New wide-field u ^ { \prime } g ^ { \prime } r ^ { \prime } i ^ { \prime } z ^ { \prime } Dark Energy Camera observations centred on the nearby giant elliptical galaxy NGC 5128 covering \sim 21 { deg } ^ { 2 } are used to compile a new catalogue of \sim 3 200 globular clusters ( GCs ) .
We report 2 404 newly identified candidates , including the vast majority within \sim 140 kpc of NGC 5128 .
We find evidence for a transition at a galactocentric radius of R _ { gc } \approx 55 kpc from GCs ‘ ‘ intrinsic ’ ’ to NGC 5128 to those likely to have been accreted from dwarf galaxies or that may transition to the intra-group medium of the Centaurus A galaxy group .
We fit power-law surface number density profiles of the form \Sigma _ { N,R _ { gc } } \propto R _ { gc } ^ { \Gamma } and find that inside the transition radius , the red GCs are more centrally concentrated than the blue , with \Gamma _ { inner,red } \approx - 1.78 and \Gamma _ { inner,blue } \approx - 1.40 , respectively .
Outside this region both profiles flatten , more dramatically for the red GCs ( \Gamma _ { outer,red } \approx - 0.33 ) compared to the blue ( \Gamma _ { outer,blue } \approx - 0.61 ) , although the former is more likely to suffer contamination by background sources .
The median ( g ^ { \prime } - z ^ { \prime } ) _ { 0 } = 1.27 mag colour of the inner red population is consistent with arising from the amalgamation of two giant galaxies each less luminous than present-day NGC 5128 .
Both in- and out-ward of the transition radius , we find the fraction of blue GCs to dominate over the red GCs , indicating a lively history of minor-mergers .
Assuming the blue GCs to originate primarily in dwarf galaxies , we model the population required to explain them , while remaining consistent with NGC 5128 ’ s present-day spheroid luminosity .
We find that that several dozen dwarfs of luminosities L _ { { dw } ,V } \simeq 10 ^ { 6 - 9.3 } L _ { V, \odot } , following a Schechter luminosity function with a faint-end slope of -1.50 \lesssim \alpha \lesssim - 1.25 is favoured , many of which may have already been disrupted in NGC 5128 ’ s tidal field .