ALMA [C ii] 158 μm Detection of a Redshift 7 Lensed Galaxy behind RX J1347.1−1145*

Author(s): Bradac, M; Garcia-Appadoo, D; Huang, KH; Vallini, L; Finney, EQ; Hoag, A; Lemaux, BC; Schmidt, KB; Treu, T; Carilli, C; Dijkstra, M; Ferrara, A; Fontana, A; Jones, T; Ryan, R; Wagg, J; Gonzalez, AH | Abstract: © 2017. The American Astronomical Society. All rights reserved. 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+0.2-0.3 × 107 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 (δv = 20+140-40 Km s-1) between the Lyα and [C ii] line is unusual, and may be indicative of ionizing photons escaping.