Deep combination radio observations at 1.4GHz with the VLA and MERLIN have imaged a region 10 arcminutes square surrounding the Hubble Deep Field North ( HDF-N ) .
Initial studies of the weak radio source population have shown that the proportion of starburst systems increases with decreasing radio flux density with more than 70 % of radio sources being starburst in nature at flux densities less than S { { } _ { 1.4 { GHz } } } \sim 70 \mu Jy .
The recently published GOODS ACS field overlaps this area , and here we present the results of a follow-up statistical study of the very weak radio sources ( S { { } _ { 1.4 GHz } } < 40 \mu Jy ) in an 8.5 arcminute square field centred on the HDF-N which contains the region of overlap .
Radio emission at the level of a few \mu Jy are statistically detected associated with ACS galaxies brighter than a z-band magnitude of 25 .
These very faint radio sources are extended starburst systems with average radii in the range 0.6 to 0.8 arcseconds and for those with measured redshifts , radio luminosities typically several times that of the nearby well-studies starburst galaxy M82 .