The Montreal Blue Galaxy Survey.III.Third List of UV-Bright Candidates

We present and discuss the latest addition of the Montreal Blue Galaxy (MBG) survey. Inspection of 59 Curtis Schmidt plates resulted in the identification of 135 new UV-bright galaxies with B < 15.5. This brings the total number of MBGs to 469. New results of the $V/V_m$ test show that our survey is complete to B = 14.7. From our most recent spectroscopic follow-up, we confirm the discovery of one new Seyfert 1 galaxy and possibly one new Seyfert 2 galaxy. We confirm also the bias of the MBG survey towards the low-excitation and metal rich Starburst Nucleus Galaxies (SBNGs). The spectral characteristics of the MBGs are similar to those of the infrared luminous IRAS galaxies. As a common characteristic, they show a mean ratio Log([NII]/H$alpha$) in excess of 0.2 dex as compared to normal disk HII regions. In general, the MBGs have lower far-infrared luminosities ($L_{IR} < 10^{11} L_{odot}$) and are nearer (z < 0.05) than the luminous IRAS galaxies. The distribution of the morphologies of the MBGs indicates a high number of early-type spirals (Sb and earlier). Nearly half of these galaxies also possess a bar. In our sample, the fraction of galaxies with bars depends on the morphology and increases towards the late-type spirals. However, if we consider only isolated galaxies, the late-type spirals show a clear tendency to be barred. Signs of a recent interaction with neighbor galaxies are obvious only in 24% of our candidates. Although this number is only a lower limit, it is nevertheless sufficiently low to suggest that in a majority of massive galaxies the burst of star formation do not depends solely on dynamical processes.