A SEARCH FOR C II 158 μm LINE EMISSION IN HCM 6A, A Lyα EMITTER AT z=6.56

We report a Plateau de Bure Interferometer search for C II 158 mu m emission from HCM 6A, a lensed Ly alpha emitter (LAE) at z = 6.56. Our non-detections of C II 158 mu m line emission and 1.2 mm radio continuum emission yield 3 sigma limits of L-CII < 6.4 x 10(7) x (Delta V/100 km s(-1))(1/2) L-circle dot for the C II 158 mu m line luminosity and S-1.2mm < 0.68 mJy for the 1.2 mm flux density. The local conversion factor between L-CII and the star formation rate (SFR) yields an SFR < 4.7 M-circle dot yr(-1), approximate to 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-circle dot yr(-1); 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 1.3 x 10(9) M-circle dot and an SFR of approximate to 10 M-circle dot yr(-1), 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) x 10(8) K km s(-1) pc(2) and a molecular gas mass of M(H-2) > (4.12 +/- 0.36) x 10(9) M-circle dot, for a CO-to-H-2 conversion factor of 4.6 M-circle dot (K km s(-1) pc(2))(-1).