Probing star formation in five of the most massive spiral galaxies observed through ASTROSAT UltraViolet Imaging Telescope

We present highly resolved and sensitive imaging of the five nearby massive spiral galaxies (with rotation velocities >300kms(-1)) observed by the UltraViolet Imaging Telescope onboard India's multiwavelength astronomy satellite ASTROSAT, along with other archival observations. These massive spirals show a far-ultraviolet star formation rate in the range of similar to 1.4 - 13.7 M(circle dot)yr(-1) and fall in the 'Green Valley' region with a specific star formation rate within similar to 10(-11.5) - 10(-10.5) yr(-1). Moreover, the mean star formation rate density of the highly resolved star-forming clumps of these objects is in the range 0.011 - 0.098 M(circle dot)yr(-1)kpc(-2), signifying localized star formation. From the spectral energy distributions, under the assumption of a delayed star formation model, we show that the star formation of these objects had peaked in the period of similar to 0.8 - 2.8 Gyr after the 'Big Bang' and the object that has experienced the peak sooner after the 'Big Bang' show relatively less star-forming activity at z similar to 0 and falls below the main-sequence relation for a stellar content of greater than or similar to 10(11)M(circle dot). We also show that these objects accumulated much of their stellar mass in the early period of evolution with similar to 31 - 42 per cent of the total stellar mass obtained in a time of (1/16) - (1/5)th the age of the Universe. We estimate that these massive objects convert their halo baryons into stars with efficiencies falling between similar to 7 and 31 per cent.