Sub-parsec scale imaging of Centaurus A
  At a distance of about 3.8 Mpc, the radio galaxy Centaurus A is the closest
active galaxy. Therefore it is a key target for studying the innermost regions
of active galactic nuclei (AGN). VLBI observations conducted within the
framework of the TANAMI program enable us to study the central region of the
Cen A jet with some of the highest linear resolutions ever achieved in an AGN.
This region is the likely origin of the gamma-ray emission recently detected by
the Fermi Large Area Telescope (LAT). TANAMI monitors a sample of radio and
gamma-ray selected extragalactic jets south of -30 degrees declination at 8.4
GHz and 22.3 GHz with the Australian Long Baseline Array (LBA) and the
transoceanic antennas Hartebeesthoek in South Africa, the 6 m Transportable
Integrated Geodetic Observatory (TIGO) in Chile and the 9 m German Antarctic
Receiving Station (GARS) in O'Higgins, Antarctica. The highest angular
resolution achieved at 8.4 GHz in the case of Cen A is 0.59mas x 0.978mas
(natural weighting) corresponding to a linear scale of less than 18
milliparsec.
  We show images of the first three TANAMI 8.4 GHz observation epochs of the
sub-parsec scale jet-counterjet system of Cen A. With a simultaneous 22.3 GHz
observation in 2008 November, we present a high resolution spectral index map
of the inner few milliarcseconds of the jet probing the putative emission
region of gamma-ray-photons.
