The Nature of GRB-selected Submillimeter Galaxies: Hot and Young

We present detailed fits of the spectral energy distributions (SEDs) of four submillimeter galaxies selected by the presence of a gamma-ray burst (GRB) event (GRBs 980703, 000210, 000418, and 010222). These faint ~3 mJy submillimeter emitters at redshift ~1 are characterized by an unusual combination of long- and short-wavelength properties, namely enhanced submillimeter and/or radio emission combined with optical faintness and blue colors. We exclude an active galactic nucleus as the source of long-wavelength emission. From the SED fits, we conclude that the four galaxies are young (ages <2 Gyr), highly star forming (star formation rates ~150 M_☉ yr⁻¹), low mass (stellar masses ~10¹⁰ M_☉), and dusty (dust masses ~3 × 10⁸ M_☉). Their high dust temperatures (T_d≳ 45 K) indicate that GRB host galaxies are hotter, younger, and less massive counterparts to the submillimeter-selected galaxies detected so far. Future facilities like Herschel, the James Clerk Maxwell Telescope SCUBA-2, and ALMA will test this hypothesis, enabling measurement of dust temperatures of fainter GRB-selected galaxies.