VLA FF survey: star-forming galaxy radii

We find no clear dependence between the 3GHz radio size and stellar mass of SFGs, which contrasts with the positive correlation between the UV/optical size and stellar mass of galaxies. Focusing on SFGs with log(M_*_/M_{sun}_)>10, we find that the radio/UV/optical emission tends to be more compact in galaxies with high star formation rates (>=100M_{sun}_/yr), suggesting that a central, compact starburst (and/or an active galactic nucleus) resides in the most luminous galaxies of our sample.

We also find that the physical radio/UV/optical size of radio-selected SFGs with log(M_*_/M_{sun}_)>10 increases by a factor of 1.5-2 from z~3 to z~0.3, yet the radio emission remains two to three times more compact than that from the UV/optical. These findings indicate that these massive, radio-selected SFGs at 0.3<=z<=3 tend to harbor centrally enhanced star formation activity relative to their outer disks.