The Extended [CII] under Construction? Observation of the Brightest High-z Lensed Star-forming Galaxy at z=6.2

Yoshinobu Fudamoto, Akio K. Inoue, Dan Coe, Brian Welch, Ana Acebron, Massimo Ricotti, Nir Mandelker, Rogier A. Windhorst, Xinfeng Xu, Yuma Sugahara, Franz E. Bauer, Maruša Bradač, Larry D. Bradley, Jose M. Diego, Michael Florian, Brenda Frye, Seiji Fujimoto, Takuya Hashimoto, Alaina Henry, Guillaume MahlerPascal A. Oesch, Swara Ravindranath, Jane Rigby, Keren Sharon, Victoria Strait, Yoichi Tamura, Michele Trenti, Eros Vanzella, Erik Zackrisson, Adi Zitrin

Research output: Contribution to journalArticlepeer-review


We present results of [C II] 158 μm emission line observations, and report the spectroscopic redshift confirmation of a strongly lensed (μ ∼ 20) star-forming galaxy, MACS0308-zD1 at z = 6.2078 ± 0.0002. The [C II] emission line is detected with a signal-to-noise ratio >6 within the rest-frame UV-bright clump of the lensed galaxy (zD1.1) and exhibits multiple velocity components; the narrow [C II] has a velocity full width half maximum (FWHM) of 110 ± 20 km s−1, while broader [C II] is seen with an FWHM of 230 ± 50 km s−1. The broader [C II] component is blueshifted (−80 ± 20 km s−1) with respect to the narrow [C II] component, and has a morphology that extends beyond the UV-bright clump. We find that, while the narrow [C II] emission is most likely associated with zD1.1, the broader component is possibly associated with a physically distinct gas component from zD1.1 (e.g., outflowing or inflowing gas). Based on the nondetection of λ158μm dust continuum, we find that MACS0308-zDl's star formation activity occurs in a dust-free environment indicated by a strong upper limit of infrared luminosity ≲9 × 108 Le. Targeting this strongly lensed faint galaxy for follow-up Atacama Large Millimeter/submillimeter Array and JWST observations will be crucial to characterize the details of typical galaxy growth in the early Universe.

Original languageEnglish (US)
Article number71
JournalAstrophysical Journal
Issue number1
StatePublished - Jan 1 2024


  • Galaxy evolution (594)
  • Galaxy formation (595)
  • Gravitational lensing (670)
  • Unified Astronomy Thesaurus concepts: High-redshift galaxies (734)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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