2007ApJS..172..518C

We present observations at 1.4 and 250 GHz of the z∼5.7 Lyα emitters (LAEs) in the COSMOS field found by Murayama et al. At 1.4 GHz there are 99 LAEs in the lower noise regions of the radio field. We do not detect any individual source down to 3 σ limits of ∼30 µJy/beam at 1.4 GHz, nor do we detect a source in a stacking analysis, to a 2 σ limit of 2.5 µJy/beam. At 250 GHz we do not detect any of the 10 LAEs that are located within the central regions of the COSMOS field covered by MAMBO (20'x20') to a typical 2 σ limit of S₂₅₀<2 mJy. The radio data imply that there are no low-luminosity radio AGNs with L_1.4>6x10²⁴ W Hz^–1 in the LAE sample. The radio and millimeter observations also rule out any highly obscured, extreme starbursts in the sample, i.e., any galaxies with massive star formation rates >1500 M_☉/yr in the full sample (based on the radio data), or 500 M_☉/yr for the 10% of the LAE sample that falls in the central MAMBO field. The stacking analysis implies an upper limit to the mean massive star formation rate of ∼100 M_☉/yr.