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

摘要

We present broad band photometry and spectroscopic observations of the hostgalaxy of GRB 030329. Analysis of the spectral emission lines shows that thehost is likely a low metallicity galaxy (Z~0.004). The spectral energydistribution (SED) constructed with the photometric points has been fittedusing synthetic and observational templates. The best SED fit is obtained witha starburst template with an age of ~150 Myr and an extinction Av~0.6. We findthat the GRB 030329 host galaxy is a subluminous galaxy (L~0.016 L*) with astellar mass of >~10^8 Mo. Three independent diagnostics, based on therestframe UV continuum, the [OII], and the Balmer emission lines, provide aconsistent unextincted star formation rate of ~0.6 Mo yr^-1, implying a highunextincted specific star formation rate (~34 Mo yr^-1 (L/L*)^-1). We estimatethat the unextincted specific star formation rate of the GRB 030329 host ishigher than ~93.5% of the galaxies at a similar redshift.