New Velocity Measurements of NGC 5128 Globular Clusters Out to 130 kpc: Outer Halo Kinematics, Substructure, and Dynamics*

Hughes, Allison; Sand, David J.; Seth, Anil; Strader, Jay; Lidman, C.; Voggel, Karina; Dumont, Antoine; Crnojević, Denija; Mateo, Mario; Caldwell, Nelson; Forbes, Duncan A.; Pearson, Sarah; Guhathakurta, Puragra; Toloba, Elisa

doi:10.3847/1538-4357/acbf43

Cited by 6 publications

(1 citation statement)

References 109 publications

(159 reference statements)

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“…It is possible that the HST images used in this work did not capture enough of our galaxies' halos for us to detect a strong relation between GCS and environmental parameters. Recent observational studies such as Hughes et al (2023) show that accreted GCs may remain far from their new host galaxy's center, well outside the WFC3 field of view at the distance of our galaxy sample. To understand the full GCSs of our galaxies, we would need either a wider field of view or mosaic images.…”

Section: Discussion and Summarymentioning

confidence: 93%

Comparing Globular Cluster System Properties with Host Galaxy Environment*

Hartman

Harris

Blakeslee

et al. 2023

ApJ

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We present Hubble Space Telescope photometry in the optical (F475X) and near-infrared (F110W) bands of the globular cluster (GC) systems of the inner halos of a sample of 15 massive elliptical galaxies. The targets are selected from the volume-limited MASSIVE survey, and chosen to sample a range of environments from sparsely populated groups to the brightest cluster galaxies in dense clusters. We also present a quantitative model of the relation between (F475X − F110W) color and cluster metallicity [M/H], using simulated GCs. Because much of the GC population in such galaxies is built up through accretion, the metallicity distribution of the GC systems might be expected to vary with galaxy environment. The photometry is used to create a completeness-corrected metallicity distribution for each galaxy in the sample, and to fit a double Gaussian curve to each histogram in order to model the two standard red and blue subpopulations. Finally, the properties of the GC metallicity distribution are correlated against galaxy environment. We find that almost no GCS properties and host galaxy environmental properties are correlated, with the exception of a weak but consistent correlation between blue fraction and nth-nearest-neighbor surface density. The results suggest that the systemic properties of the GC systems, at least in the inner to midhalo regions, are influenced more strongly by the local environment at early times, rather than by the environmental properties we see today.

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Section: Discussion and Summarymentioning

confidence: 93%

Comparing Globular Cluster System Properties with Host Galaxy Environment*

Hartman

Harris

Blakeslee

et al. 2023

ApJ

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Investigating the dark matter halo of NGC 5128 using a discrete dynamical model

Dumont,

Seth,

Strader

et al. 2024

A&A

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As the nearest accessible massive early-type galaxy, NGC 5128 presents an exceptional opportunity to measure dark matter halo parameters for a representative elliptical galaxy. Here we take advantage of rich new observational datasets of large-radius tracers to perform dynamical modeling of NGC 5128 We used a discrete axisymmetric anisotropic Jeans approach with a total tracer population of nearly 1800 planetary nebulae, globular clusters, and dwarf satellite galaxies extending to a projected distance of $ kpc from the galaxy center to model the dynamics of NGC 5128. We find that a standard Navarro-Frenk-White (NFW) halo provides an excellent fit to nearly all the data, except for a subset of the planetary nebulae that appear to be out of virial equilibrium. The best-fit dark matter halo has a virial mass of $ M vir M odot $, and NGC 5128 appears to sit below the mean stellar mass--halo mass and globular cluster mass--halo mass relations, which both predict a halo virial mass closer to $ M vir M odot $. The inferred NFW virial concentration is $c_ vir $, which is nominally lower than $c_ vir 9$ predicted from published vir M vir $ relations, but within the $ 30<!PCT!>$ scatter found in simulations. The best-fit dark matter halo constitutes only $ of the total mass at one effective radius but $ at five effective radii. The derived halo parameters are consistent within the uncertainties for models with differing tracer populations, anisotropies, and inclinations. Our analysis highlights the value of comprehensive dynamical modeling of nearby galaxies and the importance of using multiple tracers to allow cross-checks for model robustness.

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Shapes of dark matter haloes with discrete globular cluster dynamics: The example of NGC 5128 (Centaurus A)

Veršič,

Rejkuba,

Arnaboldi

et al. 2024

A&A

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Within the Lambda cold dark matter (Lambda CDM) cosmology, dark matter haloes are expected to deviate from spherical symmetry. The particular shape of a galactic halo reflects the environment and mass assembly history of its host, as well as the nature of dark matter. Constraining halo shapes at large galactocentric distances is challenging because of the low density of luminous tracers. The well-studied massive early-type galaxy NGC 5128, also known as Centaurus A (CenA), has a large number of radial velocity measurements for globular clusters (GCs) and planetary nebulae (PNe) extending over a vast area of its extended low-surface-brightness stellar halo. In this work, we aim to determine the deviation from spherical symmetry of the dark matter halo of CenA at 5 using its GCs as kinematic tracers of the gravitational potential. We investigated the largest photometric catalogue of GC candidates in order to accurately characterise the spatial distribution of the relaxed population of GCs. To investigate the presence of non-relaxed structures in the kinematic catalogue of GCs, we used the relaxed point-symmetric velocity field as determined by the host's PNe population. We used anisotropic Jeans modelling under axisymmetric assumptions together with the Gaussian likelihood and GCs as discrete tracers. The gravitational potential is generated by flattened stellar and dark matter distributions. We leveraged the different orbital properties of the blue and red GCs ---such as rotation and velocity anisotropy--- to model both populations separately. By minimising $ we iteratively find the best-fit parameters. We find that the discrete kinematics of the GCs are consistent with being drawn from an underlying relaxed velocity field determined from PNe. The best-fit parameters of the gravitational potential recovered from the blue and red GCs separately agree well and we use them to compute the final results: $M_ $, and the flattening $q_ DM $. Both GC populations show mild rotation, with red having a slightly stronger rotational signature and radially biased orbits, and blue GCs preferring negative velocity anisotropy. An oblate or a spherical dark matter halo of NGC 5128 is strongly disfavoured by our modelling.

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New Velocity Measurements of NGC 5128 Globular Clusters Out to 130 kpc: Outer Halo Kinematics, Substructure, and Dynamics*

Cited by 6 publications

References 109 publications

Comparing Globular Cluster System Properties with Host Galaxy Environment*

Comparing Globular Cluster System Properties with Host Galaxy Environment*

Investigating the dark matter halo of NGC 5128 using a discrete dynamical model

Shapes of dark matter haloes with discrete globular cluster dynamics: The example of NGC 5128 (Centaurus A)

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