ALMA [C II] 158 μm Detection of a Redshift 7 Lensed Galaxy behind RXJ1347.1-1145

We present the results of ALMA spectroscopic follow-up of a z = 6.766 Lyα emitting galaxy behind the cluster RX J1347.1-1145. We report the detection of [C II] 158 μm line fully consistent with the Lyα redshift and with the peak of the optical emission. Given the magnification of μ = 5.0 ± 0.3, the intrinsic (corrected for lensing) luminosity of the [C II] line is L _{[C II]} = {1.4}_-0.3^+0.2× {10}⁷ {L}_⊙ , roughly ∼5 times fainter than other detections of z ∼ 7 galaxies. The result indicates that low L _{[C II]} in z ∼ 7 galaxies compared to the local counterparts might be caused by their low metallicities and/or feedback. The small velocity offset ({{Δ }}v={20}_-40⁺¹⁴⁰ {km} {{{s}}}^-1) between the Lyα and [C II] line is unusual, and may be indicative of ionizing photons escaping.

These observations are based on the following ALMA data: ADS/JAO.ALMA#2015.1.00091.S. They are also associated with programs Spitzer #90009, 60034, 00083, 50610, 03550, 40593, and HST # GO10492, GO11591, GO12104, and GO13459. Furthermore based on multi-year KECK programs.