The SAMI -- Fornax Dwarfs Survey II: The Stellar Mass Fundamental Plane and the Dark Matter fraction of Dwarf Galaxies

F. Sara Eftekhari, Reynier F. Peletier, Nicholas Scott, Steffen Mieske, Joss Bland-Hawthorn, Julia J. Bryant, Michele Cantiello, Scott M. Croom, Michael J. Drinkwater, Jesus Falcon-Barroso, Michael Hilker, Enrichetta Iodice, Nicola R. Napolitano, Marilena Spavone, Edwin A. Valentijn, Glenn van de Ven, Aku Venhola

We explore the kinematic scaling relations of 38 dwarf galaxies in the Fornax Cluster using observations from the SAMI integral field spectrograph. We focus on the Fundamental Plane (FP), defined by the physical properties of the objects (scale length, surface brightness and velocity dispersion) and the Stellar Mass (Fundamental) Plane, where surface brightness is replaced by stellar mass, and investigate their dynamical-to-stellar-mass ratio. We confirm earlier results that the Fornax dEs are significantly offset above the FP defined by massive, hot stellar systems. For the Stellar Mass (Fundamental) Plane, which shows much lower scatter, we find that young and old dwarf galaxies lie at about the same distance from the plane, all with comparable scatter. We introduce the perpendicular deviation of dwarf galaxies from the Stellar Mass Plane defined by giant early-types as a robust estimate of their DM fraction, and find that the faintest dwarfs are systematically offset above the plane, implying that they have a higher dark matter fraction. This result is confirmed when estimating the dynamical mass of our dEs using a virial mass estimator, tracing the onset of dark matter domination in low mass stellar systems. We find that the position of our galaxies on the Stellar Mass FP agrees with the galaxies in the Local Group. This seems to imply that the processes determining the position of dwarf galaxies on the FP depend on the environment in the same way, whether the galaxy is situated in the Local Group or in the Fornax Cluster.

Department of Astrophysics
External organisation(s)
University of Groningen, The University of Sydney, ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), European Southern Observatory (Chile), University of Queensland, Instituto de Astrofísica de Canarias, Universidad de La Laguna, European Southern Observatory (Germany), INAF Astronomical Observatory of Capodimonte , University of Oulu
Monthly Notices of the Royal Astronomical Society
Publication date
Peer reviewed
Austrian Fields of Science 2012
103003 Astronomy, 103004 Astrophysics
Portal url