Estimated distances of our M-dwarf sample versus optical-radio separation and J-band magnitude. These distances have been obtained using the relation derived by Filippazzo et al. (2015) for ultracool dwarfs. The large error bars are mainly due to uncertainty as to the spectral classification. Lower limits (3σ) on the distances are given for the two M dwarfs without a significant J-band detection. The M dwarf ILTJ1101+6507 is outside of the UHS footprint and therefore not included in this figure.