arXiv subjects

Tadeja Veršič

Publications and source records attributed to Tadeja Veršič.

4 recordsLinked to original sources

arXiv2026

The Fornax Cluster VLT Spectroscopic Survey - V. Mass modelling of the BCG NGC 1399 out to 150 kpc

NGC 1399, the bright central galaxy of the Fornax cluster, hosts an extensive population of globular clusters (GCs) extending beyond 200 kpc into its outer halo, about 6.5 effective radii (Re). We conducted dynamical mass modelling of NGC 1399 out to 5 Re (~150 kpc), using a comprehensive radial velocity catalogue of GCs, combining data from the Fornax cluster VLT spectroscopic survey (FVSS) with prior measurements from the literature. Applying spherical Jeans equations, we performed dispersion-kurtosis modelling of NGC 1399's GC kinematics to derive its mass profile and GC orbital anisotropy. We also investigated the impact of including intra-cluster GCs in the mass modelling, selected based on spatial segregation and a velocity $σ$-clipping method. Our findings indicate that both cusp-like (NFW) and core-like (Burkert) halos can reproduce the observed kinematics of GCs. Including the intra-cluster GCs in the mass modelling yields broadly consistent mass profiles for both halo types, with the full GC sample giving a virial mass of log $\log M_{\rm vir} = 13.81 \pm 0.09~M_{\odot}$ for the NFW halo, slightly higher than the value inferred for the Burkert halo. Regardless of the dark matter halo profile adopted, we observe that the intra-cluster GCs exhibit radial anisotropy in the outskirts, especially among the blue, metal-poor GCs. These results suggest that GCs in NGC 1399's outer halo are influenced by an additional halo component associated with the galaxy cluster potential. The radial anisotropy observed in these outer-halo GCs provides strong dynamical evidence supporting their accretion from external sources, consistent with prior photometric and spectroscopic studies of GCs. This study highlights the importance of including intra-cluster GCs in dynamical mass modelling to fully account for the contribution of dark matter to the cluster gravitational potential.

astro-ph.GA↗

arXiv2024

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

Within the $Λ$CDM cosmology, dark matter haloes are expected to deviate from spherical symmetry. Constraining the halo shapes at large galactocentric distances is challenging due to the low density of luminous tracers. The well-studied early-type galaxy NGC 5128 (Centaurus A - CenA), has a large number of radial velocities for globular clusters (GCs) and planetary nebulae (PNe) of its extended stellar halo. In this work, we aim to determine the deviation from spherical symmetry of the dark matter halo of CenA at 5 $R_{\rm e}$ using its GCs as kinematic tracers. We used the largest photometric catalogue of GC candidates to accurately characterise the spatial distribution of the relaxed population and investigated the presence of non-relaxed structures in the kinematic catalogue of GCs using 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 different orbital properties of the blue and red GCs to model them separately. We find that 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 the joint results are: $M_{200} = 1.86^{1.61}_{-0.69}\times 10^{12}$ M$_\odot$, $M_\star/L_{\rm B} = 2.98^{+0.96}_{-0.78}$ and the flattening $q_{\rm DM} = 1.45^{+0.78}_{-0.53}$. 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 CenA is strongly disfavoured by our modelling.

astro-ph.GA↗

arXiv2023

Total mass slopes and enclosed mass constrained by globular cluster system dynamics

The goal of this work is to probe the total mass distribution of early-type galaxies with globular clusters (GCs) as kinematic tracers, by constraining the parameters of the profile with a flexible modelling approach. To that end, we leverage the extended spatial distribution of GCs from the SLUGGS survey ($\langle R_{\rm GC,\ max} \rangle \sim 8R_{\rm e}$) in combination with discrete dynamical modelling. We use discrete Jeans anisotropic modelling in cylindrical coordinates to determine the velocity moments at the location of the GCs in our sample. We use a Bayesian framework to determine the best-fit parameters of the total mass density profile and orbital properties of the GC systems. We find that the orbital properties (anisotropy and rotation of the dispersion-dominated GC systems) minimally impact the measurements of the inner slope and enclosed mass, while a strong presence of dynamically-distinct subpopulations or low numbers of kinematic tracers can bias the results. Owing to the large spatial extent of the tracers our method is sensitive to the intrinsic inner slope of the total mass profile and we find $\overlineα = -1.88\pm 0.01$ for 12 galaxies with robust measurements. To compare our results with literature values we fit a single power-law profile to the resulting total mass density. In the radial range 0.1-4~$R_{\rm e}$ our measured slope has a value of $\langle γ_{\rm tot}\rangle = -2.22\pm0.14$ and is in good agreement with the literature.

astro-ph.GA↗

arXiv2023

The flattening of dark matter halo of Centaurus A galaxy (NGC 5128) out to 40 kpc

Cosmological simulations predict dark matter shapes that deviate from spherical symmetry. The exact shape depends on the prescription of the simulation and the interplay between dark matter and baryons. This signature is most pronounced in the diffuse galactic haloes that can be observationally probed with planetary nebulae and globular clusters (GCs). The kinematic observations of these halo tracers support intrinsic triaxial shape for the mass generating the gravitational potential. With discrete axisymmetric modelling of GCs as the halo tracers of NGC 5128 we investigate the overall mass distribution of this nearby giant elliptical galaxy. Our modelling approach constrains $c_{200}$, $(M/L)_{\star, B}$ and inclination. We derive a preliminary $M_{200}\sim 1 \times 10^{12}$ M$_\odot$ and flattening $q_{\mathrm{DM}}\sim 1.3$ indicative of prolate/triaxial halo for NGC 5128.

astro-ph.GA↗