The star formation rates ( SFRs ) in weak emission line ( WEL ) galaxies in a volume-limited ( 0.02 < z < 0.05 ) sample of blue early-type galaxies ( ETGs ) identified from SDSS , are constrained here using 1.4 GHz radio continuum emission .
The direct detection of 1.4 GHz radio continuum emission is made in 8 WEL galaxies and a median stacking is performed on 57 WEL galaxies using VLA FIRST images .
The median stacked 1.4 GHz flux density and luminosity are estimated as 79 \pm 19 \mu Jy and 0.20 \pm 0.05 \times 10 ^ { 21 } W Hz ^ { -1 } respectively .
The radio far-infrared correlation in 4 WEL galaxies suggests that the radio continuum emission from WEL galaxies is most likely due to star formation activities .
The median SFR for WEL galaxies is estimated as 0.23 \pm 0.06 M _ { \odot } yr ^ { -1 } , which is much less compared to SFRs ( 0.5 - 50 M _ { \odot } yr ^ { -1 } ) in purely star forming blue ETGs .
The SFRs in blue ETGs are found to be correlated with their stellar velocity dispersions ( \sigma ) and decreasing gradually beyond \sigma of \sim 100 km s ^ { -1 } .
This effect is most likely linked with the growth of black hole and suppression of star formation via AGN feedback .
The color differences between SF and WEL sub-types of blue ETGs appear to be driven to large extent by the level of current star formation activities .
In a likely scenario of an evolutionary sequence between sub-types , the observed color distribution in blue ETGs can be explained best in terms of fast evolution through AGN feedback .