FUV imaging of Dorado galaxies

FUV.CaF2 emission is revealed in all the Dorado galaxies observed, tracing young stellar populations in ring structures and showing tidal distortions. The Sersic index, derived by fitting the luminosity profiles, is always n<3, suggesting that the FUV.CaF2 emission originates from a disk also in early-type galaxies. The star formation rate (SFR) ranges from 0.004+/-0.001M_{sun}_/yr for [CMI2001] 4136-01 to 2.455+/-0.027M_{sun}_/yr for NGC 1566.

Most of the recent star formation is found at the periphery of the Dorado group, where most of late-type galaxies are located. For these galaxies, the ratio SFRH{alpha}/SFRFUV.CaF2 is close to 1, except for the edge-on IC 2058, similar to previously reported relations for local volume samples. For early-type galaxies, however, SFRH{alpha} is about 15 times higher than SFRFUV.

Dorado's early-type galaxies define a separate locus in SFRFUV, SFRH{alpha} space with respect to the late-type galaxies, which is well represented by the relation log(SFRFUV.CaF2)=0.70xlog(SFRH{alpha})-1.26. The disk structure of the FUV.CaF2 emitting populations discovered in all the early-types galaxies implies dissipative processes and wet merging events. The systematic discrepancy between SFRs derived from H{alpha} and FUV fluxes suggests that rejuvenation episodes in early-type galaxies cannot sustain constant star formation over ~100Myr timescales.