Context :

Aims : Our aim is to extend the investigations of ultra-compact dwarf galaxies ( UCD ) beyond the well studied Fornax and Virgo clusters .

Methods : We measured spectroscopic redshifts of about 400 compact object candidates with 19.2 < V < 22.4 mag in the central region of the Centaurus galaxy cluster ( d=43Mpc ) , using 3 pointings with VIMOS @ VLT .
The luminosity range of the candidates covers the bright end of the globular cluster ( GC ) luminosity function and the luminosity regime of UCDs in Fornax and Virgo .
Within the area surveyed , our completeness is \approx 30 % .

Results : We find 27 compact objects with radial velocities consistent with them being members of Centaurus , covering an absolute magnitude range -12.2 < M _ { V } < -10.9 mag .
We do not find counterparts to the two very large and bright UCDs in Fornax and Virgo with M _ { V } = -13.5 mag , possibly due to survey incompleteness .
The compact objects ’ distribution in magnitude and space is consistent with that of the GC population .
Their kinematics and spatial distribution indicate that they are associated more to the central galaxies than to the overall cluster potential .
The compact objects have a mean metallicity consistent with that of the metal-rich globular cluster sub-population .
Compact objects with high S/N spectra exhibit solar [ \alpha /Fe ] abundances , consistent with typical dwarf elliptical galaxy values and unlike galactic bulge globular clusters .
HST based size estimates for a sub-sample of eight compact objects reveal the existence of one very large object with half-light radius r _ { h } around 30 pc , having M _ { V } = -11.6 mag ( \simeq 10 ^ { 7 } M _ { \sun } ) .
This source shows super-solar [ \alpha /Fe ] abundances .
Seven further sources are only marginally larger than typical GCs with r _ { h } in the range 4 to 10 pc .
Those sources exhibit a large scatter in [ \alpha /Fe ] abundances .

Conclusions : We consider the largest compact object found to be the only bona-fide UCD detected in our study .
In order to improve our understanding of UCDs in Centaurus , a significant increase of our survey completeness is necessary .