We present VLBA observations at 0.33 and 0.61 GHz , and VLA observations between 5 and 22 GHz , of subkiloparsec scale radio emission from Mrk 231 .
In addition to jet components clearly associated with the AGN , we also find a smooth extended component of size 100 - 1000 pc most probably related to the purported massive star forming disk in Mrk 231 .
The diffuse radio emission from the disk is found to have a steep spectrum at high frequencies , characteristic of optically thin synchrotron emission .
The required relativistic particle density in the disk can be produced by a star formation rate of 220 M _ { \odot } yr ^ { -1 } in the central kiloparsec .
At low frequencies the disk is absorbed , most likely by ionized gas with an emission measure of 8 \times 10 ^ { 5 } pc cm ^ { -6 } .
We have also identified 4 candidate radio supernovae that , if confirmed , represent direct evidence for ongoing star formation in the central kiloparsec .