The Fornax Cluster VLT Spectroscopic Survey
6 affiliations
- 1Finnish Centre for Astronomy with ESO (FINCA), University of Turku
- 2Department of Physics “E. Pancini”, University of Naples Federico II
- 3European Southern Observatory
- 4Department of Astrophysics, University of Vienna
- 5INAF – Astronomical Observatory of Abruzzo
- 6INAF – Osservatorio Astronomico di Capodimonte
Abstract
NGC 1399, the bright central galaxy of the Fornax cluster, contains an extensive population of globular clusters (GCs) extending beyond 200 kpc into its outer halo, approximately 6.5 effective radii (Re). We conducted dynamical mass modelling of NGC 1399 out to 5 Re (∼150 kpc) using the most comprehensive radial velocity catalogue of GCs to date, which includes data from the Fornax cluster VLT Spectroscopic Survey (FVSS) and previous velocity 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 the orbital anisotropy of its GCs. We also investigated the impact of including intra-cluster GCs in the mass modelling, which were 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 the two halo types, with the full GC sample giving a virial mass of log Mvir = 13.81 ± 0.09 M⊙ 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 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 that they were accreted from external sources, which is 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.
Versions
Related
- The Fornax Cluster VLT Spectroscopic Survey - V. Mass modelling of the BCG NGC 1399 out to 150 kpc
- Unresolved triples in the open cluster NGC 2437 (M 46) confirmed by the KMOS VVVX-GalCen Spectroscopic Survey
- Euclid: Calibrating distances from surface brightness fluctuations with Early Release Observations of the Fornax cluster
- The extragalactic science of the KMOS VVVX-GalCen spectroscopic survey II: Discovery of a galaxy cluster at z = 0.089 behind the Galactic plane
- Unresolved triples in the open cluster NGC 2437 (M 46) confirmed by the KMOS VVVX-GalCen Spectroscopic Survey
BibTeX
@article{avinash2026fornax,
title = {{The Fornax Cluster VLT Spectroscopic Survey}},
author = {Chaturvedi Avinash and Napolitano Nicola R. and Hilker Michael and Fahrion Katja and Thater Sabine and van de Ven Glenn and Cantiello Michele and Spiniello Chiara and Paolillo Maurizio and Veršič Tadeja},
journal = {Astronomy \& Astrophysics},
year = {2026},
month = oct,
doi = {10.1051/0004-6361/202555529},
url = {https://doi.org/10.1051/0004-6361/202555529},
note = {CC BY},
}
RIS
TY - JOUR
TI - The Fornax Cluster VLT Spectroscopic Survey
AU - Chaturvedi Avinash
AU - Napolitano Nicola R.
AU - Hilker Michael
AU - Fahrion Katja
AU - Thater Sabine
AU - van de Ven Glenn
AU - Cantiello Michele
AU - Spiniello Chiara
AU - Paolillo Maurizio
AU - Veršič Tadeja
PY - 2026
DA - 2026/10/24
JO - Astronomy & Astrophysics
DO - 10.1051/0004-6361/202555529
UR - https://doi.org/10.1051/0004-6361/202555529
AB - NGC 1399, the bright central galaxy of the Fornax cluster, contains an extensive population of globular clusters (GCs) extending beyond 200 kpc into its outer halo, approximately 6.5 effective radii (Re). We conducted dynamical mass modelling of NGC 1399 out to 5 Re (∼150 kpc) using the most comprehensive radial velocity catalogue of GCs to date, which includes data from the Fornax cluster VLT Spectroscopic Survey (FVSS) and previous velocity 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 the orbital anisotropy of its GCs. We also investigated the impact of including intra-cluster GCs in the mass modelling, which were 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 the two halo types, with the full GC sample giving a virial mass of log Mvir = 13.81 ± 0.09 M⊙ 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 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 that they were accreted from external sources, which is 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.
SN - 0004-6361
SN - 1432-0746
ER -