ALMA lensing cluster survey: Bright [CII] 158μm lines from a multiply imaged sub-L galaxy at z=6.0719

Seiji Fujimoto, Masamune Oguri, Gabriel Brammer, Yuki Yoshimura, Nicolas Laporte, Jorge González-López, Gabriel B. Caminha, Kotaro Kohno, Adi Zitrin, Johan Richard, Masami Ouchi, Franz E. Bauer, Ian Smail, Bunyo Hatsukade, Yoshiaki Ono, Vasily Kokorev, Hideki Umehata, Daniel Schaerer, Kirsten Knudsen, Fengwu SunGeorgios Magdis, Francesco Valentino, Yiping Ao, Sune Toft, Miroslava Dessauges-Zavadsky, Kazuhiro Shimasaku, Karina Caputi, Haruka Kusakabe, Kana Morokuma-Matsui, Kikuchihara Shotaro, Eiichi Egami, Minju M. Lee, Timothy Rawle, Daniel Espada

Research output: Contribution to journalArticlepeer-review

32 Scopus citations


We present bright [C II] 158 μm line detections from a strongly magnified and multiply imaged (μ ∼ 20–160) sub–L* (MUV = -19.75-+0.440.55) Lyman-break galaxy (LBG) at z = 6.0719 ± 0.0004, drawn from the ALMA Lensing Cluster Survey (ALCS). Emission lines are identified at 268.7 GHz at 8σ exactly at the positions of two multiple images of the LBG, behind the massive galaxy cluster RXCJ0600−2007. Our lens models, updated with the latest spectroscopy from VLT/MUSE, indicate that a sub region of the LBG crosses the caustic, and is lensed into a long (∼6″) arc with a local magnification of μ ∼ 160, for which the [C II] line is also significantly detected. The source plane reconstruction resolves the interstellar medium (ISM) structure, showing that the [C II] line is co-spatial with the rest-frame UV continuum at a scale of ∼300 pc. The [C II] line properties suggest that the LBG is a rotation-dominated system, whose velocity gradient explains a slight difference in redshifts between the whole LBG and its sub-region. The star formation rate (SFR)–L[CII] relations, for whole and sub-regions of the LBG, are consistent with those of local galaxies. We evaluate the lower limit of the faint-end of the [C II] luminosity function at z = 6, finding it to be consistent with predictions from semi-analytical models and from the local SFR–L[CII] relation with a SFR function at z = 6. These results imply that the local SFR–L[CII] relation is universal for a wide range of scales, including the spatially resolved ISM, the whole region of the galaxy, and the cosmic scale, even in the epoch of reionization.

Original languageEnglish
Article number99
JournalAstrophysical Journal
Issue number2
StatePublished - 20 Apr 2021

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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