VIMOS-VLT integral field kinematics of the giant low surface brightness galaxy ESO 323-G064^*

¹ Max-Plank-Institut für Extraterrestrische Physik, Giessenbachstrae, 85741 Garching bei München, Germany e-mail: lcoccato@mpe.mpg.de
² Department of Astronomy, University of Maryland, College Park, MD 20742-2421, USA
³ Carnegie Institution of Washington, 5241 Broad Branch Road NW, Washington, DC 20015, USA
⁴ European Southern Observatory, Karl-Schwarzschild-Strae 2, 85748 Garching bei München, Germany

Received: 17 June 2008
Accepted: 12 September 2008

Abstract

Aims. We have studied the bulge and the disk kinematics of the giant low surface brightness galaxy ESO 323-G064 in order to investigate its dynamical properties and the radial mass profile of the dark matter (DM) halo.

Methods. We observed the galaxy with integral field spectroscopy (VLT/VIMOS, in IFU configuration), measured the positions of the ionized gas by fitting Gaussian functions to the [O III]4959,5007 and Hβ emission lines, and fit stellar templates to the galaxy spectra to determine velocity and velocity dispersions. We modeled the stellar kinematics in the bulge with spherical isotropic Jeans models and explored the implications of self consistent and dark matter scenarios for NFW and pseudo isothermal halos.

Results. In the bulge-dominated region, , the emission lines show multi-peaked profiles. The disk dominated region of the galaxy, , exhibits regular rotation, with a flat rotation curve that reaches 248 ± 6 km s^-1. From this we estimate the total barionic mass to be M_bar ~ 1.9 10¹¹  and the total DM halo mass to be M_DM ~ 4.8 10¹² . The stellar velocity and velocity dispersion have been measured only in the innermost ≈ 5” of the bulge, and reveal a regular rotation with an observed amplitude of 140 km s^-1 and a central dispersion of σ = 180 km s^-1. Our simple Jeans modeling shows that dark matter is needed in the central 5” to explain the kinematics of the bulge, for which we estimate a mass of ≈(7 ± 3) 10¹⁰ . However, we are not able to disentangle different DM scenarios. The computed central mass density of the bulge of ESO 323-G064 resembles the central mass density of some high surface brightness galaxies, rather than that of low surface brightness galaxies.