic frequency we find that al lthe models exhibit mainly a radial stable behaviour except at the edge of the disc.

scholarly journals Dwarf Galaxies in the MATLAS Survey: Hubble Space Telescope Observations of the Globular Cluster System in the Ultra-diffuse Galaxy MATLAS-2019

2021 ◽  
Vol 923 (1) ◽  
pp. 9
Author(s):  
Oliver Müller ◽  
Patrick R. Durrell ◽  
Francine R. Marleau ◽  
Pierre-Alain Duc ◽  
Sungsoon Lim ◽  
...  
Keyword(s):  
Dark Matter ◽  
Globular Clusters ◽  
Hubble Space Telescope ◽  
Matter Content ◽  
Dark Matter Halo ◽  
Low Surface Brightness ◽  
Specific Frequency ◽  
Low Surface Brightness Galaxies ◽  
Superior Image Quality

Abstract Ultra-diffuse galaxies (UDGs) are very-low-surface-brightness galaxies with large effective radii. Spectroscopic measurements of a few UDGs have revealed a low dark-matter content based on the internal motion of stars or globular clusters (GCs). This is in contrast to the large number of GCs found for these systems, from which it would be expected to correspond to a large dark-matter halo mass. Here we present HST+ACS observations for the UDG MATLAS-2019 in the NGC 5846 group. Using the F606W and F814W filters, we trace the GC population two magnitudes below the peak of the GC luminosity function (GCLF). Employing Bayesian considerations, we identify 26 ± 6 GCs associated with the dwarf, yielding a large specific frequency of S N = 58 ± 14. We use the turnover of the GCLF to derive a distance of 21 ± 2 Mpc, which is consistent with the NGC 5846 group of galaxies. Due to the superior image quality of the HST, we are able to resolve the GCs and measure their sizes, which are consistent with the sizes of GCs around Local Group galaxies. Using the linear relation between the total mass of galaxies and of GCs, we derive a halo mass of 0.9 ± 0.2 × 1011 M ⊙ (M ⊙/L ⊙ > 1000). The high abundance of GCs, together with the small uncertainties, make MATLAS-2019 one of the most extreme UDGs, which likely sets an upper limit of the number of GCs for UDGs.

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