On the properties of the interstellar medium in extremely metal-poor
  blue compact dwarf galaxies. A VIMOS-IFU study of the cometary galaxy and Ly
  $\alpha$ absorber Tol 65
  In this study we present high-resolution VIsible Multi-Object Spectrograph
integral field unit spectroscopy (VIMOS-IFU) of the extremely metal-poor
HII/blue compact dwarf (BCD) galaxy Tol 65. The optical appearance of this
galaxy shows clearly a cometary morphology with a bright main body and an
extended and diffuse stellar tail. We focus on the detection of metallicity
gradients or inhomogeneities as expected if the ongoing star-formation activity
is sustained by the infall/accretion of metal-poor gas. No evidences of
significant spatial variations of abundances were found within our
uncertainties. However, our findings show a slight anticorrelation between gas
metallicity and star-formation rate at spaxel scales, in the sense that high
star-formation is found in regions of low-metallicity, but the scatter in this
relation indicates that the metals are almost fully diluted. Our observations
show the presence of extended H$\alpha$ emission in the stellar tail of the
galaxy. We estimated that the mass of the ionized gas in the tail
M(HII)$_{tail} \sim$1.7$\times$10$^5$ M$_{\odot}$ corresponds with $\sim$ 24
per cent of the total mass of the ionized gas in the galaxy. We found that the
H$\alpha$ velocity dispersion of the main body and the tail of the galaxy are
comparable with the one found in the neutral gas by previous studies. This
suggests that the ionized gas still retains the kinematic memory of its
parental cloud and likely a common origin. Finally, we suggest that the
infall/accretion of cold gas from the outskirts of the galaxy and/or minor
merger/interaction may have produced the almost flat abundance gradient and the
cometary morphology in Tol 65.
