Globular clusters in M 104: Tracing kinematics and metallicities from the centre to the halo

¹ Department of Astrophysics, University of Vienna, Türkenschanzstraße 17, 1180 Wien, Austria
² Instituto de Astrofísica de Canarias, Calle Vía Láctea, E-38206 La Laguna, Spain
³ Departamento de Astrofísica, Universidad de La Laguna, E-38206 La Laguna, Spain
⁴ Centre for Astrophysics and Supercomputing, Swinburne University, John Street, Hawthorn VIC 3122, Australia
⁵ European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching bei München, Germany
⁶ Department of Physics, Centre for Extragalactic Astronomy, Durham University, South Road, Durham DH1 3LE, UK
⁷ Institute of Physics, Laboratory of Astrophysics, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1290 Sauverny, Switzerland
⁸ Institute of Astronomy, Madingley Rd, Cambridge CB3 0HA, UK
⁹ Visiting Fellow, Clare Hall, University of Cambridge, Cambridge, UK
¹⁰ Instituto de Física, Universidade Federal do Rio Grande do Sul (UFRGS), Av. Bento Gonçalves, 9500, Porto Alegre RS 91501-970, Brazil

^⋆ Corresponding author: katja.fahrion@univie.ac.at

Received: 9 May 2025
Accepted: 12 August 2025

Abstract

As ancient star clusters, globular clusters (GCs) are regarded as powerful tracers of galaxy evolution and assembly. Due to their brightness and compact sizes, GCs are employed to probe the kinematics and stellar population properties of galaxies, from the central regions out into the halo where the underlying stellar light becomes too faint for spectroscopic studies. In this work, we present a comprehensive study of the GC system of M 104 (NGC 4594, also known as the Sombrero galaxy) based on literature spectroscopic catalogues and newly collected data from Very Large Telescope (VLT) MUSE integral-field spectroscopy combined with multi-object spectroscopy from VLT FLAMES and OSIRIS at the Gran Telescopio de Canarias (GTC). We present a new catalogue of 499 GCs with radial velocity measurements that span from the inner disc region out to ∼70 kpc (24′). In addition to velocities, we measured metallicities from the MUSE, OSIRIS, and FLAMES spectra of 190 GCs. Together with literature values, we collected a sample of 278 metallicities. We found good agreement between the velocity and metallicity measurements of GCs observed with multiple instruments. Studying GC kinematics with a simple model confirms a decreasing velocity dispersion profile and low rotation velocities. The blue GCs appear to be more dispersion-dominated, while the red GCs follow the kinematics of the stars more closely. We find a large scatter of GC metallicities with distance from the centre, and metal-rich GCs are found over all radii. We discuss how the GC metallicity distribution with a broad metal-poor component likely reflects the complex assembly history of M 104.