2006ApJ...653L..85C

We analyze 4.5, 8, and 24 µm band Spitzer images of six gamma-ray burst host galaxies at redshifts close to 1. We constrain their star formation rates (SFRs) based on the entire available spectral energy distribution rather than the 24 µm band only. Further, we estimate their stellar masses (M_*) based on rest-frame K-band luminosities. Our sample spans a wide range of galaxy properties: derived SFRs range from less than 10 to a few hundred solar masses per year; values of M_*range from 10⁹ to 10¹⁰ M_☉ with a median of 5.6x10⁹ M_☉. Comparing the specific star formation rate (φ≡SFR/M_*) of our sample as a function of M_*to other representative types of galaxies (distant red galaxies, Lyα emitters, Lyman break galaxies, submillimeter galaxies, and z∼2 galaxies from the Great Observatories Origins Deep Survey-North field), we find that gamma-ray burst hosts are among those with the highest φ.