M. Rejkuba, Deep VLT search for globular clusters in NGC 5128: Color-magnitude diagrams and globular cluster luminosity function, ASTRON ASTR, 369(3), 2001, pp. 812-825
At the distance of NGC 5128 (3.6 +/- 0.2 Mpc) it is possible to resolve glo
bular clusters with high resolution imaging from the ground, thus allowing
the globular cluster candidate selection primarily through their morphologi
cal properties. I report the discovery of 71 globular clusters in NGC 5128
on VLT UT1-FORS1 images, including the faintest members (M-V similar to -5)
known to date in this galaxy as well as in 6 previously-known clusters. U-
and V-band photometry has been measured for all the candidates and the lum
inosity function, spanning -10.1 < M-V < -4.9 and -9.3 < M-U < -3.3, constr
ucted. These are the deepest globular cluster luminosity functions in an el
liptical galaxy determined so far. The Kolmogorov-Smirnov statistics show t
hat the difference between the globular cluster luminosity functions of NGC
5128 and the MW is not larger than the difference between the ones of M 31
and the MW. The (U - V)(0) color histogram shows a bimodal distribution. F
or 23 globular clusters I obtained K-band images with SOF1 at the NTT in La
Silla. Their positions in the (U - V) vs. (V - K) color-color diagram indi
cate that they are indeed old globular clusters. Assuming that the globular
clusters in NGC 5128 span a similar age range as the ones in the Milky Way
and adopting a linear fit between the metallicity and (U - V)(0) color, th
e metal-rich clusters peak at [Fe/H] = -0.6 dex and the metal-poor ones pea
k at [Fe/H] = -1.7 dex.