2013ApJ...771L..20K

We report a Plateau de Bure Interferometer search for C II 158 µm emission from HCM 6A, a lensed Lyα emitter (LAE) at z = 6.56. Our non-detections of C II 158 µm line emission and 1.2 mm radio continuum emission yield 3σ limits of L_CII< 6.4 x 10⁷ x (ΔV/100Km/s)^1/2 L_☉ for the C II 158 µm line luminosity and S_1.2 mm_< 0.68 mJy for the 1.2 mm flux density. The local conversion factor between L_ C II_and the star formation rate (SFR) yields an SFR < 4.7 M_☉/yr, ~2 times lower than that inferred from the ultraviolet (UV) continuum, suggesting that the local factor may not be applicable in high-z LAEs. The non-detection of 1.2 mm continuum emission yields a total SFR < 28 M_☉/yr; any obscured star formation is thus within a factor of two of the visible star formation. Our best-fit model to the rest-frame UV/optical spectral energy distribution of HCM 6A yields a stellar mass of 1.3x10⁹ M_☉ and an SFR of ~10 M_☉/yr, with negligible dust obscuration. We fortuitously detect CO J = 3-2 emission from a z = 0.375 galaxy in the foreground cluster A370, and obtain a CO line luminosity of L'(CO) > (8.95±0.79)x10⁸ K km/s.pc2 and a molecular gas mass of M(H₂) > (4.12±0.36)x10⁹ M_☉, for a CO-to-H₂ conversion factor of 4.6 M_☉(K.km/s.pc2)^–1.