Radio continuum detection in blue early-type weak-emission-line galaxies

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 the Sloan Digital Sky Survey, are constrained here using 1.4-GHz radio continuum emission. The direct detection of 1.4-GHz radio continuum emission is made in eight WEL galaxies and a median stacking is performed on 57 WEL galaxies using Very Large Array (VLA) Faint Images of Radio Sky at Twenty-cm (FIRST) images. The median stacked 1.4-GHz flux density and luminosity are estimated as 79 +/- 19 mu Jy and 0.20 +/- 0.05 x 10(21) W Hz(-1), respectively. The radio far-infrared correlation in four WEL galaxies suggests that the radio continuum emission from WEL galaxies is most likely a result of star formation activities. The median SFR for WEL galaxies is estimated as 0.23 +/- 0.06 M-circle dot yr(-1), which is much less than SFRs (0.5-50 M-circle dot 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 s of similar to 100 km s(-1). This effect is most likely linked to the growth of a black hole and the suppression of star formation via active galactic nucleus (AGN) feedback. The colour differences between star-forming and WEL subtypes of blue ETGs appear to be driven to a large extent by the level of current star formation activities. In a likely scenario of an evolutionary sequence between subtypes, the observed colour distribution in blue ETGs can be explained best in terms of fast evolution through AGN feedback.