The SLUGGS Survey: Globular cluster kinematics in a "double sigma" galaxy - NGC 4473

Abstract

NGC 4473 is a so--called double sigma (2$\sigma$) galaxy, i.e. a galaxy with rare, double peaks in its 2D stellar velocity dispersion. Here, we present the globular cluster (GC) kinematics in NGC 4473 out to $\sim 10R_e$ (effective radii) using data from combined HST/ACS and Subaru/Suprime--Cam imaging and Keck/DEIMOS spectroscopy. We find that the 2$\sigma$ nature of NGC 4473 persists up to 3 $R_e$, though it becomes misaligned to the photometric major axis. We also observe a significant offset between the stellar and GC rotation amplitudes. This offset can be understood as a co--addition of counter--rotating stars producing little net stellar rotation. We identify a sharp radial transition in the GC kinematics at $\sim 4R_e$ suggesting a well defined kinematically distinct halo. In the inner region ($<4R_e$), the blue GCs rotate along the photometric major axis, but in an opposite direction to the galaxy stars and red GCs. In the outer region ($>4R_e$), the red GCs rotate in an opposite direction compared to the inner region red GCs, along the photometric major axis, while the blue GCs rotate along an axis intermediate between the major and minor photometric axes. We also find a kinematically distinct population of very red GCs in the inner region with elevated rotation amplitude and velocity dispersion. The multiple kinematic components in NGC 4473 highlight the complex formation and evolutionary history of this 2$\sigma$ galaxy, as well as a distinct transition between the inner and outer components.

13 pages, 10 figures, accepted for publication in MNRAS

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• The SLUGGS Survey: The Assembly Histories of Individual Early-type Galaxies
• Nonlinear Color-Metallicity Relations of Globular Clusters. VIII. Reproducing Color Distributions of Individual Globular Cluster Systems in the Virgo and Fornax Galaxy Clusters
• The SLUGGS Survey: Trails of SLUGGS galaxies in a modified spin-ellipticity diagram
• The SAMI Galaxy Survey: rules of behaviour for spin-ellipticity radial tracks in galaxies
• Elliptical (E) and ellicular (ES) galaxies in the M_bh-M_*,sph diagram, and a merger-driven explanation for the origin of ES galaxies, anti-truncated stellar discs in lenticular galaxies, and the Sersicification of E galaxy light profiles
• Virial models and Anisotropy of Velocity Dispersion in e-galaxies