The GRB 030329 host:: a blue low metallicity subluminous galaxy with intense star formation

We present broad band photometry and spectroscopic observations of the host galaxy of GRB 030329. Analysis of the spectral emission lines shows that the host is likely a low metallicity galaxy (Z similar to 0.004). The spectral energy distribution (SED) constructed with the photometric points has been fitted using synthetic and observational templates. The best SED fit is obtained with a starburst template with an age of similar to 150 Myr and an extinction A(v) similar to 0.6. We find that the GRB 030329 host galaxy is a subluminous galaxy (L similar to 0.016 L similar to) with a stellar mass of >= 10(8) M-circle dot. Three independent diagnostics, based on the restframe UV continuum, the [OII], and the Balmer emission lines, provide a consistent unextinguished star formation rate of similar to 0.6 M-circle dot yr(-1), implying a high unextinguished specific star formation rate (similar to 34 M-circle dot yr(-1) (L/L*)(-1)). We estimate that the unextinguished specific star formation rate of the GRB 030329 host is higher than similar to 93.5% of the galaxies at a similar redshift.